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The progression of green technologies has driven higher future demands for valuable metals such as lithium, cobalt, nickel, and manganese, hence necessitating the recycling of lithium-containing energy storage systems. Restrategizing conventional metal recycling technologies with sustainable biological approaches can explore the potential to curtail expensive process costs and emissions of hazardous by-products. This article advocates the benefits and persuasion for future studies and applications to exploit current concepts of microbial-based metal recycling technologies as environmentally cleaner options. National Environmental Agency (NEA) National Research Foundation (NRF) Submitted/Accepted version This research/project is supported by the National Research Foundation, Singapore, and National Environment Agency, Singapore, under its Closing the Waste Loop Funding Initiative (award no. USSIF- 2018-4).

The shift towards renewable energy mix has resulted in an exponential growth of the photovoltaic (PV) industry over the past few decades. Parallelly, new recycling technology developments are required to address the incoming volume of waste as they gradually approach their end-of-life (EoL) to realize the concept of a circular economy. Typical recycling processes involve high-temperature burning for separation and release of the PV cells for metal recovery processes. However, this thermal process generates gaseous by-products that cause serious health and environmental issues. Eschewing the need for burning, we demonstrate a simple crush-and-sieve methodology to strategically aids the separation of polymeric and metallic contents. The proposed approach showcased the efficient size-selective separation and generated polymer- and metal-rich fractions. More than 90 % of the total polymer present within the studied wastes was found to be retained in larger sized-particle fractions (F1 and F2). Metal content analysis highlighted the enrichment of highly valuable silver into the smallest sized-particle fraction (F4), accounting up to 70 % and 80 % of total silver present respectively for EVAc and MP. The benefits ripe through this simple crush-and-sieve method offers an attractive pathway for PV recycling process to obtain metal-rich fractions and allow focused recovery of valuable materials through an environmentally friendlier manner. National Environmental Agency (NEA) National Research Foundation (NRF) This research/project is supported by the National Research Foundation, Singapore, and National Environment Agency, Singapore under its Closing the Waste Loop Funding Initiative (Award No. USS-IF-2018- 4).

Photoelectrochemical water splitting is one of the sustainable routes to renewable hydrogen production. One of the challenges to deploying photoelectrochemical (PEC) based electrolyzers is the difficulty in the effective capture of solar radiation as the illumination angle changes throughout the day. Herein, we demonstrate a method for the angle-independent capture of solar irradiation by using transparent 3 dimensional (3D) lattice structures as the photoanode in PEC water splitting. The transparent 3D lattice structures were fabricated by 3D printing a silica sol–gel followed by aging and sintering. These transparent 3D lattice structures were coated with a conductive indium tin oxide (ITO) thin film and a Mo-doped BiVO4 photoanode thin film by dip coating. The sheet resistance of the conductive lattice structures can reach as low as 340 Ohms per sq for ∼82% optical transmission. The 3D lattice structures furnished large volumetric current densities of 1.39 mA cm−3 which is about 2.4 times higher than a flat glass substrate (0.58 mA cm−3) at 1.23 V and 1.5 G illumination. Further, the 3D lattice structures showed no significant loss in performance due to a change in the angle of illumination, whereas the performance of the flat glass substrate was significantly affected. This work opens a new paradigm for more effective capture of solar radiation that will increase the solar to energy conversion efficiency. Ministry of Education (MOE) National Research Foundation (NRF) Published version This work was supported by the Singapore Ministry of Education (MOE) Tier 2 grant (MOE T2EP50120-00081) and Tier 1 grant (2020-T1-001-147 (RG64/20)). This research was also supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Campus of Research Excellence and Technological Enterprise (CREATE) programme

Single-metal-atom chains (SMACs), as the smallest one-dimensional structure, have intriguing physical and chemical properties. Although several SMACs have been realized so far, their controllable fabrication remains challenging due to the need to arrange single atoms in an atomically precise manner. Here we develop a chemical vapour co-deposition method to construct a wafer-scale network of platinum SMACs in atom-thin films. The obtained atomic chains possess an average length of up to ~17 nm and a high density of over 10 wt%. Interestingly, as a consequence of the electronic delocalization of platinum atoms along the chain, this atomically coherent one-dimensional channel delivers a metallic behaviour, as revealed by electronic measurements, first-principles calculations and complex network modelling. Our strategy is potentially extendable to other transition metals such as cobalt, enriching the toolbox for manufacturing SMACs and paving the way for the fundamental study of one-dimensional systems and the development of devices comprising monoatomic chains. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the support from National Research Foundation Singapore programme NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007. This work is also supported by the Ministry of Education, Singapore, under its AcRF Tier 2 (MOE2019-T2-2-105) and AcRF Tier 1 RG4/17 and RG7/18. This research is also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052). The work at NUAA was supported by the National Key Research and Development Program of China (2019YFA0705400), National Natural Science Foundation of China (11772153, 22073048), the Natural Science Foundation of Jiangsu Province (BK20190018), and a Project by the Priority Academic Program Development of Jiangsu Higher Education Institutions. W.Z. acknowledges the support of the Beijing Outstanding Young Scientist Program (BJJWZYJH01201914430039). B.T. and X.W. acknowledge the support from the Ministry of Education, Singapore (MOE2019 T1-001-113). H.Y. and M. N. acknowledge the support from the Hong Kong Research Grant Council, Hong Kong (HKRGC GRF 12300218, 12300519, 17201020, 17300021, and UGC-RMGS 207300829). H.D. acknowledges the support from German Research Foundation (DFG) under the Grant SFB917 Nanoswitches.

With the excessive consumption of non-renewable resources, the exploration of effective and durable materials is highly sought after in the field of sustainable energy conversion and storage system. In this aspect, metal-organic frameworks (MOFs) are a new class of crystalline porous organic-inorganic hybrid materials. MOFs have recently been gaining traction in energy-related fields. Owing to the coordination flexibility and multiple accessible oxidation states of vanadium ions or clusters, Vanadium-MOFs (VMOFs) possess unique structural characteristics and satisfactory electrochemical properties. Furthermore, V-MOFs derived materials also exhibit superior electrical conductivity and stability when used as electrocatalysts and electrode materials. This review summarizes the research progress of V-MOFs (inclusive of pristine V-MOFs, V/M-MOFs and POV-based MOFs) and their derivatives (vanadium oxides, carboncoated vanadium oxide, vanadium phosphate, vanadate, and other vanadium doped nanomaterials) in electrochemical energy conversion (water splitting, oxygen reduction reaction) and energy storage (supercapacitor, rechargeable battery). Future possibilities and challenges for V-MOFs and their derivatives in terms of design and synthesis are discussed. Lastly, their applications in energy-related fields are also highlighted. Ministry of Education (MOE) National Research Foundation (NRF) Published version The authors gratefully acknowledge the National Natural Science Foundation of China (Nos. 51972067, 22001021, 51802044, 51902062 and 51802043), Guangdong Natural Science Funds for Distinguished Young Scholar (No.2019B151502039), Natural Science Foundation of Jiangsu Province (No. BK20201048), Natural Science Research Project of Higher Education Institutions in Jiangsu Province (No. 20KJB150008), Singapore MOE AcRF Tier 1(No. 2020‐T1‐001‐031), the Open Fund of State Key Laboratory of Tea Plant Biology and Utilization (No.SKLTOF20190119), and the National Research Foundation of Singapore (NRF) Investigatorship (No. NRF2016NRF‐NRFI001‐22).

A highly densified electrode material is desirable to achieve large volumetric capacity. However, pores acting as ion transport channels are critical for high utilization of active material. Achieving a balance between high volume density and pore utilization remains a challenge particularly for hollow materials. Herein, capillary force is employed to convert hollow fibers to a bamboo-weaving-like flexible electrode (BWFE), in which the shrinkage of hollow space results in high compactness of the electrode. The volume of the electrode can be decreased by 96% without sacrificing the gravimetric capacity. Importantly, the conductivity of BWFE after thermal treatment can reach up to 50,500 S/m which exceeds that for most other carbon materials. Detailed mechanical analysis reveals that, due to the strong interaction between nanoribbons, Young's modulus of the electrode increases by 105 times. After SnO2 active materials is impregnated, the BWFE/SnO2 electrode exhibits an exceptionally ultrahigh volumetric capacity of 2000 mAh/cm3. Submitted/Accepted version This work was supported by the High-Quality Development Project of the Ministry of Industry and Information Technology of the People’s Republic of China (TC210H041), the Hundred Talents program, the National Natural Science Foundation of China (Grant No. 51872304), and the Ningbo S&T Innovation 2025 Major Special Program (2018B10024; 2019B10(17); 2020Z101).

Extending halide perovskites' optoelectronic properties to stimuli-responsive chromism enables switchable optoelectronics, information display, and smart window applications. Here, we demonstrate a band gap tunability (chromism) via crystal structure transformation from three-dimensional FAPbBr3 to a ⟨110⟩ oriented FAn+2PbnBr3n+2 structure using a mono-halide/cation composition (FA/Pb) tuning. Furthermore, we illustrate reversible photochromism in halide perovskite by modulating the intermediate n phase in the FAn+2PbnBr3n+2 structure, enabling greater control of the optical band gap and luminescence of a ⟨110⟩ oriented mono-halide/cation perovskite. Proton transfer reaction-mass spectroscopy carried out to precisely quantify the decomposition product reveals that the organic solvent in the film is a key contributor to the structural transformation and, therefore, the chromism in the ⟨110⟩ structure. These intermediate n phases (2 ≤ n ≤ ∞) stabilize in metastable states in the FAn+2PbnBr3n+2 system, which is accessible via strain or optical or thermal input. The structure reversibility in the ⟨110⟩ perovskite allowed us to demonstrate a class of photochromic sensors capable of self-adaptation to lighting. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version This research was funded by National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Programme (CRP Award No. NRF-CRP14-2014-03) and Ministry of Education, Singapore (MOE2019-T2-2-097).

Although Ga doping can weaken the electron phonon coupling of n-type PbTe, Ga-doped PbTe has a relatively low carrier concentration (n) and high lattice thermal conductivity (κlat), resulting in a lower figure of merit (ZT) compared with those of other top-performing n-type PbTe-based thermoelectric materials. Herein, we report the extraordinary role of Zn in enhancing the thermoelectric performance of Ga-doped PbTe. It is discovered that Zn can simultaneously improve the electronic transport properties and decrease the κlat of Ga-doped PbTe, thereby affording a record high ZTavg ~1.26 at 400–873 K, with a maximum ZT value of 1.55 at 723 K. The isoelectronic substitution of Zn for Pb in Ga-doped PbTe increases the electrical conductivity and n by inducing the nucleation and growth of Ga2Te3 in the second phase. The formation of Ga2Te3 results in nonstoichiometric and Te deficiency in the PbTe matrix, which increases the number of electron carriers. Additionally, discordant Zn and Ga atoms with the highest displacement of ~0.35 Å for Zn alloying, as well as Ga2Te3 nanocrystals ranging from 30 to 200 nm coherently embedded into the PbTe matrix effectively weaken the phonon modes and scatter heat-carrying phonons, resulting in a significant reduction in κlat. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version This study was supported primarily by the Department of Energy, Office of Science Basic Energy Sciences under grant DE-SC0014520, DOE Office of Science (sample preparation, synthesis, XRD, TE measurements, TEM measurements, DFT calculations), and Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China (2021ZZ127). The authors acknowledge the Minjiang Scholar Professorship (GXRC-21004) and the National Natural Science Foundation of China (61728401). The authors acknowledge the EPIC facility of Northwestern University’s NUANCE Center, which received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center, International Institute for Nanotechnology (IIN), Keck Foundation, State of Illinois, through the IIN; and the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and DE-AC02-05CH11231. Access to facilities for high-performance computational resources at the Northwestern University is acknowledged. The authors acknowledge Singapore MOE AcRF Tier 2 under Grant No. 2018-T2-1- 010, Singapore A*STAR project A19D9a0096, and the support from FACTs of Nanyang Technological University for sample analysis.

With ever-increasing energy consumption and continuous rise in atmospheric CO2 concentration, electrochemical reduction of CO2 into chemicals/fuels is becoming a promising yet challenging solution. Sn-based materials are identified as attractive electrocatalysts for the CO2 reduction reaction (CO2 RR) to formate but suffer from insufficient selectivity and activity, especially at large cathodic current densities. Herein, we demonstrate that Cu-doped SnS2 nanoflowers can undergo in situ dynamic restructuring to generate catalytically active S-doped Cu/Sn alloy for highly selective electrochemical CO2 RR to formate over a wide potential window. Theoretical thermodynamic analysis of reaction energetics indicates that the optimal electronic structure of the Sn active site can be regulated by both S-doping and Cu-alloying to favor formate formation, while the CO and H2 pathways will be suppressed. Our findings provide a rational strategy for electronic modulation of metal active site(s) for the design of active and selective electrocatalysts towards CO2 RR. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) We acknowledge the funding support from Singapore Ministry of Education AcRF Tier 1: RG5/20 and RG4/20; Tier 2: MOET2EP10120-0002, and Agency for Science, Technology and Research (A*Star) AME IRG: A20E5c0080.Great thanks are given to the Facility for Analysis, Characterization, Testing and Simulation (FACTS) of Nanyang Technological University, Singapore. We also like to acknowledge 111 project (D18023 ) from Zhengzhou University for their support of this work.

GeMnTe2 adopts a cubic rock salt structure and is a promising mid-temperature thermoelectric material. The pair distribution function analysis of neutron total scattering data, however, indicates that GeMnTe2 is locally distorted from the ideal rock salt structure with Ge2+ cations being discordant and displaced ∼0.3 Å off the octahedron center. By alloying GeMnTe2 with SbTe, the carrier concentration can be tuned in GeMnTe2-x%SbTe (x = 15.1), leading to converged multiple broad valence bands and a high Seebeck coefficient of >200 μV K−1 from 300 to 823 K. The system exhibits a large density-of-state effective mass of >10 me and a high weighted mobility of 80 cm2 V−1 s−1, leading to a power factor of 15 μWcm−1 K−2 at 823 K. The composition GeMnTe2-15.1%SbTe exhibits very low lattice thermal conductivity of ∼0.5 Wm−1 K−1 at 823 K, attributed to the combination of oX-centering cations in the rock salt structure, Ge/Mn positional disorder, dislocations, and abundant Ge-rich and Mn-rich nanoparticles. A ZT value of ∼1.5 can be achieved for GeMnTe2-15.1%SbTe with a ZTave of 0.96 in the temperature range of 400−823 K. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version Yan Qingyu acknowledges MOE ACRF Tier 1 RG128/21 and Singapore A*STAR project A19D9a0096.

Hybrid organo-inorganic perovskites are a well-known material in the field of optoelectronic devices. They are easy to synthesize and scale, and due to the variability of composition, their properties are tunable. Until now, a significant problem in the use of this material is the environmental instability. Changing the composition of the layers by introducing copper complexes in place of an organic layer can help reduce the material degradation rate, change the optical properties, as well as add one more degree of freedom in their variability. The structure and phase transitions of hybrid perovskite with copper paddle-wheel clusters linking perovskite layers [Cu(O2C-(CH2)3-NH3)2]PbBr4 were investigated using Raman spectroscopy under variable pressure up to 17 GPa, furthermore in the temperature range between 80 K to 373 K. The following optical properties of the material are described: photoluminescence, the dependence of absorption on pressure. Primary DFT calculations have shown that the studied material can be considered as a three-component system in which energy transfers between components are possible. Based on them, further prospects for the study and application of copper-containing perovskite are proposed.

High-entropy materials, which consist of multiple elements occupying a single sublattice in a disordered manner, have emerged as innovative material systems with various promising applications. Many macroscopic physical properties, such as electrical transport and thermal transport, are closely related to the periodic distribution of atoms. In high-entropy compounds, the long-range periodic arrangement of atoms is broken down by the disordered distribution of various elements, which would lead to changes in physical properties. Therefore, the high-entropy idea will open new avenues for designing these functional materials with promising performance and high reliability. This perspective focuses on the high-entropy strategies of thermoelectric materials, discussing how high entropy will alter their properties. The possible routes of designing high-entropy high-performance thermoelectric materials are prospected, which can also provide enlightenment for the development of high-entropy systems in other research fields. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Published version This work is supported by MOE ACRF Tier 1 RG128/21 and Singapore A*STAR project A19D9a0096.

Chemical bath deposition (CBD) is a common method to fabricate SnO2 electron-transport layers in perovskite solar cells. However, this typically requires long deposition times, a significant drawback for eventual commercialisation of perovskite solar cells. By applying ultrasonication during the chemical bath deposition process, higher rates of heterogenous nucleation were triggered which accelerated the CBD process without sacrificing coverage. Deposition times of 15min, 30min and 45min were investigated, and 30 minutes was determined to be the optimal duration for ultrasonication-assisted chemical bath deposition, with the current parameters. Ministry of Education (MOE) National Research Foundation (NRF) Published version This research was funded by National Research Foundation, Prime Minister’s Office, Singapore through the Intra-CREATE Collaborative Grant (NRF2018-ITC001-001), and Ministry of Education Tier 2 project (MOE2019-T2-2-097).

A rational design on oxygen evolution reaction (OER) catalysts is pivotal to the overall efficiency of water electrolysis. Numerous works have been devoted to understanding the cation leaching and surface reconstruction of some very active electrocatalysts, while few have been on intentionally promoting the surface in a controlled fashion. In this work, we report controllable anodic leaching of Cr in CoCr2O4 by activating the pristine material at high potential, which enables the transformation of inactive spinel CoCr2O4 into a highly active catalyst. The depletion of Cr and consumption of lattice oxygen facilitate surface defects and oxygen vacancies, exposing Co species to reconstruct into active Co oxyhydroxides differ from CoOOH. A novel mechanism with the evolution of tetrahedrally coordinated surface cation into octahedral configuration via non-concerted proton-electron transfer is proposed. This work shows the importance of controlled anodic potential in modifying the surface chemistry of electrocatalysts. Ministry of Education (MOE) Accepted version The authors thank the Facility for Analysis,Characterization, Testingand Simulation (FACTS) in Nanyang Technological Univer-sity for materials characterization.

The massive adoption of renewable energy especially photovoltaic (PVs) panel is expected to create a huge waste stream once it reaches end-of-life (EoL). Despite having the highest embodied energy, present photovoltaic recycling neglected the high purity silicon found in the PV cell. Herein, a scalable and low energy process was developed to recover pristine silicon from EoL solar panel through a process which avoids energy-intensive high temperature processes. The extracted silicon was upcycled to form lithium-ion battery anodes with performances comparable to as-purchased silicon. The anodes retained 87.5 % capacity after 200 cycles while maintaining high coulombic efficiency (>99 %) at 0.5 Ag -1 charging rate. This simple and scalable process to upcycle EoL-solar panels into high value silicon-based anode can narrow the gap towards net-zero waste economy. National Environmental Agency (NEA) National Research Foundation (NRF) Submitted/Accepted version This research/project is supported by the National Research Foundation, Singapore, and National Environment Agency, Singapore under its Closing the Waste Loop Funding Initiative (Award No. USS-IF-2018-4).

Rate capability is characterized necessarily in almost all battery-related reports, while there is no universal metric for quantitative comparison. Here, we proposed the characteristic time of diffusion, which mainly combines the effects of diffusion coefficients and geometric sizes, as an easy-to-use figure of merit (FOM) to standardize the comparison of fast-charging battery materials. It offers an indicator to rank the rate capabilities of different battery materials and suggests two general methods to improve the rate capability: decreasing the geometric sizes or increasing the diffusion coefficients. Based on this FOM, more comprehensive FOMs for quantifying the rate capabilities of battery materials are expected by incorporating other processes (interfacial reaction, migration) into the current diffusion-dominated electrochemical model. Combined with Peukert's empirical law, it may characterize rate capabilities of batteries in the future. National Research Foundation (NRF) Submitted/Accepted version The authors are grateful for funding support from the National Research Foundation of Prime Minister’s Office of Singapore (NRF2015_IIP003_004).

Thermoelectric energy conversion is an all solid-state technology that relies on exceptional semiconductor materials that are generally optimized through sophisticated strategies involving the engineering of defects in their structure. In this review, we summarize the recent advances of defect engineering to improve the thermoelectric (TE) performance and mechanical properties of inorganic materials. First, we introduce the various types of defects categorized by dimensionality, i.e. point defects (vacancies, interstitials, and antisites), dislocations, planar defects (twin boundaries, stacking faults and grain boundaries), and volume defects (precipitation and voids). Next, we discuss the advanced methods for characterizing defects in TE materials. Subsequently, we elaborate on the influences of defect engineering on the electrical and thermal transport properties as well as mechanical performance of TE materials. In the end, we discuss the outlook for the future development of defect engineering to further advance the TE field. Agency for Science, Technology and Research (A*STAR) Submitted/Accepted version TE materials research at NTU is supported by Agency for Science, Technology and Research (A*STAR), Industry Alignment Fund, Pharos ‘‘Hybrid thermoelectric materials for ambient applications’’ Program (Grant No. 1527200019). TE materials research at Northwestern (TJS, YL, ZZL, and MGK) is supported by the U.S Department of Energy, Office of Science and Office of Basic Energy Sciences for funding under award number DE-SC0014520. YZ acknowledges the support from Hubei Provincial Natural Science Foundation of China (Grant No. 2020CFB217).

Electrocatalytic dinitrogen reduction reaction (N2RR) is an emerging route for ammonia synthesis at ambient conditions. Albeit the “π back-donation” process enables N2RR activity on transition metals with empty d-orbitals, given its dilemma in overcoming hydrogen evolution reaction (HER) competition, exploring p-block-element-based catalysts with relatively inferior HER activity is achievable for high selectivity. The challenge lies in designing rational structure to improve N2RR activity. Here, we synergistically integrate oxygen vacancy (VO) with hydroxyl on Bi4O5I2 (VO-Bi4O5I2-OH), which render this p-block-element-based material active to mimic “π back-donation” behavior because of sufficient vacant orbitals. In neutral media, the electrocatalytic N2RR performance of VO-Bi4O5I2-OH in terms of splendid faradic efficiency (32.4%) is superior to most of the prior reports using p-block-element-based catalysts. Our findings show a new strategy toward standout N2RR activity, which holds great potential in exploiting other p-block-element-based electrocatalysts. Ministry of Education (MOE) Accepted version Q.Y. acknowledges the funding support from Singapore MOE AcRF Tier 1 Grant Nos. RG113/15 and 2016-T1-002-065, and Tier 2 under Grant Nos. 2017-T2-2-069 and 2018-T2-01-010. The authors greatly thank the Facility for Analysis, Characterization, Testing and Simulation (FACTS) of Nanyang Technological University, Singapore, for using their TEM, SEM, and XRD equipment.

Aqueous Al-ion batteries (AAIBs) are the subject of great interest due to the inherent safety and high theoretical capacity of aluminum. The high abundancy and easy accessibility of aluminum raw materials further make AAIBs appealing for grid-scale energy storage. However, the passivating oxide film formation and hydrogen side reactions at the aluminum anode as well as limited availability of the cathode lead to low discharge voltage and poor cycling stability. Here, we proposed a new AAIB system consisting of an Al x MnO2 cathode, a zinc substrate-supported Zn-Al alloy anode, and an Al(OTF)3 aqueous electrolyte. Through the in situ electrochemical activation of MnO, the cathode was synthesized to incorporate a two-electron reaction, thus enabling its high theoretical capacity. The anode was realized by a simple deposition process of Al3+ onto Zn foil substrate. The featured alloy interface layer can effectively alleviate the passivation and suppress the dendrite growth, ensuring ultralong-term stable aluminum stripping/plating. The architected cell delivers a record-high discharge voltage plateau near 1.6 V and specific capacity of 460 mAh g-1 for over 80 cycles. This work provides new opportunities for the development of high-performance and low-cost AAIBs for practical applications. National Research Foundation (NRF) Accepted version

We investigate the structural and physical properties of the AgSnmSbSem+2 system with m=1-20 (i.e. SnSe matrix and ~5-50 % AgSbSe2) from length scales ranging from atomic, nano and macro. We find the 50:50 composition, with m=1 (i.e. AgSnSbSe3), forms a stable cation disordered cubic rock-salt p-type semiconductor with a special multipeak electronic valence band structure. AgSnSbSe3 has an intrinsically low lattice thermal conductivity of ~0.47 Wm-1K-1 at 673 K owing to the synergy of cation disorder, phonon anharmonicity, low phonon velocity, and low-frequency optical modes. Fur-thermore, Te alloying on Se sites creates a quinary high entropy NaCl-type solid solution AgSnSbSe3-xTex with randomly disordered cations and anions. The extra point defects and lattice dislocations lead to glass-like lattice thermal conductiv-ities of ~0.32 Wm-1K-1 at 723 K and higher hole carrier concentration than AgSnSbSe3. Concurrently, the Te alloying promotes greater convergence of the multiple valence band maxima in AgSnSbSe1.5Te1.5, the composition with the highest configurational entropy. Facilitated by these favorable modifications, we achieve a high average power factor of ~9.54 μWcm-1K-2 (400-773 K), a peak thermoelectric figure of merit ZT of 1.14 at 723 K and a high average ZT of ~1.0 over a wide temperature range of 400-773 K in AgSnSbSe1.5Te1.5. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Accepted version This work was supported by the Department of Energy, Office of Science Basic Energy Sciences under grant DE-SC0014520, DOE Office of Science (sample preparation, synthesis, XRD, TE measurements, TEM measurements, DFT calculations). YL and QY gratefully acknowledge National Natural Science Founda-tion of China (61728401). This work made use of the EPIC facilities of Northwestern’s NUANCE Center, which has re-ceived support from the Soft and Hybrid Nanotechnology Ex-perimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Re-search Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. User Facilities are supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and DE-AC02-05CH11231. Access to facilities of high performance computational resources at the Northwest-ern University is acknowledged. The authors also acknowledge Singapore MOE AcRF Tier 2 under Grant Nos. 2018-T2-1-010, Singapore A*STAR Pharos Program SERC 1527200022, Singapore A*STAR project A19D9a0096, the support from FACTs of Nanyang Technological University for sample analysis.

Despite the rapid development of perovskite light-emitting diodes (PeLEDs) in recent years, blue PeLEDs’ efficiencies are still inferior to those of their red and green counterparts. The poor performance is associated with, among other factors, halide segregation in bromide-chloride materials and energy funneling to lowest bandgaps in multilayered Ruddlesden–Popper (RP) systems. This study reports that compositional engineering through prudent selection of the A-site cation in a pure bromide RP system can result in a narrow distribution of layered domains. With a narrow distribution centered around the desired RP domain, efficient energy cascade to yield blue emission is ensured. Coupled with rapid nucleation induced by an antisolvent deposition technique, record efficiencies of 2.34 and 5.08%, corresponding to color-stable deep blue (∼465 nm) and cyan (∼493 nm), respectively, were attained. This composition and process engineering to design favorable structural landscape is transferrable to other material systems, which paves the way for high-performance PeLEDs. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

In recent years, the increasing demand for high-capacity and safe energy storage has focused attention on zinc batteries featuring high voltage, high capacity, or both. Despite extensive research progress, achieving high-energy-density zinc batteries remains challenging and requires the synergistic regulation of multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies of high-energy-density zinc batteries and critically analyze the positive effects and potential issues of these strategies in optimizing the electrochemistry, cathode materials, electrolytes, and device architecture. Finally, the challenges and perspectives for the further development of high-energy-density zinc batteries are outlined to guide research towards new-generation batteries for household appliances, low-speed electric vehicles, and large-scale energy storage systems. Ministry of Education (MOE) Submitted/Accepted version This work was supported by the National Natural Science Foundation of China (Grant Nos. 51972346, 51932011), the Hunan Outstanding Youth Talents (2021JJ10064), the Program of Youth Talent Support for Hunan Province (2020RC3011), and the Innovation-Driven Project of Central South University (No. 2020CX024). H.J.F. acknowledges the financial support from the Ministry of Education by a Tier 1 grant (RG157/19).

Rational design of noble metal catalysts with the potential to leverage efficiency is vital for industrial applications. Such an ultimate atom-utilization efficiency can be achieved when all noble metal atoms exclusively contribute to catalysis. Here, we demonstrate the fabrication of a wafer-size amorphous PtSe film on a SiO substate via a low-temperature amorphization strategy, which offers single-atom-layer Pt catalysts with high atom-utilization efficiency (~26 wt%). This amorphous PtSe (1.2 < x < 1.3) behaves as a fully activated surface, accessible to catalytic reactions, and features a nearly 100% current density relative to a pure Pt surface and reliable production of sustained high-flux hydrogen over a 2 inch wafer as a proof-of-concept. Furthermore, an electrolyser is demonstrated to generate a high current density of 1,000 mA cm. Such an amorphization strategy is potentially extendable to other noble metals, including the Pd, Ir, Os, Rh and Ru elements, demonstrating the universality of single-atom-layer catalysts. [Figure not available: see fulltext.], This work was supported by the Singapore National Research Foundation Singapore programme (NRF-CRP21-2018-0007, NRF-CRP22-2019-0060, NRF-CRP18-2017-02 and NRF–CRP19–2017–01) and the Singapore Ministry of Education via AcRF Tier 3 (MOE2018-T3-1-002), AcRF Tier 2 (MOE2017-T2-2-136, MOE2019-T2-2-105 and MOE2018-T2-1-176) and AcRF Tier 1 (RG7/18 and 2019-T1-002-034). It was also supported by the National Key Research and Development Program of China (2019YFA0705400, 2021YFE0194200), the National Natural Science Foundation of China (11772153, 22073048, 21763024, 22175203, 22006023), the Natural Science Foundation of Jiangsu Province (BK20190018), the National Key R&D Program of China (2021YFA1500900), the Fundamental Research Funds for Central Universities (531119200209, NE2018002, NJ2020003) and the High-Performance Computing Center of Nanjing Tech University. Catalan Institute of Nanoscience and Nanotechnology (ICN2) acknowledges funding from Generalitat de Catalunya 2017SGR327 and the project NANOGEN (PID2020-116093RB-C43), funded by MCIN/AEI/10.13039/501100011033/. ICN2 is supported by the Severo Ochoa programme from Spanish MINECO (grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 823717-ESTEEM3.

Layered ternary oxides LiNix Mny Coz O2 are promising cathode candidates for high-energy lithium-ion batteries (LIBs), but they usually suffer from the severe interfacial parasitic reactions at voltages above 4.3 V versus Li+ /Li, which greatly limit their practical capacities. Herein, using LiNi1/3 Mn1/3 Co1/3 O2 (NMC111) as the model system, a novel high-temperature pre-cycling strategy is proposed to realize its stable cycling in 3.0-4.5 V by constructing a robust cathode/electrolyte interphase (CEI). Specifically, performing the first five cycles of NMC111 at 55 °C helps to yield a uniform CEI layer enriched with fluorine-containing species, Li2 CO3 and poly(CO3 ), which greatly suppresses the detrimental side reactions during extended cycling at 25 °C, endowing the cell with a capacity retention of 92.3% at 1C after 300 cycles, far surpassing 62.0% for the control sample without the thermally tailored CEI. This work highlights the critical role of temperature on manipulating the interfacial properties of cathode materials, opening a new avenue for developing high-voltage cathodes for Li-ion batteries. National Research Foundation (NRF) Submitted/Accepted version This work was supported by Singapore National Research Foundation (Nanomaterials for Energy and Water Management CREATE Programme).

GeTe is an excellent mid-temperature thermoelectric material with high dimensionless figure of merit (ZT) values at temperatures over 600 K. Its near-room-temperature performance is less studied due to the intrinsic high carrier concentration. Here, we successfully enhance the Seebeck coefficient of GeTe from ~ 30 to 220 μV·K−1 at 300 K, which is achieved by AgInSe2 alloying and Bi doping. It is demonstrated that Bi doping helps to optimize the Seebeck coefficient without deteriorating the intrinsic electrical transport properties of the matrix. A high room-temperature power factor (PF) of ~ 11 μW·cm−1·K−2 is achieved for a wide range of Bi-doped samples. The simultaneously introduced abundant point defects cause mass and strain fluctuations, which decrease the lattice thermal conductivity (κL) to a low value of 0.6 W·m−1·K−1 at 300 K. Due to the synergetic effects of Bi doping in AgInSe2-alloyed GeTe, a high room-temperature ZT value of 0.46 is obtained together with a high ZT value of 1.1 at 523 K. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version This work was financially supported by the Singapore MOE AcRF Tier 2 (Nos. 2018-T2-1-010), Singapore A*STAR project (A19D9a0096 and SC25/21-102419), Singapore MOE Tier 1 RG128/21. Q. Zhu and A. Suwardi acknowledge Agency for Science, Technology and Research (A*STAR), Singapore Career Development Fund (CDF) (No. C210112022) and the Sustainable Hybrid Lighting System for Controlled Environment Agriculture Program (No. A19D9a0096). Z. Li thanks the support from S&T Program of Hebei (No. 206Z4403G).

Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO2 /Mn2+ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn4 SO4 ·(OH)6 ·xH2 O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Znx MnO(OH)2 nanosheets in which the MnO2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries. Ministry of Education (MOE) Submitted/Accepted version This work was financially supported by the National Natural Science Foundation of China (21972111, 22179109), Natural Science Foundation of Chongqing (cstc2018jcyjAX0714), and Venture & Innovation Support Program for Chongqing Overseas Returnees (cx2019073), Chongqing Engineering Research Center for Micro-Nano Biomedical Materials and Devices, and Chongqing Key Laboratory for Advanced Materials and Technologies. H.J.F. thanks the financial support from Singapore Ministry of Education by Tier 1 grant (RG 85/20).

Strain in layered transition-metal dichalcogenides (TMDs) is a type of effective approach to enhance the catalytic performance by activating their inert basal plane. However, compared with traditional uniaxial strain, the influence of biaxial strain and the TMD layer number on the local electronic configuration remains unexplored. Herein, via a new in situ self-vulcanization strategy, biaxially strained MoS2 nanoshells in the form of a single-crystalline Ni3 S2 @MoS2 core-shell heterostructure are realized, where the MoS2 layer is precisely controlled between the 1 and 5 layers. In particular, an electrode with the bilayer MoS2 nanoshells shows a remarkable hydrogen evolution reaction activity with a small overpotential of 78.1 mV at 10 mA cm-2 , and negligible activity degradation after durability testing. Density functional theory calculations reveal the contribution of the optimized biaxial strain together with the induced sulfur vacancies and identify the origin of superior catalytic sites in these biaxially strained MoS2 nanoshells. This work highlights the importance of the atomic-scale layer number and multiaxial strain in unlocking the potential of 2D TMD electrocatalysts. Ministry of Education (MOE) Submitted/Accepted version This work was supported from the Singapore Ministry of Education by AcRF Tier 1 (RG125/21). The authors acknowledge financial support from the National Science Fund for Distinguished Young Scholars (Grant No. 51825103), the Natural Science Foundation of China (Grant Nos. 52001306, 22005116), and the International Postdoctoral Exchange Fellowship Program (Grant No. 20190067)

The practical application of the Zn-metal anode for aqueous batteries is greatly restricted by catastrophic dendrite growth, intricate hydrogen evolution, and parasitic surface passivation. Herein, a polyanionic hydrogel film is introduced as a protective layer on the Zn anode with the assistance of a silane coupling agent (denoted as Zn-SHn). The hydrogel framework with zincophilic -SO3 - functional groups uniformizes the zinc ions flux and transport. Furthermore, such a hydrogel layer chemically bonded on the Zn surface possesses an anti-catalysis effect, which effectively suppresses both the hydrogen evolution reaction and formation of Zn dendrites. As a result, stable and reversible Zn stripping/plating at various currents and capacities is achieved. A full cell by pairing the Zn-SHn anode with a NaV3 O8 ·1.5 H2 O cathode shows a capacity of around 176 mAh g-1 with a retention around 67% over 4000 cycles at 10 A g-1 . This polyanionic hydrogel film protection strategy paves a new way for future Zn-anode design and safe aqueous batteries construction. Ministry of Education (MOE) Submitted/Accepted version This work was supported from Singapore Ministry of Education by Tier 2 grant (T2EP50121-0012). J.-L.Y. is thankful to the financial support by the China Scholarship Council (No.202006210070).

Harvesting the excess energy from absorbed above bandgap photons is a promising approach to overcome the detailed balance limit for higher solar cell efficiencies. However, this remains very challenging for 2D layered halide perovskites as the fast excess energy loss competes effectively with charge extraction. Herein, the authors engineer the energy cascade manifold of quantum well (QW) states in quasi-2D Ruddlesden–Popper perovskites by facile tuning of the organic spacer to decelerate the energy loss. The resulting excess energy loss rate is up to two orders slower compared to 3D perovskites, thus enabling efficient carrier extraction. 2D electronic spectroscopy reveals further insights into the structural and energetic disorder of these layered systems. Importantly, a judicious choice of the organic spacer holds the key to tailoring the coherent coupling between QWs that strongly influences the competition between the energy cascade and charge extraction. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version The authors acknowledge Dr. Teddy Salim from the Facility for Analysis Characterization Testing and Simulation (FACTS), School of Material Science and Engineering, Nanyang Technological University, for the UPS measurement. This research/project was supported by the Ministry of Education under its AcRF Tier 2 grants (MOE2019-T2-1-006, MOE2019-T2-1-097, and MOE-T2EP50120-0004); and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI-2018-04). E.C. acknowledges the “CQ-TECH” STARS Grant 2019 (2019-UNPD0Z9-0166571). E.F. acknowledges a Ph.D. fellowship from the Department of Excellence program “NExuS.

Aqueous potassium-ion batteries (AKIBs), utilizing fast diffusion kinetics of K+ and abundant electrode resources, are an emerging technology offering high power density and low cost. Many efforts have been made by far to enhance the electrochemical performances of AKIBs, and some encouraging milestones have been achieved. To provide a deep understanding of the progress, challenges, and opportunities of the emerging AKIBs, the recent advances in both cathode and anode materials, and electrolytes of the AKIB systems are comprehensively summarized and discussed. Additionally, the research efforts on the optimization of electrode material properties, the revealing of the reaction mechanism, the design of electrolytes, and the full cell fabrication for AKIBs are highlighted. Finally, insights into opportunities and future directions for achieving high-performance AKIBs and their applications are proposed. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the National Natural Science Foundation of China (51832004, 21905218), the Key Research and Development Program of Hubei Province (2021BAA070), the Natural Science Foundation of Hubei Province (2019CFA001, 2020CFB519), the Sanya Science and Education Innovation Park of Wuhan University of Technology (2021KF0019, 2020KF0019), and the Fundamental Research Funds for the Central Universities (WUT: 2020IVB034, 2020IVA036). This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2019-T2-2-127 and MOE-T2EP50120-0002), A*STAR under AME IRG (A2083c0062), and the Singapore National Research Foundation Competitive Research Program (NRFCRP18-2017-02). This work was supported by A*STAR under its IAF-ICP Programme I2001E0067 and the Schaeffler Hub for Advanced Research at NTU. This work was also supported by NTU-PSL Joint Lab collaboration. X. Z. gratefully acknowledges financial support from the Chinese Scholarship Council.

The development of perovskite photovoltaics has so far been led by solution-based coating techniques, such as spin-coating. However, there has been an increasing interest in thermal evaporation (TE) as an industrially compatible method to fabricate perovskite solar cells (PSCs). TE has several advantages compared to solution processing, including a high degree of process control, excellent film uniformity, low material consumption, conformal substrate coverage, a lack of toxic solvents, and superb device reproducibility and scalability. These benefits make TE an ideal choice to upscale lab-scale PSCs into modules. Here, we discuss three types of TE-based perovskite deposition techniques, namely 1-step TE, multistep all-TE, and multistep hybrid of TE–gas reaction and TE–solution processing. We summarize their fundamental principles and applications, firstly on small-area PSCs and then on modules. Finally, we provide our outlook on important research topics for TE PSCs, namely device interlayers, defect passivation, and device stability. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version The authors wish to thank the National Research Foundation (NRF), Prime Minister’s Office, Singapore under the Solar Competitive Research Program (S18-1176-SCRP) and the Competitive Research Program (NRF-CRP25-2020-0004) for financial support. The authors also acknowledge T.J. Jacobsson and E. Unger’s The Perovskite Database (perovskitedatabase.com), from which a part of the data of devices discussed in this review was taken.

Thermoelectric materials have obtained worldwide attention as they are attractive for waste heat recovery and solid-state cooling. However, their performance is usually sensitive to material compositions, which is less favorable for industrial applications. In this work, we developed composition-insensitive GeTe-based compounds ((100-x-y)%GeTe-x%CuBiSe2-y%PbTe, CBSx-Pby) with high ZTmax as well as ZTave values. The compositional insensitivity can be associated with the persistently high quality factors across the range of compositions. This is largely due to the interplay between electrical and thermal transport caused by the synergy of CuBiSe2 and PbTe alloying. CuBiSe2 alloying can effectively tune the carrier concentrations, while PbTe alloying can significantly decrease the thermal conductivity at a minor sacrifice of electrical properties. The combined effects of CuBiSe2 and PbTe alloying lead to high carrier mobility of 60 cm2V−1s−1 and low thermal conductivities for CBSx-Pby samples simultaneously. Consequently, high ZTave values of 1.4–1.5 in the temperature range of 400 K and 773 K for broad compositions (CBS3-Pby, y = 2 – 8 and CBSx-Pb6, x = 2 – 5) are achieved. A single-leg module is also fabricated, which shows a high power density of 1.46 W/cm2 and an excellent efficiency of 13.4%. The high ZTave with compositional insensitivity and the outstanding module performance demonstrate the promising large-scale application of the developed GeTe-based compositions. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version This study was supported by the Basic Science Center Project of NSFC under Grant No. 51788104, the National Key R&D Program of China No. 2018YFB0703603, the MOE Tier 1 RG128/21 and Singapore A*STAR project A19D9a0096. A. Suwardi acknowledges funding from Agency for Science, Technology and Research (A*STAR), Singapore Career Development Fund (CDF) C210112022.

Electricity-driven water splitting can facilitate the storage of electrical energy in the form of hydrogen gas. As a half-reaction of electricity-driven water splitting, the oxygen evolution reaction (OER) is the major bottleneck due to the sluggish kinetics of this four-electron transfer reaction. Developing low-cost and robust OER catalysts is critical to solving this efficiency problem in water splitting. The catalyst design has to be built based on the fundamental understanding of the OER mechanism and the origin of the reaction overpotential. In this article, we summarize the recent progress in understanding OER mechanisms, which include the conventional adsorbate evolution mechanism (AEM) and lattice-oxygen-mediated mechanism (LOM) from both theoretical and experimental aspects. We start with the discussion on the AEM and its linked scaling relations among various reaction intermediates. The strategies to reduce overpotential based on the AEM and its derived descriptors are then introduced. To further reduce the OER overpotential, it is necessary to break the scaling relation of HOO* and HO* intermediates in conventional AEM to go beyond the activity limitation of the volcano relationship. Strategies such as stabilization of HOO*, proton acceptor functionality, and switching the OER pathway to LOM are discussed. The remaining questions on the OER and related perspectives are also presented at the end. Ministry of Education (MOE) Accepted version This work was supported by the Campus for Research Excellence and Technological Enterprise (CREATE) in Singapore and the Singapore Ministry of Education Tier 2 Grants (MOE2017- T2-1-009 and MOE2018-T2-2-027 (S)).

Energy-harvesting systems generate electricity or produce fuels such as hydrogen from various energy sources such as thermal energy, kinetic energy, and renewable energy. For several decades, many researchers have studied the conversion of such energy for use in applications on various scales, from mega-watt grid systems to the micro-watt internet of things (IoTs). This Special Issue entitled “Highly Efficient Energy Harvesting Based on Nanomaterials” presents seven peer-reviewed journal papers written by outstanding authors worldwide [1,2,3,4,5,6,7]. These novel studies cover various topics related to thermal energy management, kinetic energy harvesting, and electrochemical energy conversion. National Research Foundation (NRF) Published version S.W.L. acknowledges the support from the National Research Foundation, Prime Minister’s Office, Singapore under its NRF-ANR Joint Programme (grant number Award No. NRF2019-NRFANR052 KineHarvest).

The increasing concern on the safety risks associated with the flammable organic electrolytes in alkali-ion batteries and the pursuit of both high energy density and power density in one device has spurred the investigation of aqueous multivalent metal ion hybrid supercapacitors. Zinc ion hybrid supercapacitors (ZIHSCs) have the advantages of low standard potential, high theoretical capacity and good safety in aqueous electrolytes. In this review, the recent advancements achieved in ZIHSCs have been summarized and discussed. The progress in cathode, anode, electrolyte and the approaches adoptable to improve the electrochemical performance of ZIHSCs have been categorized. Mechanism investigation through different ex-situ and in-situ methods, incorporation of multifunctionality and integration are also demonstrated. Adoption of more in-situ characterization methods to understand the electrochemical mechanism of ZIHSCs is encouraged. Future development of ZIHSCs with higher active materials utilization rate and power output for practical applications is envisioned, assembly of ZIHSCs with more functionality is also expected National Research Foundation (NRF) Published version The authors acknowledge the funding support by the National Research Foundation, Prime Minister's Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) program. P.S.L. acknowledges the funding support from the National Research Foundation Investigatorship (NRF-NRFI201605).

Wearable sensors and electronics for health and environment monitoring are mostly powered by batteries or external power supply, which requires frequent charging or bulky connecting wires. Self-powered wearable electronic devices realized by integrating with solar cells are becoming increasingly popular due to their ability to supply continuous and long-term energy to power wearable devices. However, most solar cells are vulnerable to significant power losses with decreasing light intensity in the indoor environment, leading to an errant device operation. Therefore, stable autonomous energy in a reliable and repeatable way without affecting their operation regime is critical to attaining accurate detection behaviors of electronic devices. Herein, we demonstrate, for the first time, a self-powered ion-sensing organic electrochemical transistor (OECT) using carbon electrode-based perovskite solar cells (CPSCs), which exhibits a highly stable device operation and independent of the incident light intensity. The OECTs powered by CPSCs maintained a constant transconductance (gm) of ~60.50±1.44 μS at light intensities ranging from 100 mW cm-2 to 0.13 mW cm-2. Moreover, this self-powered integrated system showed good sodium ion sensitivity of -69.77 mV decade-1, thereby highlighting its potential for use in portable, wearable, and self-powered sensing devices. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) W.L.L. would like to acknowledge funding support from Ministry of Education (MOE) under AcRF Tier 2 grant Nos. (2018-T2-1-075 and 2019- T2-2-106), A*STAR AME IAF-ICP Grant (No. I1801E0030), and National Robotics Programme (W1925d0106).

There has been a huge amount of interest in perovskites recently and new structures of hybrid perovskites are frequently reported. The classification of perovskites has been unambiguous in the discussion of 3D and layered 2D perovskites due to the dimensional constraints. However, in 1D perovskites, the additional degrees of freedom have resulted in a large number of possible structural configurations. The new proposed notation aims to classify these structures based on the connectivity of the octahedra of the perovskite, which has a periodic repeating pattern. However, the notation should be restricted to simple 1D perovskites and haloplumbate structures as the notation would become too cumbersome when applied to an exotic framework which has 3D characteristics, such as perovskite polytypes. National Research Foundation (NRF) Published version The following funding is acknowledged: National Research Foundation Singapore (grant No. NRF-CRP14-2014-03).

Lithium-ion batteries (LIBs) are vital energy-storage devices in modern society. However, the performance and cost are still not satisfactory in terms of energy density, power density, cycle life, safety, etc. To further improve the performance of batteries, traditional “trial-and-error” processes require a vast number of tedious experiments. Computational chemistry and artificial intelligence (AI) can significantly accelerate the research and development of novel battery systems. Herein, a heterogeneous category of AI technology for predicting and discovering battery materials and estimating the state of the battery system is reviewed. Successful examples, the challenges of deploying AI in real-world scenarios, and an integrated framework are analyzed and outlined. The state-of-the-art research about the applications of ML in the property prediction and battery discovery, including electrolyte and electrode materials, are further summarized. Meanwhile, the prediction of battery states is also provided. Finally, various existing challenges and the framework to tackle the challenges on the further development of machine learning for rechargeable LIBs are proposed. Energy Market Authority (EMA) Ministry of Education (MOE) National Research Foundation (NRF) National Supercomputing Centre (NSCC) Singapore Accepted version C.L., X.Z., and L.Z. contributed equally to this work. Q.Y. acknowledges the funding support from Singapore MOE AcRF Tier 1 grant nos. 2020-T1-001-031, and Tier 2 grant nos. 2017-T2-2-069. Y.W. acknowledges the Nation Research Foundation, Prime Minister’s Office, Singapore under its Energy Programme (EP Award No. NRF2017EWT-EP003-023) administrated by the Energy Market Authority of Singapore; its Green Data Centre Research (GDCR Award No. NRF2015ENC-GDCR01001-003) administrated by the Info-communications Media Development Authority. M.S. gratefully acknowledges the financial support from National Research foundation of Singapore Investigatorship Award Number NRFI2017-08 and AStar AME programmatic funding number A20H3g2140. S.L. acknowledges the financial support from the Academic Research Fund Tier 1 (RG8/20), Tier 1 (RG104/18) and the computing resources from National Supercomputing Centre Singapore. The authors also like to acknowledge 111 project (D18023) from Zhengzhou University for their support for this work.

Synthetic nitrogen fertilizer such as urea has been key to increasing crop productivity and feeding a growing population. However, the conventional urea production relies on energy-intensive processes, consuming approximately 2% of annual global energy. Here, we report on a more-sustainable electrocatalytic approach that allows for direct and selective synthesis of urea from nitrate and carbon dioxide with an indium hydroxide catalyst at ambient conditions. Remarkably, Faradaic efficiency, nitrogen selectivity and carbon selectivity reach 53.4%, 82.9% and ~100%, respectively. The engineered surface semiconducting behaviour of the catalyst is found to suppress hydrogen evolution reaction. The key step of C–N coupling initiates through the reaction between *NO2 and *CO2 intermediates owing to the low energy barrier on {100} facets. This work suggests an appealing route of urea production and provides deep insight into the underlying chemistry of C–N coupling reaction that could guide sustainable synthesis of other indispensable chemicals. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Supercomputing Centre (NSCC) Singapore Accepted version Q.Y. acknowledges funding support from Singapore MOE AcRF Tier 1 grant no. 2020-T1-001-031, Tier 2 grant no. 2017-T2-2-069 and Singapore A*STAR project A19D9a0096. G.Y. acknowledges funding support from the US Department of Energy (grant number: DE-SC0019019) and Welch Foundation Award F-1861. S.L. acknowledges financial support from the Academic Research Fund Tier 1 (RG8/20), Tier 1 (RG104/18) and computing resources from the National Supercomputing Centre Singapore. This work is also supported by the Users with Excellence programme of Hefei Science Center of CAS(2020HSC-UE003). We greatly thank the Facility for Analysis, Characterization, Testing and Simulation (FACTS) of Nanyang Technological University, Singapore, for using their TEM, SEM and XRD equipment. We acknowledge NTU Center of High Field NMR Spectroscopy and Imaging. We also thank the National Synchrotron Radiation Laboratory for help in characterizations.

Metal selenides are considered as a group of promising candidates as the anode material for sodium-ion batteries due to their high theoretical capacity. However, the intrinsically low electrical and ionic conductivities as well as huge volume change during the charge-discharge process give rise to an inferior sodium storage capability, which severely hinders their practical application. Herein, we fabricated In2Se3/CoSe2 hollow nanorods composed of In2Se3/CoIn2/CoSe2 by growing cobalt-based zeolitic imidazolate framework ZIF-67 on the surface of indium-based metal-organic framework MIL-68, followed by in situ gaseous selenization. Because of the CoIn2 alloy phase in between In2Se3 and CoSe2, a heterostructure consisting of two alloy/selenide interfaces has been successfully constructed, offering synergistically enhanced electrical conductivity, Na diffusion process, and structural stability, in comparison to the single CoIn2-free interface with only two metal selenides. As expected, this nanoconstruction delivers a high reversible capacity of 297.5 and 205.5 mAh g-1 at 5 and 10 A g-1 after 2000 cycles, respectively, and a superior rate performance of 371.6 mAh g-1 at even 20 A g-1. Ministry of Education (MOE) Accepted version This work was financially supported by Fundamental Research Funds for the Central Universities (ZYGX2019J030). Q.Y. acknowledges the funding support from Singapore MOE AcRF Tier 1 grant no. 2020-T1-001-031.

Electrolyzers coupling electrocatalytic hydrogen evolution with oxidation reactions of small organic molecules have the merits of reducing cell voltage and generating high-value products. Herein, an electrolyzer is designed and optimized that can simultaneously achieve efficient hydrogen generation at the cathode, CO2 absorption by the catholyte, and methanol upgrading to formate at the anode. For these purposes, transition metal phosphides are used as the low-cost catalysts. The unique electrolyzer exhibits a low working voltage of 1.1 V at 10 mA cm-2 . Under optimal conditions, the Faraday efficiencies of hydrogen evolution and formic acid conversion reactions, which are the reaction products at the cathode and anode, respectively, are nearly 100% at various current densities from 10 to 400 mA cm-2 . Meanwhile, the CO2 absorption rate is about twice that of the hydrogen generation rate, which is close to the theoretical value. An innovative and energy-efficient strategy is presented in this work to realize simultaneous hydrogen production and CO2 capture based on low-cost catalyst materials. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Accepted version H.J.F. acknowledges the funding support from the Singapore MOE by Tier 1 (RG157/19, RG85/20) and Agency for Science, Technology, and Research (A*STAR), Singapore by AME Individual Research Grants (A1983c0026).

As the practical capacity of conventional Li‐ion batteries (LIBs) approaches the theoretical limit, which is determined by the rocking‐chair cycling architecture, a new cycling architecture with higher capacity is highly demanded for future development and electronic applications. Here, a deep‐cycling architecture intrinsically with a higher theoretical capacity limit than conventional rocking‐chair cycling architecture is developed, by introducing a follow‐up cycling process to contribute more capacity. The deep‐cycling architecture makes full use of movable ions in both of the electrolyte and electrodes for energy storage, rather than in either the electrolyte or the electrodes. Taking LiMn2O4‐mesocarbon microbeads (MCMB)/Li cells as a proof‐of‐concept, 57.7% more capacity is obtained. Moreover, the capacity retention is as high as 84.4% after 2000 charging/discharging cycles. The deep‐cycling architecture offers opportunities to break the theoretical capacity limit of conventional LIBs and makes high demands for new‐type of cathode materials, which will promote the development of next‐generation energy storage devices. National Research Foundation (NRF) The research leading to these results has received funding from National Research Foundation of Prime Minister's Office of Singapore (proposal ID: NRF2015_IIP003_004 and NRF2015EWT-EIRP002-008) and grants under its Campus of Research Excellence and Technological Enterprise (CREATE) programme

Thermoelectrics enable waste heat recovery, holding promises in relieving energy and environmental crisis. Lillianite materials have been long-term ignored due to low thermoelectric efficiency. Herein we report the discovery of superior thermoelectric performance in Pb7Bi4Se13 based lillianites, with a peak Figure of merit, zT of 1.35 at 800 K and a high average zT of 0.92 (450 - 800 K). A unique quality factor is established to predict and evaluate thermoelectric performances. It considers both band nonparabolicity and band gaps, commonly negligible in conventional quality factors. Such appealing performance is attributed to the convergence of effectively nested conduction bands, providing a high number of valley degeneracy, and a low thermal conductivity, stemming from large lattice anharmonicity, low-frequency localized Einstein modes and the coexistence of high-density moiré fringes and nanoscale defects. This work rekindles the vision that Pb7Bi4Se13 based lillianites are promising candidates for highly efficient thermoelectric energy conversion. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University Published version Q.Y.Y. acknowledges the Singapore MOE Tier 2 under Grant MOE2018-T2-1-010, Singapore A*STAR Pharos Program SERC 1527200022. Q.Y.Y. and J.W.X. acknowledge the Singapore A*STAR project A19D9a0096. This work is also supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI, Grant JP 19F19057. L.H. acknowledges the International Research Fellowship of JSPS. F.Y.Q. acknowledges the Chinese Scholarship Council (CSC) for the scholarship in Tokyo Institute of Technology. X.X.Z. thanks for the support from the Presidential Postdoctoral Fellowship, Nanyang Technological University, Singapore via grant 03INS000973C150. K.H. and D.V.M.R. acknowledge funding from the Accelerated Materials Development for Manufacturing Program at A*STAR via the AME Programmatic Fund by the Agency for Science, Technology and Research under Grant No. A1898b0043.

Layered alkali metal oxides have been emerged as an alternative group with low-cost and promising electrocatalysts in water oxidation. The distinct layered configuration may offer some interesting possibilities to tune the intrinsic activity by regulating the intralayer edge-shared CoO6 octahedra and the CoO2 interlayer spacing/strain. In this work, electrochemical desodiation tuning method is explored on intralayer Ag, Cu, Ce-doped Na0.7CoO2 for highly active OER catalysts. It is demonstrated that the ΔGOH* value in the volcano plot is optimized by proper desodiation. Meanwhile, the lattice strain introduced along with the desodiated process modulates the ΔGOH*, according to first principle calculations. It shows that ~0.157% compressive strain in the CoO2 layers and ~1% tensile strain between CoO2 layers are introduced in the desodiated Ag doped Na0.7CoO2. Among these catalysts, the desodiated Ag-Na0.7CoO2 sample exhibits an optimal RuO2-beyond water oxidation (OER) activity with the lowest overpotential of 236 mV@10 mA/cm2, the smallest Tafel slope of 48 mV/dec and the highest mass current density of 227.8 A/g. This work provides an interesting avenues to optimize existing layered materials with inter/intralayer modifications for highly efficient water oxidation electrolysis. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version This work was supported by National Natural Science Foundation of China (Grant No. 51771144 and 51802252), Singapore MOE AcRF Tier 2 Grant (Nos. 2017-T2-2-069 and 2018-T2-01-010), and National Research Foundation of Singapore (NRF) Investigatorship (NRF2016NRF-NRFI001-22), the Natural Science Foundation of Shaanxi Province (Nos. 2019TD-020, 2020JM-032, 2020JQ-386, 2019JLM-30 and 2017JZ015), Outstanding Youth Project of Shaanxi Province (No. 2021JC-06) and Natural Science Foundation of Jiangsu Province (BK20180237). This research used the resources of the HPCC platform in Xi’an Jiaotong University.

Titanium dioxide (TiO2) electron transport layers (ETLs) are still widely used in perovskite solar cells (PSCs) due to their compatibility with existing printing technologies and favorable energy level alignment for efficient electron extraction. However, TiO2 ETLs suffer from surface defects, e.g. oxygen vacancies, that are detrimental to the perovskite/ETL interface stability, especially under operational conditions. Furthermore, hydroxyl groups present on the TiO2 surface also contribute to deprotonation of acidic organic cations in PSCs. We thus hypothesize that the metal oxide surface turns chemically reactive under 1-sun illumination whereby devices are highly populated with charge carriers and experience elevated temperatures (ca. 60 °C). Here, we introduced facile incorporation of sulfate species on the metal oxide surface to minimize chemical degradation at the perovskite/ETL interface. The sulfate treatment was found to minimally influence the perovskite film morphology grown on top of the ETLs, so ruling out morphological effects and allowing us to study the perovskite/ETL interface stability. We found that the sulfate treated devices exhibited enhanced operational stability under the initial maximum power point voltage (VMPP) over 1800 s of measurement. The sulfate treated devices retained 95% of their initial efficiency while the pristine devices already lost more than 40% of their initial efficiency. We also thermally aged encapsulated perovskite films coated on top of pristine and treated ETLs. We found that the thermally aged perovskite films coated on the pristine ETL contained perovskite hydrate species while the treated samples did not. We thus postulate that the water molecules contributing to hydrate formation were generated solely from the ETL/perovskite interface. Lastly, better energy alignment was also found between the perovskite and sulfate-treated ETL, which also contributes to the improved operational and thermal stability. Ministry of Education (MOE) Submitted/Accepted version This work is supported by Ministry of Education (MOE) under AcRF Tier 2 grant (2019-T2-2-106) and National Robotics Programme (W1925d0106).

The proton exchange membrane (PEM) water electrolysis is one of the most promising hydrogen production techniques. The oxygen evolution reaction (OER) occurring at the anode dominates the overall efficiency. Developing active and robust electrocatalysts for OER in acid is a longstanding challenge for PEM water electrolyzers. Most catalysts show unsatisfied stability under strong acidic and oxidative conditions. Such a stability challenge also leads to difficulties for a better understanding of mechanisms. This review aims to provide the current progress on understandings of OER mechanisms in acid, analyze the promising strategies to enhance both activity and stability, and summarize the state-of-the-art catalysts for OER in acid. First, the prevailing OER mechanisms are reviewed to establish the physicochemical structure-activity relationships for guiding the design of highly efficient OER electrocatalysts in acid with stable performance. We then discuss the reported approaches to improving the activity, from macro-view to micro-view. To analyze the problem of instability, the key factors affecting catalyst stability are summarized and the surface reconstruction is discussed. Various noble-metal based OER catalysts and the current progress of non-noble-metal based catalysts are reviewed. Lastly, the challenges and perspectives for the development of active and robust OER catalysts in acid are discussed. Ministry of Education (MOE) Accepted version

One of the major bottlenecks of perovskite photovoltaic modules fabrication is the homogeneous deposition of perovskite material on large-area substrates. Here, we show that slot-die coating technique combined with synergistic gas quenching and substrate heating can produce compact, homogenous and reproducible Cs0.16FA0.84Pb(I0·88Br0.12)3 perovskite films. We demonstrate the fabrication of perovskite solar cells (PSCs) in a planar (n-i-p) device configuration and attain power conversion efficiency (PCE) of 18% over 0.09 cm2 device active area. The versatility of this crystallization strategy, which eliminates the need for complex solvents or additive engineering, was studied using planar SnO2- and TiO2-coated FTO substrates. Our study provides greater insights into achieving controlled coating and homogeneous crystallization of perovskite films over large-area substrates (~10 × 10 cm2) necessary for the commercialization of this technology. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Submitted/Accepted version This research was supported by NTU start-up grant (M4081866), Ministry of Education (MOE) under AcRF Tier 2 grants (2018-T2-1-075 and 2019-T2-2-106) and National Research Foundation, Prime Minister’s Office, Singapore, under Energy Innovation Research Program (grant numbers: NRF2015EWT-EIRP003-004 and Solar CRP: S18-1176- SCRP). This research was supported by a CEA CTBU funding, under PTC PrintRose project, and by the IDEX Mobility grant from Grenoble Alpes University (Com-UGA).

Excitonic effects underpin the fascinating optoelectronic properties of 2D perovskites that are highly favorable for photovoltaics and light-emitting devices. Analogous to switching in transistors, manipulating these excitonic properties in 2D perovskites using coherent phonons could unlock new applications. Presently, a detailed understanding of this underlying mechanism remains modest. Herein, the origins of the carrier-phonon coupling in 2D perovskites using transient absorption (TA) spectroscopy are explicated. The exciton fine structure is modulated by coherent optical phonons dominated by the vibrational motion of the PbI6 octahedra via deformation potential. Originating from impulsive stimulated Raman scattering, these coherent vibrations manifest as oscillations in the TA spectrum comprising of the generation and detection processes of coherent phonons. This two-step process leads to a unique pump- and probe-energy dependence of the phonon modulation determined by the imaginary part of the refractive index and its derivative, respectively. The phonon frequency and lattice displacement of the inorganic octahedra are highly dependent on the organic cation. This study injects fresh insights into the exciton-phonon coupling of 2D perovskites relevant for emergent optoelectronics development. Ministry of Education (MOE) National Research Foundation (NRF) This research was supported by Nanyang Technological University under its start-up grant (M4080514); the Ministry of Education under its AcRF Tier 1 grant (RG91/19) and Tier 2 grants (MOE2017-T2-2-002, MOE2019-T2-1-006 and MOE2019-T2-1-097); and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI-2018-04). Z.S. gratefully acknowledges Ministry of Education Singapore for the funding of this research through the following grants: AcRF Tier 1 (RG195/17 and RG156/19) and AcRF Tier 3 (MOE2016-T3-1-006 (S)).

Aqueous energy devices are under the spotlight of current research due to their safety, low cost and ease of handling. Metal-organic frameworks (MOFs) and their derivatives have spurred extensive exploration as they provide a library of new electrode materials. The rich and structural flexibilities (such as metal nodes, ligands, pore structure) endow MOFs and MOFs-derivatives with vast opportunities for various energy devices. In this review, we discuss the correlation between MOF structural parameters and electrochemical performance for aqueous energy devices in the scope of zinc-based batteries (Zn-ion, Zn-alkaline and Zn-air batteries), potassium-ion batteries and supercapacitors. For each energy device, the effect of determinative factors and structural modulating strategies of MOFs and derivatives are highlighted. Finally, we summarize the challenges and provide our perspective about MOFs and derivatives for future aqueous energy devices. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Accepted version We thank the financial support from Singapore Ministry of Education by AcRF Tier 2 grant (MOE2017-T2-1-073) and from Agency for Science, Technology, and Research (A*STAR), Singapore by AME Individual Research Grants (A1983c0026), and Guangdong Province Science and Technology Department (Project No. 2020A0505100014).

While aqueous Zn-Na hybrid batteries have garnered widespread attention because of their low cost and high safety, it is still challenging to achieve long cycle-life and stable discharge-voltage due to sluggish reaction kinetics, zinc dendrite formation, and side reactions. Herein, we design a Zn2+/Na+ dual-salt battery, in which sodiation of the NVP cathode favors zinc intercalation under an energy threshold, leading to decoupled redox reactions on the cathode and anode. Systematic investigations of the electrolyte effects show that the ion intercalation mechanism and the kinetics in the mixture of triflate- and acetate-based electrolytes are superior to those in the common acetate-only electrolytes. As a result, we have achieved fast discharging capability, suppressed zinc dendrites, a stable discharge voltage at 1.45 V with small polarization, and nearly 100% Columbic efficiency in the dual-salt mixture electrolyte with optimized concentration of 1 M Zn(OAc)2 + 1 M NaCF3SO3. This work demonstrates the importance of electrolyte regulation in aqueous dual-salt hybrid batteries for the energy storage. Ministry of Education (MOE) Accepted version H. J. Fan acknowledges the support from MOE Tier 1 grant (RG 157/19), and from the China-Singapore International Joint Research Institute (204-A018002).