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A class of monolayer carbon allotropes are proposed. These structures exhibit attractive transport properties such as Van Hove singularity and quasi-one-dimensional metallic wires.

Dissociation barrier of O2* plotted as a function of the surface charge on the PdTe2 bilayer.

Two-dimensional (2D) boron nitride (BN) is a promising candidate for aerospace materials due to its excellent mechanical and thermal stability properties. However, its unusually prominent band gap limits its application prospects. In this work, we report a gapless monolayer BN

Piezo-electrocatalysis based on the non-centrosymmetric materials opens an avenue for mechano-to-H2 production through harvesting mechanical energy, being undergoing significant growth. Direct comparison of the performance of various piezo-electrocatalysts is necessary to obtain the optimal candidates for satisfying the demands of practical application but remains a grand challenge because the acquiescently added sacrificial agents vary considerably in the literature. Herein, we systematically investigate the effect of four commonly used types containing totally 15 sacrificial agents on the piezo-electrocatalytic hydrogen evolution by choosing the typical BaTiO3 catalyst as the demo. It is found that the pH, length of the carbon chain, adsorption strength between catalysts and sacrificial agent, and combination of sacrificial agents would impact on the piezo-electrocatalytic H2 evolution performance. Moreover, the self-decomposition effect is found in the sacrificial agent-water mixtures under ultrasonic vibration, implying that H2 can be generated without piezo-electrocatalysts, which was usually ignored. Thus, in this work, a concept of net H2 yield is suggested to standardize the evaluation of piezo-electrocatalysts in future.

The grain boundary of (DSF)n-graphene is constructed by a double stacking fault. The Dirac cone of (DSF)n-graphene is mainly contributed by the grain boundaries. The surface states prove that (DSF)n-graphene have nontrivial topological features.

The exploration of carbon phases with intact massless Dirac fermions in the presence of defects is critical for practical applications to nanoelectronics. Here, we identify by first-principles calculations that the Dirac cones can exist in graphene with stacking fault (SF) induced periodic line defects. These structures are width (n)-dependent to graphene nanoribbon and are thus termed as (SF)n-graphene. The electronic properties reveal that the semimetallic features with Dirac cones occur in (SF)n-graphene with n = 3m + 1, where m is a positive integer, and then lead to a quasi-one-dimensional conducting channel. Importantly, it is found that the twisted Dirac cone in the (SF)4-graphene is tunable among type-I, type-II, and type-III through a small uniaxial strain. The further stability analysis shows that (SF)n-graphene is thermodynamic stable. Our findings provide an artificial avenue for exploring Dirac Ffermions in carbon-allotropic structures in the presence of defects.

While inheriting the exceptional merits of single atom catalysts, diatomic site catalysts (DASCs) utilize two adjacent atomic metal species for their complementary functionalities and synergistic actions. Herein, a DASC consisting of nickel-iron hetero-diatomic pairs anchored on nitrogen-doped graphene is synthesized. It exhibits extraordinary electrocatalytic activities and stability for both CO2 reduction reaction (CO2RR) and oxygen evolution reaction (OER). Furthermore, the rechargeable Zn-CO2 battery equipped with such bifunctional catalyst shows high Faradaic efficiency and outstanding rechargeability. The in-depth experimental and theoretical analyses reveal the orbital coupling between the catalytic iron center and the adjacent nickel atom, which leads to alteration in orbital energy level, unique electronic states, higher oxidation state of iron, and weakened binding strength to the reaction intermediates, thus boosted CO2RR and OER performance. This work provides critical insights to rational design, working mechanism, and application of hetero-DASCs., Diatomic site catalysts utilize two adjacent atomic metal species for their complementary functionalities and synergistic actions. Here, the authors report the orbital coupling of hetero-diatomic nickel-iron site boosts CO2 reduction reaction and oxygen evolution reaction.

The single-metal atoms coordinating with the surface atoms of the support constitute the active centers of as-prepared single-atom catalysts (SACs). However, under hash electrochemical conditions, (1) supports' surfaces may experience structural change, which turn to be distinct from those at ambient conditions; (2) during catalysis, the dynamic responses of a single atom to the attack of reaction intermediates likely change the coordination environment of a single atom. These factors could alter the performance of SACs. Herein, we investigate these issues using Mo2C(100)-supported single transition-metal (TM) atoms as model SACs toward catalyzing the oxygen reduction reaction (ORR). It is found that the Mo2C(100) surface is oxidized under ORR turnover conditions, resulting in significantly weakened bonding between single TM atoms and the Mo2C(100) surface (TM@Mo2C(100)_O* term for SAC). While the intermediate in 2 e- ORR does not change the local structures of the active centers in these SACs, the O* intermediate emerging in 4 e- ORR can damage Rh@ and Cu@Mo2C(100)_O*. Furthermore, on the basis of these findings, we propose Pt@Mo2C(100)_O* as a qualified ORR catalyst, which exhibits extraordinary 4 e- ORR activity with an overpotential of only 0.33 V, surpassing the state-of-the-art Pt(111), and thus being identified as a promising alternative to the commercial Pt/C catalyst.

Electrocatalytic (EC) and photoelectrocatalytic (PEC) water splitting are effective processes for mass production of hydrogen; however, they usually endure large overpotentials or low conversion efficiency. Therefore, the exploration of efficient and scale-up feasible electrocatalysts and cocatalysts is highly desirable. The novel and emerging single Pt atom catalyst is promising to perfectly satisfy the strict requirements of the EC and PEC hydrogen evolution reaction (HER). Herein, a partial nitridation modification strategy is proposed to anchor single platinum (Pt) atoms through the coordination of lone pair electrons of nitrogen atoms with the unoccupied d orbital electrons of Pt atoms. The fixed single Pt atoms are located on a porous nickel framework on nickel foam (Pt1/N–Ni/NF), and show excellent EC activity with a low overpotential of 33 mV at −10 mA cm−2 for the HER in neutral solution, which is superior to that of the bench-mark commercial electrocatalyst. In addition, the Pt1/N–Ni has been integrated into a Cu2O nanowire photocathode as a cocatalyst, and presents a high photocurrent density of −11.9 mA cm−2 at 0 V vs. RHE and PEC conversion efficiency of 1.75%. The rational design and preparation of a single atom catalyst both as an electrocatalyst for EC and a cocatalyst for PEC water splitting opens up a new avenue for boosting EC and PEC water splitting performance.

Catalytic decomposition of hydrazine monohydrate (N2H4·H2O) represents a promising hydrogen storage/production technology. Nowadays, the development of N2H4 decomposition catalysts is sluggish due primarily to a lack of universal screening rules. Herein, with the aid of first-principles calculations, we identify a reliable descriptor, N2H4 adsorption energy, to properly address N2H4 decomposition kinetics on TM catalysts. Particularly, we extract linear scaling relations between the adsorption energetics of key intermediates, H (and N2H3) vs. NH2 that exert a fundamental limitation on the H2 selectivity of N2H4 decomposition over elementary transition metal catalysts. We propose that catalysts with optimum H2 selectivity may be achieved by independently stabilizing and destabilizing adsorption of H (or N2H3, or both) and NH2, respectively. The disclosed dissociation behaviors of N2H4 and their physical origins are expected to advance the rational design of advanced catalysts for selectively promoting H2 production from N2H4.

The emerging two-dimensional tellurene has been demonstrated to be a promising candidate for photoelectronic devices. However, there is a lack of comprehensive insight into the effects of vacancies and common adsorbates (i.e., O2 and H2O) in ambient conditions, which play a crucial role in semiconducting devices. In this work, with the aid of first-principles calculations, we demonstrate that H2O and O2 molecules behave qualitatively differently on tellurene, while water adsorption can be remarkably promoted by adjacent preadsorbed O2. Upon the formation of Te vacancies, the adsorption of both O2 and H2O molecules is enhanced. More importantly, the existence of H2O and Te vacancies can dramatically facilitate the dissociation of O2, suggesting that tellurene may be readily oxidized in humid conditions. In addition, it is found that the electronic properties of tellurene are well preserved upon either H2O or O2 adsorption on the surface. In sharp contrast, vacancies enable significant modification on the band structure. Specifically, an indirect-to-direct band gap transition is found at a vacancy concentration of 5.3%.

In this study, FeOx and CoOx thin films were successively and uniformly coated on high-surface-area carbon nanotubes by plasma-enhanced atomic layer deposition, which formed a heterojunction of the two oxides. As an electrocatalyst in the oxygen evolution reaction (OER), CoOx/FeOx/CNTs showed excellent electrocatalytic performance in terms of catalytic activity and stability. The overpotential of CoOx/FeOx/CNTs in OER was only 308 mV at 10 mA cm−2, which was lower than those of the pure oxides: CoOx/CNTs (392 mV) and FeOx/CNTs (406 mV). The as-prepared electrocatalyst also displayed better stability than the reference RuO2 material, with almost no attenuation of current density in contrast to the 10% loss seen with RuO2. The OER performance of CoOx/FeOx/CNTs was superior to those of its oxide components due to the formation of heterojunction, which led to a smoother reaction path and a lower overpotential for OER compared to pure oxides, as supported by the density-functional theory (DFT) calculations. These results provide a new direction for the preparation of electrocatalysts for metal–air batteries and water splitting reactions.

The separation efficiency and recombination rate of photogenerated electron–hole pairs play a vital role in photocatalytic activity. We report the incorporation of ultra-small subnano TiOx clusters as outstanding cocatalysts on the surface of plasmonic Ag/AgCl to boost the simulated sunlight photoreactivity. The formed structure is in favour of an efficient photoinduced electron–hole transfer process and suppressing the recombination rate, yielding an enhanced photocatalytic activity. The experimental results show that TiOx@Ag/AgCl exhibits an extraordinarily high activity in the photodegradation of tetracycline (TC) under simulated sunlight irradiation, which is about 21.7 times higher than that of bare Ag/AgCl. Their corresponding apparent quantum efficiency (AQE) is up to 0.917% at 435 nm and 17.459% at 350 nm during the photodegradation of TC, respectively. Moreover, TiOx@Ag/AgCl shows an outstanding long-term stability without obvious performance loss even after ten cycles of photodegradation. The possible enhancement mechanism of the reaction rate is proposed based on the compositional, structural, and optical property analysis. We found that h+ was the major reactive species in the photodegradation process of TC. Our findings on ultra-small TiOx cocatalysts would shed light on the design and development of highly efficient oxide cluster cocatalysts.

Identifying the nature of active centers and structure–performance correlations is of fundamental importance for the successful design of more energy-efficient and/or selective catalysts. Recently, the studies of metal-free catalysts containing sp2- or sp3-hybridized B sites have displayed an attractive prospect for N2 reduction but have obscured the nature of the optimal active B species. Herein, with the aid of first-principles calculations, we explicitly disclose that sp2-hybridized B is the optimal species for providing high activity for N2 reduction and particularly outstanding capability to suppress the competing hydrogen evolution reaction. Specifically, the system with B substituting an edge N atom in the cavity of C2N is proposed to be highly promising for N2 reduction under mild conditions. The developed comprehensive insight is of clear significance for the rational design of advanced catalysts for NH3 synthesis under mild conditions.

The valley-polarized quantum anomalous Hall (VQAH) state, which forwards a strategy for combining valleytronics and spintronics with nontrivial topology, attracts intensive interest in condensed-matter physics. So far, the explored VQAH states have still been limited to magnetic systems. Here, using the low-energy effective model and Floquet theorem, we propose a different mechanism to realize the Floquet VQAH state in nonmagnetic heterobilayers under light irradiation. We then realize this proposal via first-principles calculations in transition metal dichalcogenide heterobilayers, which initially possess the time-reversal invariant valley quantum spin Hall (VQSH) state. By irradiating circularly polarized light, the time-reversal invariant VQSH state can evolve into the VQAH state, behaving as an optically switchable topological spin-valley filter. These findings not only offer a rational scheme to realize the VQAH state without magnetic orders, but also pave a fascinating path for designing topological spintronic and valleytronic devices., 6 pages, 4 figures, Supplemental Material

Currently, development of metal sulfide anodes for sodium-ion batteries (SIBs) with high capacity, fast charging/discharging, and good cycling performance continues to present a great challenge. He...

The exploration of novel two-dimensional semimetallic materials is always an attractive topic. We propose a series of two-dimensional silicon carbides with a tetragonal lattice. The band structure of silicon carbides with tetragonal carbon rings and silicon rings exhibits Dirac cones. Interestingly, the Dirac cone of tetragonal SiC originates from a “ring coupling” mechanism. This mechanism refers to the mutual coupling between the four carbon atoms in the tetragonal C ring, and the same coupling in the tetragonal Si ring. Additionally, the “ring coupling” mechanism is applicable to other group IV binary compounds such as monolayer GeC and SnC. This work provides reliable evidence for the argument that two-dimensional tetragonal materials can produce Dirac cones.

Developing earth-abundant transition metal (TM)-based electrocatalysts toward oxygen reduction reaction (ORR) is significant in overcoming the high cost of fuel cells. Herein, using an as-synthesized proton-conductive coordination polymer (termed TM-DHBQ) as a template, we investigate the ORR performance of a series of such TM-DHBQs via screening 3d, 4d, and 5d TMs. We find that most 3d TM-DHBQs exhibit distinguished durability under ORR turnover conditions. The formation energies of these TM-DHBQs and adsorption free energies of ORR intermediates show a good correlation with the number of outer electrons of TM ions in TM-DHBQs, enabling the formation energy as a robust ORR activity descriptor. The Sabatier-type volcano plot and microkinetic modeling coidentify Fe- and Co-DHBQs as two promising alternatives to Pt-based ORR electrocatalysts. For those TM-DHBQs showing strong bonding to oxygen species, the ORR intermediate is found to combine with the TM ion serving as the active center.

High-valence cobalt sites are considered as highly active centers for the oxygen evolution reaction (OER) and their corresponding construction is thus of primary importance in the pursuit of outstanding performance. Herein, we report the design and facile synthesis of abundant high-valence cobalt sites by introducing Zn2+ into CoFe Prussian blue analogues (PBAs). The modification results in the drastic morphological transformation from a pure phase (CoFe-PBA) to a three-phase composite (CoFeZn-PBA), with a significant increase not only the amount of highly oxidized Co sites but the specific surface area (by up to 4 times). Moreover, the obtained sample also exhibits outstanding electric conductivity. Consequently, an excellent OER performance with an overpotential of 343 mV@10 mA cm-2 and a Tafel slope of 75 mV dec-1 was achieved in CoFeZn-PBA, which outperforms the commercial IrO2 catalyst. Further analysis reveals that CoFeZn-PBA becomes (oxyhydr)oxides after the OER.

Efficient catalysts for hydrogen evolution reactions (HERs) in acid media usually lose substantial performance in alkaline media primarily due to their inefficiency in the prior step: water dissoci...

Rechargeable Zn–air battery is a promising alternative to the widely used lithium–ion battery. Its practical use, however, is hindered by low power density, unsatisfactory energy efficiency, poor durability, and unstable voltage output. Here, we demonstrate a bifunctional catalyst for oxygen evolution and oxygen reduction reactions based on 3D MXene coupled with nitrogen-doped cobalt selenide nanocrystals (N-CoSe2/3D Ti3C2Tx). Combining experimental characterizations and density functional theory (DFT), the excellent performance is ascribed to enhanced intrinsic activity of CoSe2 due to electron transfer from MXene, N doping which lowers the reaction energy barriers, and 3D MXene architecture which provides large specific surface area, high porosity, and good conductivity. Moreover, Zn–air battery equipped with the developed N-CoSe2/3D MXene as the air cathode exhibits better power/energy densities and long-lasting cycling life (over 500 cycles) compared with that of mixed Pt/C and RuO2.

Rechargeable zinc-ion batteries (ZIBs) appear to be a promising candidate for large-scale energy storage system because of the abundance and inherent safety of the zinc negative electrode. Despite these benefits, huge polarization caused by the intercalation of multivalent charge carrier Zn2+ into the cathodic hosts remains a long-standing challenge impeding the development of high-performance ZIBs. Herein, we demonstrate the viability of the V2O5 nanorods constructed 3D porous architectures (3D-NRAs-V2O5) as cathode for ZIBs. Notably, the 3D-NRAs-V2O5 can be scaled up to kilo-gram production based on a simple sol-gel reaction followed by an annealing process. The synergic contributions from the 3D porous framework and layered structures of the 3D-NRAs-V2O5 lead a more facile Zn2+ ions (de)intercalation storage process. Consequently, it offers high reversible capacity of 336 mAh g−1 at a high current density of 50 mA g−1 and exhibits excellent long-term cyclic stability with a capacity retention of 85% over 5000 cycles at a high current density of 10 A g−1. Furthermore, the use of various ex-situ characterization techniques and first-principles calculations has successfully unravelled the Zn2+ ions storage mechanism of the 3D-NRAs-V2O5. Besides the excellent electrochemical performance of the 3D-NRAs-V2O5, it can also be easily scaled up based on the simple synthetic protocol, which shows great potential to be practically used for the next-generation large-scale energy storage applications.

The rhenium-based transition metal dichalcogenides (TMDs), as new members in the TMDs family, have raised great interests recently. Due to the anisotropic structure and unique photoelectric properties, they have potential applications for electrochemical energy conversion and storage. In this work, we performed density functional theory (DFT) calculations on pristine 1T′-ReSe2 toward hydrogen evolution reaction (HER). The results indicated that the Gibbs free energy of the 1T′-ReSe2 edge site for HER could be as small as 0.01 eV, superior to other reported TMDs. Experimentally, we developed a strategy to fabricate sub-5 nm sized 1T′-ReSe2 nanoflakes on carbon nanotubes. Such a small size for the nanoflakes brought abundant edge exposure, which boosted the catalytic activity in the HER. Specifically, the 1T′-ReSe2 nanoflakes needed only 23 and 60 mV overpotentials to achieve −1 and −10 mA cm−2 current densities, along with a low Tafel slope of 37 mV dec−1 and a high exchange current density of 0.3 mA cm−2. The edge-rich and layered 1T′-ReSe2 was also explored as an anode for sodium ion battery. The in operando X-ray absorption near edge structure (XANES) technique was applied to investigate the TMD behavior in real-time during the sodiation/desodiation process. The in situ results revealed that the nanosized 1T′-ReSe2 is electrchemically reversible during discharge/charge cycles. The electrochemical test results demonstrated that 1T′-ReSe2 could be a promising anode material for alkaline batteries.

In this paper, van der Waals heterostructures consisting of MX2 (M = Zr, Hf and X = S, Se) monolayers are modeled. The favorable stacking and stability of the modeled monolayer heterostructures are confirmed through binding energy and phonon dispersion calculations. After confirming stability, the electronic and thermoelectric properties of these compounds are explored using the first-principles calculations combined with semiclassical Boltzmann transport theory. It is found that type-II band alignment in ZrS2 HfSe2 facilitates charge separation for optoelectronics and solar energy conversion. All studied heterostructures show remarkably higher electrical conductivity than corresponding monolayers, responsible for large power factor values, especially at 1200 K. These findings indicate that the creation of van der Waals heterostructures from MX2 may be promising for efficient optoelectronic and thermoelectric devices.

Synthesis of high-performance and cost-effective electrocatalysts towards hydrazine electrooxidation is vital to develop the direct hydrazine fuel cell (DHFC) as a viable energy conversion technology. Herein, we report a combined experimental and theoretical study of nickel phosphides (NixP) as promising catalysts for hydrazine electrooxidation. NixP nanowire array supported on a Ni foam (NF) was synthesized by a one-step phosphorization method using hypophosphite as a P-source. Ni12P5 and Ni2P phases are observed as the products of the direct phosphorization of commercial NF under the applied conditions with Ni2P nanoparticles exclusively distributing on the surface of Ni12P5. The NixP/NF catalyst exhibits a synergetic capabilities of exceptionally high activity, excellent durability and nearly 100% selectivity towards the complete electrooxidation of hydrazine in alkaline condition, which is among the best performance reported on hydrazine electrooxidation catalysts. First-principles calculations have been conducted to gain insight into the catalytic mechanism of Ni phosphides towards hydrazine electrooxidation.

Interfacial interactions between TiO2 nanocrystals and the surrounding environmental media play a critical role in dictating their environmental behaviors. Here two specific-faceted TiO2 crystals, {101} facet and {001} facet, were adopted to investigate facet-mediated aggregation kinetics in aquatic environments. In pristine electrolyte solution (NaCl and CaCl2), {001} TiO2 exhibited higher stability than {101} TiO2 due to the abundant –OH groups on the {001} facet surface. The presence of Suwannee river humic acid (SRHA) significantly improved the stability of TiO2 nanocrystals in a facet dependent manner, in which {101} TiO2 exhibited a more remarkable improvement in stability than {001} TiO2. At a high SRHA concentration (10 mg L−1), both faceted TiO2 displayed comparable stability. The adsorption experiments and attenuated total reflectance Fourier transformation infrared spectroscopy demonstrated that {101} TiO2 induced more pronounced adsorption of SRHA molecules than {001} TiO2, probably driven by the efficient bidentate coordination of –COO– groups in SRHA on the {101} facet. This facet-affected colloidal stability behavior would deepen our understanding on nanomaterial transport and exposure in natural waters.

The development of advanced electrocatalysts for ambient NH3 production is increasingly attractive but severely plagued by low activity and poor selectivity. Herein, we reported first-principles results to explore the potential of transition metal (Sc– Cu, Mo, Ru, Rh, Pd, Re, Ir and Pt) atoms embedded in monolayer g-C3N4 as efficient single-atom electrocatalysts for NH3 production. We found that embedding single Pt atoms in g-C3N4 enables robust stability and good electrical conductivity and particularly results in excellent activity (with a low limiting potential of −0.24 V) at room temperature. Furthermore, the dominant N2 adsorption over that of H atoms suggests superior NH3 selectivity. Mechanistic analyses disclosed that single Pt atoms and g-C3N4 work in concert to address the significant deviation from the nitrogen linear scaling relationships, synergistically providing highly active sites for ambient electrochemical NH3 synthesis.

To gain fundamental understanding of how catalyst composition and structure affects catalytic reaction chemistry is of paramount importance in the search of high-performance electrocatalysts for practical applications. Herein, we report an in-depth study of Ni–Mo–O derived electrocatalysts, a promising but less well investigated electrocatalytic material for the HER, with a focus on the correlation of phase/microstructure and HER activity. A series of Ni foam-supported Ni–Mo–O derived electrocatalysts were prepared using a simple hydrothermal method, followed by annealing treatment under a H2 atmosphere. Depending upon the annealing temperature, different Ni–Mo alloys were formed and the resulting Ni–Mo/MoO3−x nanocomposites exhibited varied HER activities under alkaline conditions following the order of Ni10Mo/MoO3−x > Ni4Mo/MoO3−x > Ni3Mo/Ni4Mo/MoO3−x. A combination of phase/structure/chemical state analyses and first-principles calculations were conducted to gain insight into the variation of apparent catalytic activity. Our study found that the variation of HER activity under alkaline conditions should stem from the intrinsic activity change, which was associated with the change of the amount of MoO3 sites and the variation of Had–alloy binding strength.

Synthesis of high-performance and cost-effective catalysts towards the hydrogen evolution reaction (HER) is critical in developing electrochemical water-splitting as a viable energy conversion technique. For non-precious metal Co- and Ni-based catalysts, hydroxides were found to form on the surface of the catalysts under alkaline environments and benefit the catalytic performance, whereas there is limited systematic study on the explicit influence of hydroxides on the electrocatalytic mechanism and performance of these catalysts. Herein, we report a close correlation observed between the amount of the surface hydroxides formed and the resulting electrocatalytic performance of a Co-Mo-O nanocatalyst through careful comprehensive structural and property characterizations. We found that an appropriate amount of hydroxide can be moderated by simply coating the catalyst surface with carbon shells to optimize the catalytic properties. As a result, a carbon-coated Co-Mo-O nanocatalyst was successfully developed and is among the best reported non-precious HER catalysts with a superior electrocatalytic activity and outstanding durability for the HER under alkaline environment. First-principles calculations were further conducted to probe the nature of the active sites and the role of hydroxides in the Co-Mo-O@C/NF catalyst towards the HER.

Photocatalytic carbon dioxide (CO2) reduction is a sustainable and energy-consumption-free route to directly convert the greenhouse gas into chemicals. Given the vast amount of greenhouse gases, numerous efforts have been devoted to developing inorganic photocatalysts due to their stable, low-cost and environmental-friendly properties. However, more efficient titanium dioxide (TiO2) without noble metal or sacrifice/organic agent is highly desirable for CO2 reduction practical application, and it is also difficult and urgently in demand for TiO2 producing selectively valuable compounds, i.e. industrial chemicals and fuels. Here, we develop a novel “adatom at step” strategy via anchoring single tungsten atom oxide (STAO) site on intrinsic steps of classic TiO2 nanoparticles. The composition of single-sites can be controlled by tuning the ratio of adatom W5+ to neighboring Ti3+, resulting in significant CO2 reduction efficiency and selectively yield of carbon monoxide (CO) or methane (CH4) as main products. The W5+-dominated catalysts can achieve an ultrahigh photocatalytic CH4 production of 59.3 μmol/g/h, while the Ti3+-dominated catalysts can achieve a CO production of 181.4 μmol/g/h, which both exceed those of pristine TiO2 by more than one order of magnitude. The mechanism relies on the accurate control of atomic sites with high coverage and the subsequent excellent electron-hole separation along with favorable adsorption-desorption of intermediates on sites. This approach not only provides a novel strategy for inorganic catalytic single-sites with superior performance, but also identifies the rational design mechanisms of the efficient site with controllable production.

Optimization of solid electrolytes (SEs) is of great significance for lithium-based solid state batteries (SSBs). However, insufficient Li ion transport, deficient interfacial compatibility and formation of lithium dendrites lead to poor cycling performance. Based on Li+ conductive metal-organic frameworks (LCMOFs), herein a multiscale optimization strategy is put forward to facilitate Li+ transport within the MOFs (molecular scale), between the MOFs' boundaries (nanoscale) and across the SE/electrode interface (microscale) in SSBs. LCMOFs are obtained by binding Li+ onto ionogenic chemical groups (-CO2H, -SO3H and -OH) in nanoscale dispersed MOFs. Both experimental results and DFT simulations confirm the key role of ionogenic groups for Li+ transport. Furthermore, benefiting from the optimized interfaces between LCMOF crystals, SEs with excellent electrochemical properties are obtained, including a high ionic conductivity of 1.06 × 10-3 S cm-1 at 25 °C, a wide electrochemical window from 2.0 to 4.5 V, low interfacial resistances and stable Li plating/stripping. The fabricated Li|SE|LiFePO4 SSB exhibits high and stable charge/discharge capacities under wide operation temperatures ranging from -20 to 60 °C.

Highlights 3D flower-like architecture assembled by NH4V4O10 nanobelts (3D-NVO) was fabricated.The Zn2+ ion was intercalated into NVO cathode within the interlayer region (NH4V4O10 ↔ ZnxNH4V4O10).The 3D-NVO cathode could deliver a large reversible capacity of 485 mAh g−1 at a current density of 100 mA g−1 for zinc-ion battery. Electronic supplementary material The online version of this article (10.1007/s40820-020-0401-y) contains supplementary material, which is available to authorized users., Given the advantages of being abundant in resources, environmental benign and highly safe, rechargeable zinc-ion batteries (ZIBs) enter the global spotlight for their potential utilization in large-scale energy storage. Despite their preliminary success, zinc-ion storage that is able to deliver capacity > 400 mAh g−1 remains a great challenge. Here, we demonstrate the viability of NH4V4O10 (NVO) as high-capacity cathode that breaks through the bottleneck of ZIBs in limited capacity. The first-principles calculations reveal that layered NVO is a good host to provide fast Zn2+ ions diffusion channel along its [010] direction in the interlayer space. On the other hand, to further enhance Zn2+ ion intercalation kinetics and long-term cycling stability, a three-dimensional (3D) flower-like architecture that is self-assembled by NVO nanobelts (3D-NVO) is rationally designed and fabricated through a microwave-assisted hydrothermal method. As a result, such 3D-NVO cathode possesses high capacity (485 mAh g−1) and superior long-term cycling performance (3000 times) at 10 A g−1 (~ 50 s to full discharge/charge). Additionally, based on the excellent 3D-NVO cathode, a quasi-solid-state ZIB with capacity of 378 mAh g−1 is developed. Electronic supplementary material The online version of this article (10.1007/s40820-020-0401-y) contains supplementary material, which is available to authorized users.

Understanding on the photogenerated charge separation from a microscopic level remains a challenge and is highly desirable as it provides a cornerstone for designing high-performance photocatalysts. Herein, facet engineering is chosen as a tool to reveal the relationship between the charge separation/transfer and crystal structure. A series of BiOBr nanosheets with dominantly exposed facets of (001) or (010) as well as different lateral facet exposure ratios are constructed via adjusting pH value during the hydrothermal process. It is found that exposure of anisotropic crystal facets allows the separative transfer of photogenerated electrons and holes onto the lateral facet and dominantly exposed facets, respectively, which is attributed to the junction formed between distinct facets (i.e., facet junction). In the case of BiOBr-5 with (010)/(102) facet junction, the electron transfer rate (kET) and efficiency (ηET) are 3.658 × 106 s-1 and 54.09%, which are superior than the counterpart of BiOBr-1 with (001)/(110) facet junction. The fast electron transfer rate and high transfer efficiency of BiOBr-5 result in the high CO evolution rate from CO2 photoreduction under artificial sunlight. Our work may bring some new insights into the mechanism understanding of facet junction and rational design of photocatalysts with high performance for solar energy storage in future.

Quantitatively simultaneous detection of hydroquinone (HQ) and catechol (CC) with low limit of detection (LOD) and wide detection range is of critical significance in water quality control but faces great challenges due to their isomer similarity and a large range of contamination concentrations. Herein, high density of boron atoms is introduced into nitrogen-doped nanocarbon (BNC) to realize simultaneous detection of HQ and CC with a large separation of peak potential (ΔEp) of 111 mV between oxidations of HQ and CC by differential pulse voltammetry. Besides, extremely low LODs of 33.3 and 16.3 nM for HQ and CC were achieved through amperometric I-t curve with wide linear ranges of 0.099 ∼ 43340 µM and 0.049 ∼ 5110 µM, respectively. The systematical investigation of the enhancement mechanism by spectroscopy and DFT calculations clearly reveal that the boron-nitrogen co-doping creates rich electroactive sites for high sensing performance toward HQ and CC, thereby shedding lights on the great effect of a unique nanostructure on electrocatalysis in sensing applications.

Currently, development of metal sulfide anodes for sodium-ion batteries (SIBs) with high capacity, fast charging/discharging, and good cycling performance continues to present a great challenge. Hence, a topochemical conversion strategy is reported to fabricate 2D ultrathin GeS

Interface engineering in heterogeneous catalysis is fascinating because of the modulation of charge-transfer processes and catalytic activity. Herein, by constructing Fe(III)–TiO2 systems with diff...