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Electrochemical overall water splitting (OWS) with high-efficiency electrocatalysts can directly convert water into hydrogen. This paper demonstrates a commercially applicable way to effectively trigger OWS on a low-cost NiCoP material by trace N doping. Density functional theory (DFT) helps to understand the effect of trace N introduction on the lattice parameters of NiCoP and the Gibbs free energy of H adsorption (ΔGH*). N-NiCoP/NF requires only 119 and 250 mV overpotentials to reach 50 mA cm−2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For OWS, the catalyst exhibits satisfactory activity (52 mA cm−2 with a low voltage of 1.626 V) and long term durability (100 h). In situ UV-vis clarifies that N cooperation accelerates the formation of MOOH species in the OER and the priority of CoOOH formation over NiOOH has been observed in situ for the first time. This study may provide a promising strategy for consideration in designing and optimizing novel electrocatalysts. [ABSTRACT FROM AUTHOR]

The precise detection of trace concentrations of ethylene, a plant hormone gas, is essential for controlling plant health and status. However, owing to the simple chemical structure and low reactivity of ethylene, the highly sensitive and exclusive detection of ethylene has been a significant challenge, despite the strong demand from the agricultural industry. Herein, we report a novel bilayer ethylene gas sensor consisting of a Pd-doped V2O5–TiO2 yolk–shell catalytic overlayer and an In2O3 sensing layer. The coating of 2 wt% Pd-doped V2O5–TiO2 on the In2O3 sensing film remarkably enhances the ethylene response and selectivity over a wide range of operating temperatures (300–400 °C). This is attributed to the reforming of ethylene into more reactive acetaldehyde and the filtering of interference gas into non-reactive forms using the unique Pd–V2O5–TiO2 catalytic overlayer for heterogeneous Wacker oxidation promoted by the yolk–shell sphere structure. To the best of our knowledge, this paper presents the first report on the design of a catalytic overlayer that converts less-reactive ethylene into more-reactive species. The outstanding capability of the unique bilayer sensor proposed in this study enables the monitoring of the ripeness of fruits and correlates well with the results of proton transfer reaction-quadrupole mass spectrometry (PTR-QMS). [ABSTRACT FROM AUTHOR]

Inspired by natural photosynthesis, bio-photoelectrochemical (BPEC) cells based on photo-enzyme coupled catalysis hold great promise for energy conversion and chemical valorization. Here, we report an integrated BPEC system comprising a glucose dehydrogenase (GDH) modified meso-tetrakis(4-carboxyphenyl)-porphyrin/titanium dioxide (TCPP/TiO2) dye-sensitized photoanode and a mesoporous carbon hollow spheres/carbon paper (MCHS/CP) cathode for light-driven glucose oxidation and hydrogen peroxide (H2O2) production, respectively. Such a proposed bifunctional BPEC cell delivers a maximum power output of 0.24 ± 0.03 mW cm−2 with an open circuit voltage of 0.76 ± 0.01 V and achieves efficient H2O2 accumulation (rate: 0.94 ± 0.02 mM cm−2 h−1). Overall, our proof-of-concept assembly leverages the ascendancy of biocatalysis, photoelectrocatalysis, and electrosynthesis to provide an optimized design for biotic/abiotic coupling and expand the functional versatility of green energy devices. [ABSTRACT FROM AUTHOR]

For oxygen conducting materials applied in solid oxide fuel cells and chemical-looping processes, the understanding of the oxygen diffusion mechanism and the materials' crystal structure at different stages of the redox reactions is a key parameter to control their performance. In this paper we report the first ever in situ 3D electron diffraction (ED) experiment in a gas environment and with it uncover the structure evolution of SrFeO2.5 as notably different from that reported from in situ X-ray and in situ neutron powder diffraction studies in gas environments. Using in situ 3D ED on submicron sized single crystals, we observe the transformation under O2 flow of brownmillerite SrFeO2.5 with an intra- and interlayer ordering of the left and right twisted (FeO4)∞ tetrahedral chains (space group Pcmb) into consecutively SrFeO2.75 with space group Cmmm (at 350 °C, 33% O2) and SrFeO3−δ with space group Pm3¯m (at 400 °C, 100% O2). Upon reduction in H2 flow, the crystals return to the brownmillerite structure with intralayer order, but without regaining the interlayer order of the pristine crystals. Therefore, redox cycling of SrFeO2.5 crystals in O2 and H2 introduces stacking faults into the structure, resulting in an I2/m(0βγ)0s symmetry with variable β. [ABSTRACT FROM AUTHOR]

The active layer morphology of non-fullerene organic solar cells is one of the key factors affecting the power conversion efficiency (PCE); however, current experimental techniques cannot be used to directly observe the structural information at the electronic level. Molecular dynamics simulations and quantum chemical calculations provide effective means to explore the morphology and properties of active layers. In this paper, the local molecular stacking of PM6:Y6 films is simulated based on ab initio molecular dynamics (AIMD), and the simulation results show that the donor–acceptor (D–A) molecules are pi–pi stacked and some Y6 molecules are arranged in order. The excited state information of PM6:Y6 dimers was calculated by time-dependent density functional theory (TD-DFT) calculations. The results showed that ΔES1–CT < 0.1 eV, and dimers have very low exciton binding energy (Eb). The charge transfer processes of the D–A dimer are LE → CTX → CS and LE → CTX → CT1 → CS combined with hole–electron analysis. Moreover, ultraviolet-visible (UV-vis) spectra of J-type stacked dimers is similar to that of PM6:Y6 films. Finally, the electron transfer rates (kelectron) and hole transfer rates (khole) were calculated by Marcus theory, and the results showed that the PM6:Y6 system has high charge transfer rates, but the effect of molecular configuration on kelectron is less than that on khole. The properties of PM6:Y6 films were systematically investigated at the theoretical level in this work, and it demonstrated that PM6:Y6 films have pi–pi stacking, low ΔES1–CTX, low Eb, and high charge transfer rates. [ABSTRACT FROM AUTHOR]

In situ producing H2O2via a two-electron oxygen reduction reaction (2e− ORR) pathway offers a promising approach for water purification and environmental remediation. However, it is still challenging to develop an efficient cathode for H2O2 production over a wide pH range. Here, a carbon fiber paper (CFP) self-supported Co–NC cathode (Co–NC/CFP) with adjustable hydrophilicity/hydrophobicity was designed, aimed at improving H2O2 generation and organic wastewater degradation efficiency. It was found that a polytetrafluoroethylene (PTFE)-treated Co–NC/CFP cathode (Co–NC/CFP–PTFE) showed superior H2O2 electrosynthesis performance over a wide pH range, undergoing a 50 h stability test with negligible decay. Combined spectroscopic results and contact angles reveal that the enhanced performance originates from the design of binder-free cathodes and triple-phase boundaries (TPBs), which ensures rapid electron transport and mitigates the H2O2 corrosion process. The integrated cathode fabricated device demonstrates a rapid organic dye degradation efficiency of 99.6% and high reusability. This work provides an avenue not only for designing and fabricating highly efficient free-standing cathodes for H2O2 electrosynthesis but also for improving the reusability of the cathode for sustainable wastewater treatment. [ABSTRACT FROM AUTHOR]

The design of robust electrocatalysts for CO2 electroreduction with large current density and high selectivity for the desired production is a crucial step in realizing a carbon-neutral energy cycle and producing more valuable chemicals and fuels. Herein, the CdCO3/Cd nanostructure was in situ electrodeposited on a carbon paper (CP) substrate to fabricate CdCO3/Cd-CP-x (where x represents the concentration of Cd(NO3)2·4H2O) electrocatalysts that can boost the electrocatalytic performance of CO2 electroreduction. When CdCO3/Cd-CP-2 was applied as an electrocatalyst, the faradaic efficiency (FE) of CO production remained above 90% over a wide potential window, and the current density reached up to 203 mA cm−2 at −2.4 V vs. Ag/Ag+. The enhanced CO2 electroreduction was mainly attributed to the intrinsic properties of the CdCO3/Cd nanostructure with abundant active sites, the introduction of CdCO3, and tight contact with the CP substrate. Density functional theory calculations illustrated that the CdCO3 in the electrocatalyst promoted the formation of the *COOH intermediate, and the synergistic effect between the CdCO3 and the Cd support decreased the adsorption ability for the *CO intermediate, which improved the CO production rate. Furthermore, the CdCO3/Cd-CP-8 electrocatalyst also exhibited highly selective CO production ability at low CO2 concentration with outstanding CO2 conversion rate (34%), which offers a chance to achieve the requirements of practical applications. [ABSTRACT FROM AUTHOR]

Guiding the directional and effective migration of photocarriers is a basic strategy to achieve high performance of catalysts in the photocatalytic water splitting process. In this paper, a new carbon material of graphdiyne (GDY) was prepared by a mechanical ball milling method, and then it was introduced into metal oxide Co3O4 by an ultrasonic in situ stirring method. The lamellar film structure of GDY provides effective support for Co3O4 nanoneedles. It is undeniable that the Co3O4/GDY composite has excellent photocatalytic performance for hydrogen production. The highest hydrogen production activity of Co3O4/GDY-20 is 2456 μmol g−1, which is 7.7 times that of pure Co3O4. In addition, the successful construction of the two-phase S-scheme heterojunction creates favorable conditions for photoelectron migration, and separates the photoelectron–hole pairs successfully. Ultraviolet diffuse reflectance spectra reflect the light absorption capacity of the composite in a wide light wavelength range. Fluorescence spectra and electrochemical detection confirm that photoelectron migration in the composite is effectively regulated, which is very conducive to photocatalytic water splitting. The study shows that the introduction of carbon materials into metal oxides has great potential in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) with high theoretical capacity are a promising candidate of high-energy density rechargeable batteries. However, the practical applications of LMBs were challenged by uncontrolled dendrite growth and the leakage of liquid electrolytes. In this paper, a new kind of quasi-solid polymer electrolyte (QSPE) was designed, which was achieved by in situ polymerizing of 1,3-dioxolane (DOL) with the aid of a multifunctional Mg(OTf)2 additive. Mg(OTf)2 was demonstrated to be not only an efficient catalyst for the polymerization of DOL, but also an effective additive to induce uniform deposition of Li, and the interfacial stability and ionic conductivity were further improved by introducing fluoroethylene carbonate (FEC). As a result, the Mg–PDOL–FEC electrolyte showed a high room-temperature ionic conductivity of 0.5 × 10−3 S cm−1, an electrochemical window of 4.3 V, and a large Li+ transference number of 0.61. Sequentially, the Li–Li symmetric cells based on the Mg–PDOL–FEC electrolyte show no evident polarization enlargement after 1600 h cycling under a current density of 0.5 mA cm−2, and both Li‖Mg–PDOL–FEC‖LiFePO4 and high-voltage Li‖Mg–PDOL–FEC‖LiCoO2-CIE cells exhibit excellent electrochemical performance at room temperature. This work provides an accessible approach to the large-scale application of LMBs with improved safety and prolonged lifetime. [ABSTRACT FROM AUTHOR]

Defect engineering has emerged as a powerful strategy to modulate the surface electronic structure of transitional metal based electrocatalysts, which would tune the adsorption behaviors towards reaction intermediates and thus boost the catalytic activity. In this paper, an array of sulfur vacancy-rich Ni3S2 nanosheets (Vs-Ni3S2) grown in situ on a Ni foam substrate is facilely prepared and employed as a catalytic electrode for electro-oxidation of benzyl alcohol (BA). The defective catalyst has more favorable reaction dynamics with respect to the competitive water oxidation reaction at the anode. A much higher peak current density of 94.2 mA cm−2 and a smaller Tafel slope of 48.15 mV dec−1 are obtained in 1.0 M KOH containing 30 mM BA. Electrolysis results reveal a 100% conversion of BA, 97.8% yield of benzoic acid and ∼100% faradaic efficiency at a relatively low potential (1.325 V vs. RHE), revealing superior energy conversion efficiency. First-principles density functional theory (DFT) results disclose that the availability of sulfur vacancies modulates the electronic conductivity of Vs-Ni3S2 and optimizes the adsorption energy capability towards intermediate products, thus facilitating fast redox reaction kinetics. The work should shed light on the rational design of advanced defective electrocatalysts for biomass valorization. [ABSTRACT FROM AUTHOR]

Ti3C2Tx MXene has a high specific surface area and high conductivity, and can be used in the field of humidity sensing. By controlling the surface termination and microstructure of the material, it is expected to improve the humidity sensing performance of Ti3C2Tx MXene. In this paper, we report a method of electrolytic intercalation treatment of Ti3C2Tx MXene in NaOH solution. Theoretical and experimental results show that this method can remove the original F terminations from the surface of Ti3C2Tx MXene and form a large number of OH and O terminations. The partial oxidation of the surface and the replacement of terminations and the insertion of Na+ lead to the change of the Ti3C2Tx MXene layer morphology from flat to curly and significantly improve the hydrophilicity and resistance. The curly flake structure constructs a fast channel for the entry and exit of water molecules which improves the hydration/dehydration efficiency of the material; the enhanced hydrophilicity of the material sharply reduces the resistance of the material after moisture absorption, which significantly improves the responsiveness of Ti3C2Tx MXene to humidity. The curly flake Ti3C2Tx MXene humidity sensor has an ultra-high sensitivity of S = 1.2 × 105 (two orders of magnitude higher than that of the reported humidity sensor based on MXene), with a fast response rate (2 s), good repeatability and stability (4 weeks), and it can be used for the analysis of human respiration rate, and also for non-contact sensing detection of the human body and environmental humidity detection. [ABSTRACT FROM AUTHOR]

It is urgent to exploit the ability of water–energy co-generation technologies to address the challenges and opportunities for the water–energy nexus. This report presents a cuboid-shaped interfacial solar steam generator made of a selective solar absorber-coated aluminum sheet with filter paper strips attached to its four outer walls as the evaporating surfaces and water-conducting paths for simultaneous freshwater and electricity generation from saltwater (3.5 wt% of NaCl). Connecting all four strips in series, a device with an illumination area of only 1.5 × 1.5 cm2 can generate an open-circuit voltage of 2.7 V with sufficient power to continuously glow an LED during evaporation, without any energy storage devices, in addition to an evaporation efficiency of 88%. For the first time, we could generate sufficient electricity from a single evaporator in a continuous manner to realize practical applications without scaling up, even in the dark. Our device promotes interface solar steam generation as a promising alternative to the solar-driven water–energy nexus. [ABSTRACT FROM AUTHOR]

The performance of bismuth vanadate (BiVO4) photoanodes is limited by surface defects and photo-corrosion instability. This paper proposes a revolutionary protection layer that overcomes these problems. Considering the role of V5+ ion dissolution in photo-corrosion, we propose a surface photoelectrochemical oxidation approach, artificially altering photo-corrosion to advanced photo-oxidation by strategically adding V5+ and H2O2 to the electrolyte. The surface phase transition thus induced creates an unprecedented vanadium oxide (VO2) photoelectrochemical protection layer that is robust, conductive, and ultrathin, while exhibiting atomic controllability. Charge-kinetic characterization of the BiVO4/VO2 photoanodes revealed faster transport of interfacial charges (86%) and transfer of photogenerated carriers through the VO2 protection layer (95%); this approach affords near-ideal performance and contributes toward high stability and extreme durability. The BiVO4/VO2/CoFeOx photoanodes displayed a high photocurrent density of 6.2 mA cm−2 and an onset potential of 0.25 VRHE, with an applied bias photon-to-current efficiency of 2.4% at 0.62 VRHE. [ABSTRACT FROM AUTHOR]

Introducing oxygen vacancies into hydrotalcite-like materials is considered to have positive effects on improving their electrochemical properties. However, there are still huge challenges to fully utilize the effect of exposed surface defects due to the instability in the electron transfer process. Herein, a dual-defect modulated MOF-derived P-Co3O4@NC@Ov-NiMnLDH heterostructure synthesized via the strategy of P doping and vacancy engineering is proposed in this paper, which can take advantage of synergistic defects to realize high-performance features of supercapacitors and avoid the possible deficiencies caused by single defects. A remarkable specific capacity of the optimized electrode at 1 A g−1 is 285.56 mA h g−1. Moreover, the assembled ASC MOF-derived P-Co3O4@NC@Ov-NiMnLDH//CNT@ZIF-8 derived C delivers an excellent specific capacitance of 61.33 mA h g−1 (1 A g−1), a superior capacity retention rate of 91.92% after 12 000 cycles and additionally, an energy density of up to 49.06 W h kg−1 at a power density of 800 W kg−1. The dual-defect modulated electrode can provide new design ideas for superior-performance energy storage materials. [ABSTRACT FROM AUTHOR]

In-plane micro-supercapacitors (MSCs) possess the capabilities of easy integration with planar circuits and feasible flexibility when they are used in flexible and wearable electronics. However, their unsatisfactory energy density limits their wide application. The Zn-ion hybrid supercapacitor is an ideal candidate as it assimilates the high energy-density of the zinc metal anode and high power-density of the pseudocapacitive material cathode. In view of the fact that multiple-metal MXenes could exhibit great potential compared to the single-metal MXenes in energy storage capability, here, Zn//V3CrC3Tx supercapacitors are fabricated. It is found that the partial replacement of Cr atoms for V atoms in V4C3Tx triggers an expansion of layer spacing of the MXene, the adsorption of Zn ions increases, and ion diffusion is promoted, which dramatically improve the capacitance, discharging potential, and cycle stability. Furthermore, in-plane Zn//V3CrC3Tx MSCs on paper demonstrate outstanding electrochemical properties and mechanical flexibility with an ultra-high area energy-density of 51.12 μW h cm−2, long cycle life of 20 000 cycles (84.5% capacitance retention), and outstanding bendability of 10 000 cycles (80.2% capacitance retention). The areal energy density and flexibility outperform most of the reported in-plane flexible MSCs. Owing to the emerging materials design and consummate flexible nature of the scheme, it can inject fresh strength into the development of flexible electronics. [ABSTRACT FROM AUTHOR]

Recently, the application of internet of things devices to semipermanent indoor power systems has garnered significant attention. In this context, organic photovoltaics (OPVs) with unique optoelectronic properties under dim illumination conditions are believed to be particularly suitable for application in indoor energy-harvesting systems. In this paper, an additional PTQ10 homojunction hole transport layer (HTL) is introduced into PTQ10:Y6 OPVs via a simple and effective transfer lamination method. The introduction of the HTL suppresses defect densities drastically and maximizes quasi-Fermi level splitting, leading to a dramatic improvement in indoor performance with the power-conversion efficiency (PCE) increasing by more than 25%. Optimized indoor OPVs equipped with the proposed HTL exhibit an improvement in PCE by 26.5% under a 1000 lx LED and an output power density of 413 μW cm−2 under 1000 lx halogen conditions, both of which are the highest recorded values. This demonstrates the practical viability of operating low-power indoor electron devices using the proposed architecture. [ABSTRACT FROM AUTHOR]

Cu-based ternary chalcogenides have received significant interest as an alternative to conventional photovoltaic materials. CuInS2 and CuInSe2 are the most studied copper-based ternary chalcogenides for photovoltaics. Recently, copper tantalum sulfide (CuTaS3) has been proposed as a potential light absorber for photovoltaics. The synthesis conditions and growth mechanism of ternary systems control the final composition and crystal structure. However, such studies have not been explored for copper tantalum sulfides. Here, we studied the formation and growth mechanism of Cu3TaS4 nanocrystals (NCs) primarily using X-ray diffraction, transmission electron microscopy, and density functional theory (DFT) calculations. The reactions proceed via the formation of cubic Cu2−xS NCs due to soft Lewis acid – soft Lewis base interaction. The Cu2−xS have Cu vacancies, which can be controlled by the relative concentration of the Cu precursor. Ta incorporation occurs in the Cu2−xS NCs at Cu vacancy sites, followed by the diffusion of Ta by replacing Cu into the lattice. Low packing of atoms in Cu3TaS4 provides suitable diffusion channels for Ta and Cu atoms. The diffusion barriers of Ta atoms outweigh that of Cu atoms, implying a reaction rate controlled by Ta diffusion. Thus by varying the relative Cu precursor concentration, the concentration of Cu-vacancies in Cu2−xS can be tuned, which controls the growth rate of Cu3TaS4. Understanding of the growth mechanism obtained in this paper will significantly contribute to the rational synthesis of various Cu-based ternary chalcogenides that is not possible by direct synthesis and hence will have an impact on potential applications in photovoltaics and photocatalysis. [ABSTRACT FROM AUTHOR]

The hydrogels with the LCST (low critical solution temperature) behavior undergo dramatic changes at their transition temperature due to phase separation, such as volume contraction or loss of permeability on warming. Hydrogels with this character have been used extensively in drug delivery, flexible devices, temperature-sensitive robotics, etc. How to regulate the transition behavior of LCST-type hydrogels has been the direction of continuous efforts of researchers. In this paper, a series of changes of PHPA hydrogels that occurred in temperature-sensitive hydrogels were discussed. The results showed that when the temperature increased the hydrogen bond between the polymer and water was broken and the water aggregated into water clusters. The hydrogen bond between water and the polymer and the mobility of the polymer molecular chains played a decisive role in the phase transition of PHPA hydrogels. To modulate the LCST behaviour of the PHPA hydrogels, different concentrations and types of ions, crosslinkers and co-solvents were added to the precursor solution to modify the state of water and the moving ability of the molecular chains. The resulting PHPA hydrogels had a wide LCST range (6–40 °C), adjustable transition rates (0.17–7% s−1) and broad transition windows (2.6–24.6 °C). This modulation method can expand the application of PHPA hydrogels, and also provide a reference for the regulation of other LCST hydrogels. [ABSTRACT FROM AUTHOR]

Wave-transparent lithium aluminosilicate glass-ceramic (LAS) nanofillers are confirmed to be effective in regulating the electromagnetic parameters to satisfy the impedance matching characteristic and enhance the electromagnetic wave loss ability. Herein, a new pitaya slice hierarchical configuration of a 2D LAS/carbon sheet electromagnetic wave absorber was prepared by an effective protocol using an ammonium nitrate-assisted self-polymerization and in situ blown strategy. The obtained 2D pitaya hierarchical configuration exhibited excellent microwave absorption performance with an RL of −55.26 dB and a wide effective absorption bandwidth (≤-10 dB) of 8.21 GHz, covering the whole Ku-band (12–18 GHz) with a low mass adding of only 9.2 wt%. The absorbing mechanism demonstrated that the interfacial polarization, Debye dipolar relaxation, and well-matched characteristic impedance play important roles in improving the microwave absorption properties of the 2D pitaya slice hierarchical configuration. This paper may provide a new route for constructing an effective absorbing network of 2D pitaya slice hierarchical configuration, realizing ultra-low filling and broadband microwave performance. [ABSTRACT FROM AUTHOR]

In this paper, we propose a lightweight wearable thermoelectric (TE) cooler with a rationally designed flexible heatsink. Heatsinks are commonly designed for use with stationary applications, and are consequently rigid and heavy. These traditional heatsinks are incompatible with wearable applications, which must be durable, mechanically flexible, and lightweight while maintaining performance. This paper presents a flexible heatsink based on a ternary composite of silicone elastomer, phase-change material, and graphite powder; this combination is needed to achieve high flexibility and durability as well as the optimum heat capacity and thermal conductivity. Those factors are key requirements for a heatsink to optimize the cooling performance of a TE cooler and maintain a longer cooling capacity. With our optimized ternary composite flexible heatsink, we achieved a cooling temperature of ∼5 K at 0.5 W input power and kept cooling for more than 5 h under ambient conditions. On-body testing of the wearable TE cooler with flexible heatsink was also performed to demonstrate potential applications in the real-world. Our work provides fundamental insights to designing wearable TE devices and paves the way for innovative solutions for on-body thermal management applications such as clothing, hats, seat cushions, and other portable devices. [ABSTRACT FROM AUTHOR]

The three-dimensional self-standing architecture of heteroatom-doped graphene is the ideal electrode material for supercapacitors. However, the facile control of its composition and structure is still a challenge. Herein we have reported a new method of electrochemical-coagulation-type electrophoretic deposition involving a bubble template and subsequent in situ microwave reduction, so as to controllably prepare a sulfur, nitrogen-doped graphene foam (dGF) on ultrathin graphite paper. With the abundant interconnected pores, the high specific surface area of 1806 m2 g−1, and the dual-doping of sulfur and nitrogen, the dGF exhibited a high specific capacitance of 354 F g−1 at 0.5 A g−1 and good rate performance (64.7% capacitance retention at 50 A g−1). By virtue of the advantages of the graphite paper as both the deposition substrate and an in situ microwave reduction initiator, the interdigital electrodes were facilely obtained by tailoring the shape of the graphite paper. The assembled flexible supercapacitor had an energy density of 71.5 W h kg−1 at a power density of 0.65 kW kg−1 and retains a specific capacitance of 99.5% after 10 000 charge–discharge cycles. This study provided an ideal flow process to construct a graphene self-standing architecture, which presents potential application value in catalysis, energy storage, and environmental protection. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous Zn-ion batteries (ZIBs) have obtained extensive attention owing to their high safety, low-cost, environmental friendliness and high energy density. Nevertheless, developing suitable cathode materials remains challenging due to requirements for appropriate microstructure. We present a porous N-doped carbon nanosheet/MnO2 (NCS/MnO2) derived from bacterial cellulose (BC) by a simple route. BC chunks were soaked in urea solution and then carbonized under Ar flow at 900 °C. N-doped carbon nanosheets were obtained and MnO2 was added by reaction with NaMnO4. Benefiting from both the conductivity and porosity of the NCS support, the NCS/MnO2 composite delivers a high capacity and long cycling stability (114 mA h g−1 at 2 A g−1 after 1800 cycles). The electrode reaction mechanism was further investigated and the MnO2 dissolution/deposition mechanism was confirmed, with a critical role of zinc sulfate hydroxide (ZSH) to assist the deposition of MnO2. [ABSTRACT FROM AUTHOR]

Lithium metal anodes could be a key component of high energy density rechargeable batteries, but uncontrolled growth of Li dendrites, large volume expansion, and unstable solid electrolyte interface films seriously hinder the practical applications of Li metal batteries. In this work, a self-standing three-dimensional TiC-modified carbon fibre (TiC@C) network has been fabricated by carbothermal reduction. Binding energy calculations reveal that Li is preferentially plated on TiC rather than the bare C skeleton. The lithiophilic TiC not only serves as a Li nucleation site to assist homogeneous Li deposition, but it also enables rapid Li deposition due to its high electronic conductivity. The 3D conductive structures with high surface area play an important role in reducing the local current density, and also accommodate Li volume changes during repeated cycling. As a result, the TiC@C electrode achieves a nearly zero Li nucleation overpotential and low voltage hysteresis of 150 mV at 2 mA cm−2. Passing 1 mA h cm−2 charge, the coulombic efficiency (CE) was found to be 99.6% over more than 200 cycles. Furthermore, full cells assembled with a LiFePO4 cathode in a conventional carbonate electrolyte achieve an impressive capacity retention of 87% over 250 cycles. This work demonstrates a novel design of a 3D lithiophilic host for dendrite-free lithium metal anodes. [ABSTRACT FROM AUTHOR]

The future demand for large-scale electrochemical energy storage devices has spawned various types of batteries, among which aqueous zinc-ion batteries (ZIBs) have gained much attention due to their safety, affordability, and excellent electrochemical performance. However, some challenges must be urgently addressed before the extensive application of aqueous ZIBs can be realized. Especially, the implementation of zinc anodes faces numerous difficulties, such as the formation of zinc dendrites, passivation of corrosion, and the occurrence of the hydrogen evolution reaction, all of which impede the successful implementation of excellent performance aqueous ZIBs. This paper presents a systematic review of modified Zn substrates in stabilizing zinc anodes. First, the working mechanism of anodes and the challenges of stabilized zinc anodes are briefly summarized. Subsequently, the design principles and recent progress of modified Zn substrates in stabilizing zinc anodes are reviewed. Ultimately, the major prospects and challenges of the future development of modified Zn substrates in stabilizing zinc anodes are proposed. [ABSTRACT FROM AUTHOR]

Taking energy density and safety into account, the anode-free all-solid-state lithium battery is a strong candidate to surpass the capabilities of routine lithium-ion batteries. However, achieving uniform stable lithium metal plating under high areal capacity is a grand challenge facing practical applications of lithium metal batteries. We report a high-performance anode-free all-solid-state lithium battery with a current collector consisting of carbon-reinforced ionic-electronic composites. When an interconnected carbon paper is compounded with a solid electrolyte, a three-dimensional ionic-electronic conduction network can be achieved, affording a large number of sites and scalable spaces for the nucleation and growth of lithium metal. The composite layer can achieve a long cycle life (>5000 cycles), stable lithium metal plating with a high areal capacity (>8 mAh cm−2), which is significantly better than that of the copper current collectors for routine anode-free configurations. The application of high-areal-capacity (4 mAh cm−2) pouch cell provides an efficient and effective strategy for practical anode-free all-solid-state lithium batteries. [ABSTRACT FROM AUTHOR]

Current collectors with light weight, excellent durability, and mechanical robustness are highly demanded for flexible energy storage devices. Here, we prepare free-standing single-walled carbon nanotube films (SWCNFs) with a three-dimensional interconnected porous structure via floating catalyst chemical vapor deposition and apply them as current collectors for flexible supercapacitors. These SWCNFs present high mass loading efficiency, outstanding mechanical robustness, and excellent anti-corrosion properties, showing distinct advantages over conventional metal foil current collectors. The loading efficiency is up to 75% for pseudocapacitive cobalt(II) carbonate hydroxide materials, exhibiting superior electrochemical performance in terms of specific capacitance, rate capability, and cycling performance. In addition, the assembled hybrid supercapacitors (SWCNF-cobalt carbonate hydroxide//SWCNF-polyaniline) exhibit outstanding flexibility under various bending deformations and long-term stability. Free-standing SWCNFs have proven to be promising candidates for ultralight current collectors for flexible supercapacitors. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play important roles in new sustainable energy conversion devices to address the dilemma of energy shortage, but are limited by slow electrochemical kinetic processes. Atomically dispersed catalysts (ADCs) with maximized utilization and well-defined configurations point the way to design efficient and cost-effective multifunctional electrocatalysts. In this paper, we illustrate the relationship between the structure and multifunctional performance of mono-disperse catalysts using reversible oxygen electrocatalysis as an example. Significantly, carbon materials and metal compounds are described as equally important substrate materials. For carbon-based mono-disperse catalysts, the realization of atomic metal sites on carbon supports and the regulation of intrinsic activity are reviewed from the following aspects: molecular design (including substrate design and selection of a center metal atom) and coordination environment. Besides, the substrates of non-carbon-based mono-disperse catalysts are divided into metal oxides, sulfides and carbides/nitrides, and the catalytic mechanism and regulation methods are described. Finally, the prospects and challenges of mono-disperse catalysts for multifunctional electrocatalytic reactions are discussed. [ABSTRACT FROM AUTHOR]

All-inorganic lead halide perovskites have gained a renewed scientific interest due to the outstanding optoelectronic properties unveiled recently, and the related prospects for efficient optical devices. In one of the most recent papers, Svirskas et al. (J. Mater. Chem. A, 2020, 8, 14015) reported on a new phase transition in CsPbBr3. In this comment we show that the claims regarding the new intriguing properties of this material are not supported by convincing experimental data. In particular, a detailed analysis of the results presented in the paper revealed a misinterpretation of the experimental data, as well as substantial inconsistencies between the calorimetric, dielectric, and dilatometric studies. Apparently, this contradicts the existence of a new phase transition in CsPbBr3. We also provide new experimental evidence confirming that the crystal structure is stable below room temperature, at least up to 95 K. [ABSTRACT FROM AUTHOR]

Multifunctional smart hydrogels have been extensively used in wearable devices, soft robotics, tissue engineering, and information storage, especially those with good mechanical properties, desired stimuli-responsiveness, high strain sensitivity, and recyclability. Herein, a novel synergistic dual-network polyurethane hydrogel was prepared through two steps, that is, tannic acid (TA) was firstly incorporated into a polyurethane backbone comprising thermosensitive polyethylene glycol/polypropylene glycol (PEG/PPG) blocks to obtain TA-based polyurethane (TAPU) bearing a phenol–carbamate network; subsequently, TAPU film was immersed in FeCl3 aqueous solution to obtain a TAPU/Fe hydrogel bearing an Fe3+–polyphenol network. The prepared TAPU/Fe hydrogel exhibited a high tensile strength of 0.75 MPa, and large elongation at break of 550%. Benefiting from the thermosensitivity of PEG/PPG blocks and the photothermal effect of the Fe3+/TA complex, the TAPU/Fe hydrogel showed ideal near-infrared (NIR) light triggered actuating behavior and photothermal stability. Under the irradiation of NIR light, the flower-shaped hydrogel actuator can bend upward vertical to the horizontal plane within 2 min. Furthermore, Fe3+ incorporated into the hydrogel matrix can endow the TAPU/Fe hydrogel sensor with high strain sensitivity, which can be used for real-time, stable and repeated monitoring of human movement, and can also be designed as a light-driven switch to light an LED bulb. Built on the reversible cross-linked networks, the TAPU/Fe hydrogel with good biocompatibility can be recycled. Unexpectedly, the TAPU hydrogel showed blue fluorescence under UV light (365 nm) irradiation, and the fluorescence could be quenched (with Cu2+) and recovered (with ethylenediaminetetraacetic acid), resembling rewritable papers. [ABSTRACT FROM AUTHOR]

Lignin-rich black liquor produced from paper-making industries causes severe eco-issues, and how to make full use of it to gain an environmental and economic balance has been gaining increasing attention. Herein, lignin materials from the black liquor are crosslinked and then self-assembled with graphene oxide and bio-based carbon dots by a microwave assisted hydrothermal method to prepare flexible hybrid hydrogels, which could then be employed as electrode materials for manufacturing flexible supercapacitors. This research reveals that for the ternary composite hydrogels, the black liquor lignin effectively inhibits the aggregation of graphene oxide, increases the ordered structure, and introduces sulfur-containing groups for the composites. The incorporation of carbon dots provides electron-rich regions to enhance electrical conductivity and reduce the charge transfer resistance. In addition, the pyridine-N-oxide groups that develop change the surface properties and promote the wettability of the composites. An additive free flexible solid-state symmetrical supercapacitor based on this functionalized hydrogel was fabricated and delivered a capacitance of 94 F g−1 at 0.5 A g−1 using lignin hydrogel electrolyte, and the energy density reaches 13.4 W h kg−1 at a power density of 150 W kg−1. Moreover, the solid-state symmetrical supercapacitor device also exhibits a promising flexible performance, which gives an insight into its potential applications as signal sensors and as portable energy storage. [ABSTRACT FROM AUTHOR]