Engineering Fe‑N_(4)Electronic Structure with Adjacent Co‑N_(2)C_(2)and Co Nanoclusters on Carbon Nanotubes for Efficient Oxygen Electrocatalysis

Regulating the local configuration of atomically dispersed transition-metal atom catalysts is the key to oxygen electrocatalysis performance enhancement.Unlike the previously reported singleatom or dual-atom configurations,we designed a new type of binary-atom catalyst,through engineering Fe-N_(4)electronic structure with adjacent Co-N_(2)C_(2)and nitrogen-coordinated Co nanoclusters,as oxygen electrocatalysts.The resultant optimized electronic structure of the Fe-N_(4)active center favors the binding capability of intermediates and enhances oxygen reduction reaction(ORR)activity in both alkaline and acid conditions.In addition,anchoring M-N-C atomic sites on highly graphitized carbon supports guarantees of efficient charge-and mass-transports,and escorts the high bifunctional catalytic activity of the entire catalyst.Further,through the combination of electrochemical studies and in-situ X-ray absorption spectroscopy analyses,the ORR degradation mechanisms under highly oxidative conditions during oxygen evolution reaction processes were revealed.This work developed a new binary-atom catalyst and systematically investigates the effect of highly oxidative environments on ORR electrochemical behavior.It demonstrates the strategy for facilitating oxygen electrocatalytic activity and stability of the atomically dispersed M-N-C catalysts.

Photothermal‐boosted polaron transport in Fe_(2)O_(3)photoanodes for efficient photoelectrochemical water splitting

Introduction of the photothermal effect into transition-metal oxide photoanodes has been proven to be an effective method to improve the photoelectrochemical(PEC)water-splitting performance.However,the precise role of the photothermal effect on the PEC performance of photoanodes is still not well understood.Herein,spinel-structured ZnFe_(2)O_(4)nanoparticles are deposited on the surface of hematite(Fe_(2)O_(3)),and the ZnFe_(2)O_(4)/Fe_(2)O_(3)photoanode achieves a high photocurrent density of 3.17 mA cm^(-2)at 1.23 V versus a reversible hydrogen electrode(VRHE)due to the photothermal effect of ZnFe_(2)O_(4).Considering that the hopping of electron small polarons induced by oxygen vacancies is thermally activated,we clarify that the main reason for the enhanced PEC performance via the photothermal effect is the promoted mobility of electron small polarons that are bound to positively charged oxygen vacancies.Under the synergistic effect of oxygen vacancies and the photothermal effect,the electron conductivity and PEC performance are significantly improved,which provide fundamental insights into the impact of the photothermal effect on the PEC performance of small polaron-type semiconductor photoanodes.

Designing Advanced Aqueous Zinc-Ion Batteries:Principles,Strategies,and Perspectives

Aqueous zinc-ion batteries(AZIBs)are an appealing battery system due to their low cost,intrinsic safety,and environmental-friendliness,while their application is plagued by the obstacles from the cathode,electrolyte,and zinc anode.Summarizing the design principles and strategies toward the optimization of cathode,electrolyte,and zinc anode is crucial for the development of AZIBs.Herein,we present a comprehensive analysis of the design principles and promising strategies toward the improvement of AZIBs.Firstly,the various reaction mechanisms are summarized and the existing issues associated with the cathode,electrolyte,and zinc anode are discussed to guide the rational design of AZIBs.Subsequently,we provide an in-depth and comprehensive discussion on the design principles and strategies for the electrodes/electrolyte/separator optimization,and analyze the advantages and disadvantages of various strategies.Importantly,the design principles and strategies of the newly appeared conversion-type AZIBs,such as Zn-S battery and Zn-Se battery,are also discussed and analyzed.The effect of design strategies on the electrochemical performance and the relationship between the current issues and strategies are also unveiled in detail.Finally,some research trends and perspectives are provided for designing better AZIBs.

Emerging Carbonyl Polymers as Sustainable Electrode Materials for Lithium-Free Metal-Ion Batteries

Lithium-ion batteries using inorganic electrode materials have been long demonstrated as the most promising power supplies for portable electronics,electric vehicles,and smart grids.However,the increasing cost and descending availability of lithium resources in combination with the limited electrochemical performance and eco-sustainability have created serious concerns with the competitiveness of lithium-ion batteries.There is a pressing need for the discovery of new redox chemistries between the alternative host materials and charge carriers.Organic nonlithium batteries using organic electrodes have recently attracted considerable interests as the future substitutes for energy storage systems,because of their combined merits(e.g.,natural abundance,rich chemistry of organics,rapid kinetics,and multielectron redox)of Li-free batteries and organic electrodes.Herein,an overview on the state-of-the-art developments of emerging carbonyl polymers for nonlithium metal-ion batteries is comprehensively presented with a primary focus on polyquinones and polyimides from the perspective of chain engineering.Six distinct categories,including monovalent(Na^(+),K^(+)) and multivalent(Mg^(2+),Zn^(2+),Ca^(2+),Al^(3+)) metal-ions batteries are individually outlined.Advantages of polymer electrode materials and characteristics of charge storage mechanisms are highlighted.Some key performance parameters such as specific capacity,rate capability,and cycle stability are carefully discussed.Moreover,aqueous nonlithium batteries based on carbonyl polymers are specially scrutinized due to the less reactivity of Li-free metals when exposed in aqueous electrolytes and ambient atmosphere.Current challenges and future prospects of developing polymer-based batteries are proposed finally.This review provides a fundamental guidance for the future advancement of next-generation sustainable batteries beyond lithium-ion batteries.

Electrochemically Active Phosphotungstic Acid Assisted Prevention of Graphene Restacking for High-Capacitance Supercapacitors

Direct reduction of graphene oxide usually leads to the agglomeration of the as-generated graphene sheets,thus suppressing the surface exposed for energy storage.Herein,graphene oxide was reduced by a one-pot hydrothermal process in the presence of an electrochemically active phosphotungstic acid to produce three-dimensional porous phosphotungstic acid/reduced graphene oxide composites.Phosphotungstic acid molecules were found to be uniformly anchored on the surface of reduced graphene oxide sheets through the electrostatic interaction to prevent the reduced graphene oxide sheets from restacking.

Control on self-assembly structures of rod-coil-rod (PANI)_(98) -(PEG)_(136) -(PANI)_(98) triblock copolymer

The self-assembly behaviors of the rod-coil-rod(PANI)_(98)-(PEG)_(136)-(PANI)_(98) triblock copolymer are investigated in different solvents,such as N-methyl-2-pyrrolidone(NMP),dimethyl formamide(DMF),ethanol and water.The effects of solvents,concentration and ultrasonic irradiation on self-assembly are discussed.The results indicate that the triblock copolymer forms particles,rods,fiber,networks and fiber bands in the above solvents,respectively.Especially,the triblock copolymer can form a multi-layer,tri-dimensional fibrous network and a petaline structure from the mono-layer fibrous network with the increase of its concentration in ethanol.Also,the ultrasonic irradiation has a great effect on the self-assembly of the triblock copolymer.