Deciphering engineering principle of three-phase interface for advanced gas-involved electrochemical reactions

As an alternative to conventional energy conversion and storage reactions,gas-involved electrochemical reactions,including the carbon dioxide reduction reaction(CO_(2)RR),nitrogen reduction reaction(NRR)and hydrogen evolution reaction(HER),have become an emerging research direction and have gained increasing attention due to their advantages of environmental friendliness and sustainability.Various studies have been designed to accelerate sluggish kinetics but with limited results.Most of them promote the reaction by modulating the intrinsic properties of the catalyst,ignoring the synergistic effect of the reaction as a whole.Due to the introduction of gas,traditional liquid-solid two-phase reactions are no longer applicable to future research.Since gas-involved electrochemical reactions mostly occur at the junctions of gaseous reactants,liquid electrolytes and solid catalysts,the focus of future research on reaction kinetics should gradually shift to three-phase reaction interfaces.In this review,we briefly introduce the formation and constraints of the three-phase interface and propose three criteria to judge its merit,namely,the active site,mass diffusion and electron mass transfer.Subsequently,a series of modulation methods and relevant works are discussed in detail from the three improvement directions of‘exposing more active sites,promoting mass diffusion and accelerating electron transfer’.Definitively,we provide farsighted insights into the understanding and research of three-phase interfaces in the future and point out the possible development direction of future regulatory methods,hoping that this review can broaden the future applications of the three-phase interface,including but not limited to gas-involved electrochemical reactions.

Integrated electrocatalysts derived from metal organic frameworks for gas-involved reactions

Integrated electrocatalysts(IECs)containing well-defined functional materials directly grown on the current collector have sparked increasing interest in the fields of electrocatalysis owing to efficient activity,high stability and the fact that they are easily assembled into devices.Recently,metal organic frameworks(MOFs)provide a promising platform for constructing advanced IECs because of their properties of low cost,large surface area and efficient structural tunability.In this review,the design principles of state-of-the-art IECs based on MOFs are presented,including by hydrothermal/solvothermal,template-directed,electrospinning,electrodeposition and other methods.The high performance of MOF-derived IECs has also been demonstrated in electrocatalytic gasinvolved reactions.This is promising for green energy storage and conversion.The structure-activity relationship and performance improvement mechanism of IECs are uncovered by discussing some in situ technologies for IECs.Finally,we provide an outlook on the challenges and prospects in this booming field.

Advanced In Situ Characterization Techniques for Direct Observation of Gas-Involved Electrochemical Reactions

Gas-involved electrochemical reactions provide feasible solutions to the worldwide energy crisis and environmental pollution.It has been recognized that various elements of the reaction system,including catalysts,intermediates,and products,will undergo real-time variations during the reaction process,which are of significant meaning to the in-depth understanding of reaction mechanisms,material structure,and active sites.As judicious tools for real-time monitoring of the changes in these complex elements,in situ techniques have been exposed to the spotlight in recent years.This review aims to highlight significant progress of various advanced in situ characterization techniques,such as in situ X-ray based technologies,in situ spectrum technologies,and in situ scanning probe technologies,that enhance our understanding of heterogeneous electrocatalytic carbon dioxide reduction reaction,nitrogen reduction reaction,and hydrogen evolution reaction.We provide a summary of recent advances in the development and applications of these in situ characterization techniques,from the working principle and detection modes to detailed applications in different reactions,along with key questions that need to be addressed.Finally,in view of the unique application and limitation of different in situ characterization techniques,we conclude by putting forward some insights and perspectives on the development direction and emerging combinations in the future.

Rational design of three-phase interfaces for electrocatalysis

Gas-involving electrochemical reactions,like oxygen reduction reaction (ORR),oxygen evolution reaction (OER),and hydrogen evolution reaction (HER),are critical processes for energy-saving,environment-friendly energy conversion and storage technologies which gain increasing attention.The development of according electrocatalysts is key to boost their electrocatalytic performances.Dramatic efforts have been put into the development of advanced electrocatalysts to overcome sluggish kinetics.On the other hand,the electrode interfaces-architecture construction plays an equally important role for practical applications because these imperative electrode reactions generally proceed at triple-phase interfaces of gas,liquid electrolyte,and solid electrocatalyst.A desirable architecture should facilitate the complicate reactions occur at the triple-phase interfaces,which including mass diffusion,surface reaction and electron transfer.In this review,we will summarize some design principles and synthetic strategies for optimizing triple-phase interfaces of gas-involving electrocatalysis systematically,based on the electrode reaction process at the three-phase interfaces.It can be divided into three main optimization directions:exposure of active sites,promotion of mass diffusion and acceleration of electron transfer.Furthermore,we especially highlight several remarkable works with comprehensive optimization about specific energy conversion devices,including metal-air batteries,fuel cells,and water-splitting devices are demonstrated with superb efficiency.In the last section,the perspectives and challenges in the future are proposed.