Multiscale Design of Array-Type Integrated Electrodes for Gas-Involving Electrocatalytic Reactions

Oxygen evolution/hydrogen evolution/oxygen reduction reactions (OER/HER/ORR) are core processes of electrochemical energy conversion technologies, which are of great significance to sustainable society. With the common gas-involving characteristic, these electrocatalytic reactions are inevitably faced with sluggish intrinsic kinetics at large current conditions, due to difficult mass transfer in multiphase conversion processes. Accordingly, array-type integrated electrodes are regarded as a promising solution, while relevant design strategies are systematically summarized from multiscale perspectives in this review. On one hand, macroscopic multidimensional structural designs are illustrated considering advantages and limitations of various one/two/three-dimensional (1D, 2D, 3D) array units; on the other hand, microscopic chemical/interfacial structural designs are emphasized by various strategies including ionic regulation, vacancy design, phase conversion, and interface engineering, etc. Furthermore, composite strategies are discussed in terms of surface, hierarchical, phase and atomic levels, especially on how to integrate macroscopic structural and microscopic chemical designs simultaneously. Finally, design rules of array-type integrated electrodes as well as outlooks for mass transfer strategies toward gas-involving reactions are provided.