Efficient Ion/Electron Transfer of Oxide Photocatalysts for Photochemical and Photoelectrochemical Water Splitting

Abstract

Ion/electron transfer in photochemical (PC) and photoelectrochemical (PEC) devices are critical for determining solar energy conversion efficiency, because the electrochemical reaction occurs at the electrode/electrolyte interface. Herein, we introduce our efforts to improve the ion/electron transfer of oxide photocatalysts in particulate PC systems and PEC water splitting cells. In the first chapter, we discuss about the modification of charge separation and transfer in ternary oxide-based photocatalysts using crystal structure engineering, surface modification, and 2-dimensional anisotropy. However, a single-component material can hardly obtain the characteristics of high electronic conductivity and high catalytic activity in the electrochemical environment simultaneously. Therefore, designing well-arranged hetero-nanostructures that overcome the limitations of different electrochemically active materials and combine the advantages of them is of great significance and still remains a challenge. In the second chapter, we revisit the heteroepitaxial engineering and utilize it into designing 3D hetero-nanostructured electrodes. The lattice mismatch between two different rutile-phase materials induces the heteroepitaxial strain during the initial stage of synthesis, allowing the preferential growth and well-ordered 3D array. Such structural-factor-optimized hetero-nanostructures can satisfy all of the necessary conditions for electrochemical devices, including effective ion diffusion, active facets, large surface area, low interfacial resistance, and high electronic conductivity. Such hierarchical structures demonstrate the superior performance in photoelectrochemical (PEC) conversion.