Atomic vacancies accelerating photochemical solar fuel and value-added chemical production: From materials to mechanism

Abstract

Atomic vacancies in semiconductor materials are usually considered detrimental due to their role in trapping photogenerated carriers, leading to attenuated crystallinity and poor photoelectric conversion efficiency. However, the deliberate and controlled introduction of atomic vacancies within an optimal ratio range in semiconductor photocatalysts can significantly improve their catalytic efficiency. Specifically, vacancy sites can optimize the electronic configuration, promote charge carrier separation, activate reactant molecules, lower activation energies, and improve visible light harvesting, thereby enhancing photocatalytic performance. In this review, we systematically highlight the multiplicity of vacancies in semiconductor materials and examine their innovative role in driving photochemical solar fuel and high-value chemical production. An in-depth discussion of the underlying photoreaction mechanisms associated with the vacancy-mediated process is firstly elaborated, followed by introducing the advanced characterizations employed to uncover the merits of vacancies as well as currently developed strategies for vacancy-engineering in photocatalysts. Next, the current advances in utilizing vacancy contained photocatalysts for photochemical solar fuel and value-added chemical production are discussed and appraised, putting emphasis on their applications in water splitting, CO₂ conversion, H₂O₂ generation, and N₂ fixation. With the opportunities and challenges in this field, we concluded by presenting an outlook on the further prospects and key issues for the practical application of vacancy contained semiconductor materials. We sincerely hope that this review can spur new concepts to advance industrial-scale solar fuel and value-added chemical generation using vacancy-engineered semiconductor photocatalysts.