Defect Engineering in Semiconductor Photocatalysts: Enhancing Photocatalytic Activity for Green Energy Production

Defect engineering is an innovative approach that greatly enhances the performance of photocatalysts, especially in water‐splitting applications for sustainable green energy. This method involves introducing structural imperfections, such as lattice vacancies or foreign atom substitutions, to improve the photocatalytic properties of semiconductors. These defects can alter critical aspects of photocatalytic reactions by adjusting the band structure and increasing light absorption. For instance, anionic vacancies introduce mid‐gap states that broaden light absorption, while cationic vacancies lower the bandgap without forming such states. When both vacancy types are present simultaneously, they create a p–n homojunction, facilitating charge carrier separation through its distinct built‐in electric field. Defects are typically categorized as either surface defects or bulk defects. Surface defects improve charge carrier mobility, promote reactant adsorption, and initiate photocatalytic reactions, while bulk defects frequently serve as recombination centers. In addition, the level of these defects is critical; keeping them at an optimal balance can significantly improve photocatalytic efficiency, but excessive defects may lead to increased recombination, which reduces efficiency. Achieving the right balance in defect type, distribution, and concentration is key to optimizing photocatalytic performance, underscoring the essential role of defect engineering in advancing green energy solutions.