A closed-loop strategy for optimizing metal-oxide-semiconductor photoanodes towards boosted photoelectrochemical hydrogen production

Photoelectrochemical (PEC) hydrogen generation using metal oxide semiconductors (MOS) is a promising carbon-neutral strategy due to MOS's low cost, stability, and non-toxicity. However, limited PEC performance enhancement, caused by poor mechanistic understanding of charge carrier dynamics, impedes practical commercialization. This review presents recent MOS photoanode advances, emphasizing the interrelationship between fabrication, surface/interface engineering, and PEC evaluation (FSI-PEC). By integrating advanced characterization techniques and theory (ACTT), we provide microscopic insights into charge carrier generation - transport - injection (C-GTI) mechanisms and identify key material limitations. We propose a unified FSI-PEC/ACTT closed-loop strategy that establishes interrelationships between conventional chemical and physical approaches, enabling rational MOS optimization and accelerated discovery of new compositions. By correlating macroscopic PEC performance with microscopic charge carrier dynamics, this approach identifies performance bottlenecks and provides feedback for optimal materials. Future directions to overcome the limited PEC performance enhancement for practical PEC hydrogen production are outlined, providing an interdisciplinary roadmap.