Defect engineering in ceramic photoelectrodes: a multiscale approach to control carriers dynamics in photoelectrochemical water splitting

Ceramic photoanodes offer chemical stability and tunable defect states for photoelectrochemical water splitting, yet their solar-to-hydrogen efficiency typically remains below 5%, significantly below theoretical limits. High carrier recombination and slow surface kinetics are key bottlenecks. This review highlights defect engineering as a critical solution, demonstrating atomic-level control can extend carrier lifetimes by 2-3 orders of magnitude. We innovatively propose a multiscale optimization framework ('Atomic-level defect states → Nanoscale carrier transport → Macroscopic device efficiency') to systematically link defect structures across scales to device performance, overcoming fragmented approaches. Key principles emerge: functionalizing defect types, designing defect density gradients, and aligning defect distributions directionally. This framework bridges material structure with device efficiency and experiment with theory, providing a foundation for designing efficient and stable solar hydrogen systems. Future perspectives emphasize harnessing multiscale defect control to guide rational material design and overcome current efficiency barriers.