摘要： Photo-electrochemical (PEC) solar energy conversion offers the promise of low-cost renewable fuel generation from abundant sunlight and water. In this Review, recent developments in photo-electrochemical water splitting are discussed with respect to this promise. State-of-the-art photo-electrochemical device performance is put in context with the current understanding of the necessary requirements for cost-effective solar hydrogen generation (in terms of solar-to-hydrogen conversion efficiency and system durability, in particular). Several important studies of photo-electrochemical hydrogen generation at p-type photocathodes are highlighted, mostly with protection layers (for enhanced durability), but also a few recent examples where protective layers are not needed. Recent work with the widely studied n-type BiVO4 photoanode is detailed, which highlights the needs and necessities for the next big photoanode material yet to be discovered. The emerging new research direction of photo-electrocatalytic upgrading of biomass substrates toward value-added chemicals is then discussed, before closing with a commentary on how research on PEC materials remains a worthwhile endeavor.