Photoelectrochemical technology for solar fuel generation, from single photoelectrodes to unassisted cells: a review

Photoelectrochemical solar fuel generation requires a highly integrated technology for converting solar energy into chemical fuels. Dihydrogen (H2) and carbon-based fuels can be produced by water splitting and CO2 reduction, respectively. Material synthesis, device assembly, and performance of photoelectrochemical systems have rapidly improved in the last decade. More recently, research has shifted from developing single photoelectrodes to fabricating tandem photoelectrochemical cells. Here we review photoelectrochemical systems for solar fuel generation, with focus on photocathodes, photoanodes, protective layers and cocatalysts. We also present strategies for unassisted solar fuel generation.