Chemical Origin and Transport Limits of Current Multiplication in BiVO4 Photoanodes

Current multiplication, where more than one electron transfer per photon absorbed, has the potential to transform photoelectrochemical solar fuel generation. Yet it remains rarely realized, largely because the underlying chemical pathways enabling this process are poorly understood and key bottlenecks are still unidentified. Here on BiVO4 photoanode, we reveal direct evidence of vanadium-mediated current-multiplication pathway. During glycerol oxidation, reactive intermediates spontaneously inject electrons directly into the BiVO4 conduction band through surface V5+ reduction, thereby enabling single-photon–driven multiple-electron transfer. More importantly, we identify that poor electron transport—independent of classical hole–electron separation—as a critical bottleneck limiting current multiplication. Mo doping significantly enhances electron transport and promotes efficient extraction of the injected electrons, thereby unlocking the current-multiplication potential of BiVO4.