Chemical Origin and Transport Limits of Current Multiplication in BiVO ₄ Photoanodes for Glycerol Oxidation

Current multiplication, where more than one electron transfer per photon is 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 the BiVO 4 photoanode, we reveal direct evidence of vanadium-mediated current-multiplication pathway. During glycerol oxidation, reactive intermediates spontaneously inject electrons directly into the BiVO 4 conduction band through surface V 5+ reduction, thereby enabling single-photon-driven multiple-electron transfer. More importantly, we identify 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 BiVO 4 .