Charge separation at BiVO4/Co3O4 and BiVO4/CoOOH interfaces: Differences between dense and permeable cocatalysts

A CoOOH cocatalyst overlayer is electrochemically deposited on the BiVO 4 surface, and thermal annealing converted CoOOH to Co 3 O 4 in situ. The primary difference between the two cocatalysts lies in their electrolyte permeabilities, resulting in significant differences in their thermodynamic effects on enhancing the photoelectrochemical water oxidation performance. We proved that the CoOOH cocatalyst is unable to achieve true chemical passivation of the surface states of the BiVO 4 photoanode, whereas the Co 3 O 4 cocatalyst can chemically passivate the surface states. Nevertheless, the CoOOH cocatalyst still exhibits better water oxidation performance than Co 3 O 4 , which is attributed to the fact that the permeable CoOOH cocatalyst can accumulate more photogenerated holes in the bulk phase and provide more active sites. However, the CoOOH cocatalyst still exhibits better water oxidation performance compared to Co 3 O 4 , which is attributed to the permeable CoOOH cocatalyst can accumulate more photogenerated holes in its bulk phase and offer more active sites.