Boosting Photoelectrochemical Water Oxidation Performance of Nanoporous BiVO4 via Dual Cocatalysts Cobaloxime and Ni-OEC Modification

Bismuth vanadate is an excellent photoanode material for photoelectrocatalytic water oxidation due to the good light absorption and sufficiently positive valence band. However, bare BiVO 4 undergoes poor charge separation and transport and slow kinetics of oxygen evolution reaction. Herein, a dual-cocatalyst-modified photoanode is prepared by depositing Ni-(oxy)hydroxide/borate (Ni-OEC) and molecular cobaloxime on a nanoporous BiVO 4 photoanode. The optimized BiVO 4 photoanode shows an excellent photocurrent density under AM 1.5 G illumination (5.1 mA cm –2 at 1.23 V vs RHE), which is among the highest values using cocatalyst-modified BiVO 4 photoanodes for PEC water oxidation. Furthermore, the maximum surface charge injection efficiency and incident photon-to-current efficiency of the ultimate composite photoanode are 85.6% (at 1.23 V vs RHE) and 83.6%, respectively. These results indicate that surface-modified Ni-OEC and molecular cobaloxime can highly improve the photoelectrocatalytic performance of bare BiVO 4 .