BiVO ₄ –Cu ₂ O/CuO Nanocubes with High Charge Injection and Charge Separation Rates for Enhanced Photoelectrochemical Water Oxidation

High Resolution Image Download MS PowerPoint Slide Bismuth vanadate (BiVO 4 ) shows promise as a photoanode for water oxidation, with a relatively low band gap of 2.4 eV. However, its performance is limited by poor carrier separation and surface recombination. To address these limitations, a BiVO 4 –Cu 2 O/CuO nanocube (NC) heterojunction was successfully developed, increasing the photogenerated oxygen evolution current density to 2.3 mA/cm 2 at 1.23 V vs RHE, compared to 1.4 mA/cm 2 for bare BiVO 4 . Addition of drop-casted Cu 2 O/CuO NCs on BiVO 4 increases both the charge injection efficiency and the charge separation efficiency to over 60% at 1.23 V vs RHE. In comparison, the addition of drop-casted CuO nanowires (NWs) to BiVO 4 increased the charge injection efficiency to over 65%, but it only moderately increased the charge separation efficiency to 49% at 1.23 V vs RHE. These results highlight the importance of the interface between BiVO 4 and the catalyst layer for an enhanced photocurrent. In the Cu 2 O/CuO NCs, bulk Cu 2 O likely serves as a hole-extracting heterojunction, while surface CuO likely functions as a catalyst. In contrast, the CuO NWs function primarily as a catalyst.