Promoting photoelectrochemical water oxidation of BiVO4 photoanode via Co-MOF-derived heterostructural cocatalyst

The sluggish surface reaction kinetic is the bottleneck limiting the photoelectrochemical (PEC) water oxidation of BiVO 4 photoanode, especially for the porous structured BiVO 4 with high surface area. Here, Co-based metal–organic frameworks (MOFs) were modified on porous BiVO 4 photoanode followed by calcining in the N 2 atmosphere, forming BiVO 4 -MOF-N 2 photoanode. The MOF-derived heterostructural cocatalysts significantly enhanced the photocurrent density of BiVO 4 -MOF-N 2 , reaching 2.32 mA·cm −2 (1.23 V vs RHE), about 1.15 times that of BiVO 4 -MOF and 2.64 times that of pristine BiVO 4 . The comparative study of BiVO 4 -MOF-N 2 , BiVO 4 -MOF, and pristine BiVO 4 photoanodes suggested that the Co-MOF-derived heterostructural cocatalyst had a much stronger effect on promoting the surface reactions than pure MOF. The BiVO 4 -MOF-N 2 photoanode had the highest charge transfer efficiency of 63.1 % at 1.3 V vs RHE and the lowest charge transfer resistivity compared with BiVO 4 and BiVO 4 -MOF. Both Co-active centers and conductive carbon matrix contributed to the enhanced charge transfer of BiVO 4 -MOF-N 2 photoanode. A MOF-loading-time dependent PEC performance of BiVO 4 photoanode also indicated that the intermediate charge transfer process from BiVO 4 to active centers strongly affected the final charge transfer and PEC performances. This work provides new insights into the design of high-performance photoelectrochemical electrodes based on heterostructural cocatalysts.