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

Abstract

The sluggish surface reaction kinetic is the bottleneck limiting the photoelectrochemical (PEC) water oxidation of BiVO4 photoanode, especially for the porous structured BiVO4 with high surface area. Here, Co-based metal–organic frameworks (MOFs) were modified on porous BiVO4 photoanode followed by calcining in the N2 atmosphere, forming BiVO4-MOF-N2 photoanode. The MOF-derived heterostructural cocatalysts significantly enhanced the photocurrent density of BiVO4-MOF-N2, reaching 2.32 mA·cm−2 (1.23 V vs RHE), about 1.15 times that of BiVO4-MOF and 2.64 times that of pristine BiVO4. The comparative study of BiVO4-MOF-N2, BiVO4-MOF, and pristine BiVO4 photoanodes suggested that the Co-MOF-derived heterostructural cocatalyst had a much stronger effect on promoting the surface reactions than pure MOF. The BiVO4-MOF-N2 photoanode had the highest charge transfer efficiency of 63.1 % at 1.3 V vs RHE and the lowest charge transfer resistivity compared with BiVO4 and BiVO4-MOF. Both Co-active centers and conductive carbon matrix contributed to the enhanced charge transfer of BiVO4-MOF-N2 photoanode. A MOF-loading-time dependent PEC performance of BiVO4 photoanode also indicated that the intermediate charge transfer process from BiVO4 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.