A Cobalt-Based Metal-Organic Framework as Cocatalyst on BiVO4 Photoanode for Enhanced Photoelectrochemical Water Oxidation

A metal-organic framework (MOF)-modified bismuth vanadate (BiVO4) photoanode is fabricated by an ultrathin sheet-induced growth strategy, where ultrathin cobalt oxide sheets act as a metal source for the in situ synthesis of Co-based MOF poly[Co-2(benzimidazole)(4)] (denoted [Co-2(bim)(4)]) nanoparticles on the surface of BiVO4. [Co-2(bim)(4)] with small particle size and high dispersion can serve as a promising cocatalyst to accept holes transferred from BiVO4 and boost surface reaction kinetics for photoelectrochemical (PEC) water oxidation. The photocurrent density of a [Co-2(bim)(4)]-modified BiVO4 photoanode can achieve 3.1 mAcm(-2) under AM 1.5G illumination at 1.23V versus the reversible hydrogen electrode (RHE), which is better than those of pristine and cobalt-based inorganic materials-modified BiVO4 photoanodes. [Co-2(bim)(4)], with porosity and abundant metal sites, exhibits a high surface charge-separation efficiency (83% at 1.2V versus RHE), leading to the enhanced PEC activity. This work will bring new insight into the development of MOF materials as competent cocatalysts for PEC water splitting applications.