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

Abstract A metal–organic framework (MOF)‐modified bismuth vanadate (BiVO 4 ) 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 BiVO 4 . [Co 2 (bim) 4 ] with small particle size and high dispersion can serve as a promising cocatalyst to accept holes transferred from BiVO 4 and boost surface reaction kinetics for photoelectrochemical (PEC) water oxidation. The photocurrent density of a [Co 2 (bim) 4 ]‐modified BiVO 4 photoanode can achieve 3.1 mA cm −2 under AM 1.5G illumination at 1.23 V versus the reversible hydrogen electrode (RHE), which is better than those of pristine and cobalt‐based inorganic materials‐modified BiVO 4 photoanodes. [Co 2 (bim) 4 ], with porosity and abundant metal sites, exhibits a high surface charge‐separation efficiency (83 % at 1.2 V 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.