A Cobalt-Based Metal-Organic Framework as Cocatalyst on BiVO 4 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[Co2 (benzimidazole)4 ] (denoted [Co2 (bim)4 ]) nanoparticles on the surface of BiVO4 . [Co2 (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 [Co2 (bim)4 ]-modified BiVO4 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 BiVO4 photoanodes. [Co2 (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.