Defective Metal–Organic Framework Assisted with Nitrogen Doping Enhances the Photoelectrochemical Performance of BiVO₄

Abstract

BiVO4 is a promising n-type semiconductor for photoelectrochemical (PEC) water splitting, which can serve as a photoanode. However, severe surface recombination and slow water oxidation kinetics hinder the realization of its highly theoretical PEC performance. Single-atom catalyst-like metal–organic frameworks (MOFs) and their derived metal oxides have been broadly investigated to enhance the kinetics of BiVO4 photoanodes. According to the principle of catalysis, only coordinatively unsaturated atoms can participate in the catalytic reaction. Herein, a defective cobalt-based MOF (d-CoMOF) with missing linker defects is modified onto the surface of N-doped BiVO4 (N:BVO) photoanodes. The photocurrent density of d-CoMOF/N:BVO is 3.59 times higher than that of pristine BVO (0.56 mA/cm2) at 1.23 VRHE. The onset potential of d-CoMOF/N:BVO shows a cathodic shift of 300 mV relative to BVO. The roles of the d-CoMOF overlayer and N doping are experimentally revealed. The d-CoMOF modification and N doping could increase the electron density, passivate the surface states, and promote the catalysis kinetics of BVO. Thus, the kinetic parameters, such as the charge separation/injection efficiency, onset potential, and photocurrent density, are significantly enhanced. This work provides a way to use MOFs for PEC water splitting by the introduction of defects.