Mo-doped BiVO4 modified with NH2-MIL-88B(Fe) cocatalyst overlayer for enhanced photoelectrochemical water oxidation

[Display omitted] •A Mo:BiVO4@NH2-MIL-88B(Fe) composite photoanode was prepared.•The tight contact between Mo:BiVO4 and Fe-MOF allows for fast charge transfer.•Fe-MOF cocatalyst can accelerate the OER kinetics and promote charge separation.•The Mo:BiVO4@Fe-MOF shows enhanced PEC performance and excellent stability. The photoelectrochemical (PEC) performance of BiVO4 is limited by poor charge separation and slow surface water oxidation kinetics. Herein, an simple and effective caffeic acid-assisted solvothermal method was developed to grow Fe-based metal–organic framework (NH2-MIL-88B(Fe)) overlayer onto the Mo-doped BiVO4 for efficient PEC water oxidation. The synergistic role of Fe-MOF cocatalyst and Mo dopant resulted in a 3.5-fold photocurrent density (1.46 mA cm−2) increase in comparison with bare BiVO4 (0.46 mA cm−2) at 1.23 V [vs. reversible hydrogen electrode (RHE)] and showed an obviously negative shift of the onset potential (200 mV). The enhanced PEC performance can be attributed to the improved charge separation and injection efficiency with Mo doping and Fe-MOF coating, the introduction of Fe-MOF also increased the utilization of visible-light and served as an efficient electrocatalyst to accelerate the oxygen evolution reaction (OER) kinetics. This work provides a universal strategy for constructing semiconductor/MOFs photoanodes for enhanced photoelectrochemical water splitting.