Synthesis of ternary spinel MCo2O4 (M = Mn, Zn)/BiVO4 photoelectrodes for photolectrochemical water splitting

Bismuth vanadate (BiVO4) as a promising photoelectrode has been received an increasing attention for photoelectrochemical (PEC) water splitting. However, the severe surface charge recombination of BiVO4 still limited the PEC water splitting efficiency. Herein, a simple process is developed for preparing ternary spinel MCo2O4 (M = Mn, Zn) nanoparticles on the surface of BiVO4 photoelectrode as an efficient co-catalyst and constructed p-n junction to suppress the surface charge recombination. The as-prepared best MnCo2O4/BiVO4 and ZnCo2O4/BiVO4 photoelectrodes have exhibited a remarkable photocurrent density of 2.8 mA/cm2 and 2.2 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (RHE) under AM 1.5 G illumination, which is about 3.5 and 2.7 times than the bare BiVO4 photoelectrode, respectively. The deposition of MCo2O4 (M = Mn, Zn) co-catalyst has yielded a large cathodic shift in the onset potential of BiVO4. The PEC studies suggest that the MCo2O4 (M = Mn, Zn) co-catalyst could boost the photogenerated holes transference and enhance the charge separation efficiency in the semiconductor-electrolyte interface. The prominent PEC activity shows that the MCo2O4/BiVO4 photoelectrodes could be used in solar water splitting.