A molecular cobaloxime cocatalyst and ultrathin FeOOH nanolayers co-modified BiVO4 photoanode for efficient photoelectrochemical water oxidation

BiVO4 has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions. So far, sluggish water oxidation kinetics and fast photogenerated charge recombination still hinder the PEC performance of BiVO4. In this study, a novel PEC photoanode was designed by depositing ultrathin FeOOH nanolayers on the surface of nanoporous BiVO4 electrode, followed by modification with a cobaloxime (Co(dmgH)2(4-COOH-py)Cl) molecular cocatalyst. Under irradiation of a 100 mW cm−2 (AM 1.5G) Xe lamp, the photocurrent density of the cobaloxime/FeOOH/BiVO4 composite photoanode reached 5.1 mA cm−2 at 1.23 V vs. RHE in 1.0 M potassium borate buffer solution (pH = 9.0). The onset potential of the optimal cobaloxime/FeOOH/BiVO4 photoanode exhibited a 460 mV cathodic shift relative to bare BiVO4. In addition, the surface charge injection efficiency of the composite photoanode reached ∼80% at 1.23 V vs. RHE and the incident photon-to-current efficiency (IPCE) reached ∼88% at 420 nm.