A BiVO4 film photoanode with re-annealing treatment and 2D thin Ti3C2TX flakes decoration for enhanced photoelectrochemical water oxidation

Bismuth vanadate (BiVO 4 ) has been envisioned as a promising photoanode material for photoelectrochemical (PEC) water oxidation. However, the PEC performance of BiVO 4 based photoanodes is usually dragged down by the poor charge transport and slow kinetics for an oxygen evolution reaction (OER). Here, a novel composite photoanode of Ti 3 C 2 T X /BiVO 4 was fabricated for the first time by spin coating thin Ti 3 C 2 T X (MXene) flakes onto the surface of a BiVO 4 film grown on the FTO substrate. A facile re-annealing treatment of bare BiVO 4 /FTO photoanode in argon can impressively boost the photocurrent density from 2.1 mA cm −2 up to 2.95 mA cm −2 . Experimentally, we clearly elucidated that by re-annealing, the interfacial (BiVO 4 /FTO) charge recombination could be effectively suppressed due to the better contact between the BiVO 4 film and FTO. The coating of thin Ti 3 C 2 T X flakes onto the BiVO 4 film would further increase the photocurrent density to 3.45 mA cm −2 (measured at 1.23 V vs. reversible hydrogen electrode (RHE) under 1 sun illumination), exhibiting a photoconversion efficiency of 0.78% and a surface charge separation efficiency of 73%. The outstanding PEC performance can be mainly ascribed to the coating of the thin Ti 3 C 2 T X (MXene) flakes which function as co-catalysts, facilitating the charge transfer of the photogenerated carriers and reducing the charge recombination on the BiVO 4 surface. Our findings provide a facile re-annealing strategy and a novel two-dimensional (2D) material of Ti 3 C 2 T X (MXene) as co-catalysts to improve the performance of the BiVO 4 photoanode for PEC water oxidation.