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

Abstract

Bismuth vanadate (BiVO4) has been envisioned as a promising photoanode material for photoelectrochemical (PEC) water oxidation. However, the PEC performance of BiVO4 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 Ti3C2TX/BiVO4 was fabricated for the first time by spin coating thin Ti3C2TX (MXene) flakes onto the surface of a BiVO4 film grown on the FTO substrate. A facile re-annealing treatment of bare BiVO4/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 (BiVO4/FTO) charge recombination could be effectively suppressed due to the better contact between the BiVO4 film and FTO. The coating of thin Ti3C2TX flakes onto the BiVO4 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 Ti3C2TX (MXene) flakes which function as co-catalysts, facilitating the charge transfer of the photogenerated carriers and reducing the charge recombination on the BiVO4 surface. Our findings provide a facile re-annealing strategy and a novel two-dimensional (2D) material of Ti3C2TX (MXene) as co-catalysts to improve the performance of the BiVO4 photoanode for PEC water oxidation.