An in situ combustion method for scale-up fabrication of BiVO4 photoanodes with enhanced long-term photostability for unassisted solar water splitting

Abstract

The development of large-area, low-cost photoanodes with high efficiency and photostability is pivotal for the commercialization of photoelectrochemical (PEC) water splitting. Here, an in situ combustion process is reported as a new route to the solution growth of bismuth vanadate (BiVO₄) photoanodes. The highly exothermal in situ combustion process ignites rapid solvent evaporation and promotes the homogeneous distribution of BiVO₄ on large-size conductive substrates. Also, the released thermal energy builds tight connection between the BiVO₄ films and the conductive substrates, which suppresses the cathodic photocorrosion and shows unexpected high photocurrent density and ultralong photostability. The as-formed photoanodes can continuously work for sulfite oxidation under consecutive AM 1.5G illumination for ∼190 h with no decay, and for water oxidation for ∼135 h with ∼20% performance decay compared with the initial value. Such a high photostability toward water oxidation has not been reported for large-size BiVO₄ photoanodes previously. A PEC-PV device is fabricated by assembling 9 pieces of combustion-processed large size (25 cm²) BiVO₄ photoanodes for unassisted solar water splitting. The as-assembled device shows a stable photocurrent of up to 0.26 A even after working for 40 sunny days under real solar light irradiation (1 h for each day). Such a facile in situ solution combustion method is promising for scale-up fabrication of large size BiVO₄ photoanodes, and it can also potentially be implemented to fabricate other types of photoelectrodes on conductive substrates and promote their large-scale deployment.