Design of type II quaternary double-decker heterostructure Cu-WO3-BiVO4-Bi2S3NiOOH photoanode for stable and efficient photoelectrochemical water splitting

Background

Bismuth vanadate (BiVO₄) and nickel oxyhydroxide (NiOOH) are the prominent photo(electro)catalysts for water-splitting photoelectrodes. The strong visible light absorbers of the Bi₂S₃ decorated type II photoanode of WO₃/BiVO₄/NiOOH efficiently improve the photo-excitons in the photoanodes.

Methods

In this work, type II semiconductors heterostructure photoanodes are fabricated as Cu:WO₃/BiVO₄/Bi₂S₃/NiOOH. The bottom layer of heavily Cu- doped n-type WO₃ nanoplatelets is grown on FTO to make nano-heterostructure Cu:WO₃/BiVO₄ photoanodes. The Bi₂S₃ semiconductor has been grown on the BiVO₄ by chemical bath deposition and NiOOH deposited using the photo-assisted electrodeposition method. The resulting periodically ordered BiVO₄/WO₃ platelets distinctly outperform by the Bi₂S₃ and NiOOH-decorated quaternary photoanodes.

Significant findings

As a result, the as-prepared photoanode shows a high photocurrent density of 6.85 mA cm⁻² at 0 V vs. Ag/AgCl under the irradiation of 100 mW/cm² AM 1.5 G simulated sunlight. With the higher photoactivity of Bi₂S₃ and NiOOH cocatalysts, the photoanode substantially gains stability at higher saturation photocurrents. Overall, the photoanode resulted in a low charge transfer resistance (387.4 Ohm.cm²) and a higher built-in potential of 180 mV, with 2.67 % of ABPE and 2.1 % of STH efficiencies at 0.3 V vs. Ag/AgCl.