Nanostructured Bi2S3/WO3 heterojunction films exhibiting enhanced photoelectrochemical performance

Abstract

To improve the photoelectrochemical activity of WO₃, Bi₂S₃/WO₃ heterojunction films were designed by coupling WO₃ films with varying amounts of urchin-like Bi₂S₃ nanospheres. The WO₃ films were composed of WO₃ nanoprism arrays, which were synthesized using a solvothermal method. After coating a single layer of Bi₂S₃ on top of the WO₃ film, the resulting Bi₂S₃/WO₃ heterojunction film showed enhanced photoelectrochemical activity. At 1.2 V vs. Ag/AgCl, the initial photocurrent density of the Bi₂S₃/WO₃ heterojunction film with one layer of Bi₂S₃ was 1.33 mA cm⁻² in 0.1 M Na₂SO₄ and 1.19 mA cm⁻² in a 0.2 M NaCl mixed water–ethanol solution, which was 40% and 32% higher than the bare WO₃ film under the same conditions, respectively. The optimal number of Bi₂S₃ layers for coupling with the WO₃ film was found to be 3 layers, which had the highest photocurrent density and IPCE values. The photoelectrochemical activity of Bi₂S₃/WO₃ heterojunction film was not stable for water oxidation due to photocorrosion in aqueous electrolyte, but it was stable in the NaCl mixed water–ethanol solution and a non-aqueous solution containing iodide/triiodide as a redox couple. The origin of enhanced photoelectrochemical activity of the Bi₂S₃/WO₃ heterojunction film was primarily ascribed to the band potential matching between WO₃ and Bi₂S₃, which is advantageous for charge separation.