Nanostructured Bi2S3/WO3 heterojunction films exhibiting enhanced photoelectrochemical performance

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.