High-performance vertically aligned Bi2O3 nanosheet arrays for water splitting applications by controlling the chemical bath deposition method parameters (precursor concentration and pH)

In this work, vertically aligned β-Bi₂O₃ nanosheet arrays are deposited on FTO using a simple, cost-effective, low-temperature, and easy-tunable technique called chemical bath deposition. Coatings were deposited through selective correlation of varying bismuth ion concentrations at fixed pH and, also, a fixed bismuth ion concentration at different pH values to optimize their structure, morphology, and optical properties. With an increase in bismuth precursor concentration from 0.008 M to 0.5 M, a more crystallized and compact coating with finer nanosheets was formed. Low pH values tended to result in either no coating or a coating composed of discrete particles. As the pH increased to the optimal level, a thicker and more compact coating with a morphology made of thicker and wider nanosheets was formed. Further increase in pH led to a non-uniform coating composed of small and large nanosheets that could not cover the entire surface of the substrate. The optimized photoelectrode exhibited a maximum photocurrent density of 470 μA/cm² at 1.23 V_RHE under 100 mW/cm² simulated sunlight, which is among the top recorded values of Bi₂O₃ photoelectrodes.