Effects of electrodeposition synthesis parameters on the photoactivity of nanostructured tungsten trioxide thin films: Optimisation study using response surface methodology

The main aim of this study was to synthesize and characterise nanostructured tungsten trioxide (WO3) thin films via electrodeposition and subsequently, optimise the electrodeposition synthesis parameters using response surface methodology (RSM). Statistical Box-Behnken RSM design was used to investigate and optimise the effects of four independent electrodeposition synthesis parameters, namely: deposition time, precursor tungsten (W) concentration, annealing temperature and pH. In addition, the synergistic interaction between different electrodeposition synthesis parameters was identified and quantified in enabling a higher photoactivity achievable by nanostructured WO3 thin films. From the Box-Behnken RSM design, it was found that the optimum deposition time, precursor W concentration, annealing temperature and pH were: 60 min, 0.15 mol/L, 600 ℃, and pH 1.0, respectively. The highest photocurrent density of 120 µA/cm2 was measured at 1 V (versus Ag/AgCl) for nanostructured WO3 thin film synthesized at the optimum conditions as informed by the Box-Behnken RSM. Further analysis and validation of the Box-Behnken RSM model using analysis of variance (ANOVA) revealed that the RSM-derived statistical predictive model was robust, adequate and representative to correlate the various electrodeposition synthesis parameters to photocurrent density.59