Optimization of nickel selenide for hydrogen and oxygen evolution reactions by response surface methodology.

In this study, the electrocatalytic activity of Ni-Se electrode synthesized on nickel foam by pulse electrodeposition was optimized through the design of experiments (DOE) approach using the response surface methodology (RSM) for both hydrogen and oxygen evolution reactions. The frequency (f), duty cycle (dc), current density (i), and electrodeposition time (sum of ts) were chosen as the parameters of the pulse electrodeposition method. The analyses of variance (ANOVA) were performed on the responses of the designed experiments that included the required overpotential at the current density of 10 mA/cm for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) (η and η), active surface area (R) and intrinsic electrocatalytic activity (i/R). The results indicated that η, η, and R are mainly influenced by duty cycle and electrodeposition time, while i/R is affected by frequency and time. The optimized NiSe electrode synthesized under optimal conditions of pulse electrodeposition (low duty cycle and prolonged electrodeposition time) showed the most desirable values for η, η, and R, equal to 44 mV (vs. RHE), 235 mV (vs. RHE) and 14700, respectively. The nanostructured NiSe demonstrated the highest potential in the bifunctional application of OER and HER.