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 t_ons) 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/cm² for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) (η_10,HER and η_10,OER), active surface area (R_f) and intrinsic electrocatalytic activity (i/R_f). The results indicated that η_10,HER, η_10,OER, and R_f are mainly influenced by duty cycle and electrodeposition time, while i/R_f is affected by frequency and time. The optimized NiSe₂ electrode synthesized under optimal conditions of pulse electrodeposition (low duty cycle and prolonged electrodeposition time) showed the most desirable values for η_10,HER, η_10,OER, and R_f, equal to 44 mV (vs. RHE), 235 mV (vs. RHE) and 14700, respectively. The nanostructured NiSe₂ demonstrated the highest potential in the bifunctional application of OER and HER.