Optimization of Pulse Electrodeposited Ni–Se Electrode Modified by Hydrothermally Reduced Graphene Oxide via Response Surface Methodology toward Developing Water-Splitting Electrode

In this paper, the design of experiments (DOE) optimization was carried out via response surface methodology (RSM) based on central composite design (CCD) to investigate the impact of four main pulse reverse electrodeposition factors involved in the deposition of hydrothermally reduced graphene oxide (rGO) on nickel foam (NF). Furthermore, optimization with the same method was performed on pH and Se/Ni ion source ratio to achieve the best electrolyte for cathodic pulse electrodeposition of Ni–Se on the optimized rGO@NF electrode. Therefore, a high reduction degree of GO was achieved via hydrothermal reduction before electrodeposition, which was further enhanced by cathodic reverse pulses. RSM revealed desirable models for both processes. The X-ray diffraction (XRD) investigation indicated an amorphous Ni–Se structure, which holds many advantages for electrocatalytic activity. Moreover, the optimized Ni–Se@rGO@NF exhibited coin-like nanostructures on the field emission scanning electron microscopy (FESEM) images, providing a highly exposed surface area. As demonstrated in electrochemical investigations, the optimized Ni–Se@rGO@NF required 63, 185 mV, and 1.509 V to attain 10 mA·cm –2 for HER, OER, and bifunctional water splitting, respectively. Moreover, an excellent C dl value of 106.55 mFs n –1 /cm 2 for the Ni–Se@rGO@NF suggested a high accessibility of the optimized electrode.