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 tons) 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) (η10,HER and η10,OER), active surface area (Rf) and intrinsic electrocatalytic activity (i/Rf). The results indicated that η10,HER, η10,OER, and Rf are mainly influenced by duty cycle and electrodeposition time, while i/Rf 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 η10,HER, η10,OER, and Rf, 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.

Facile electrodeposition of ternary Ni-Fe-Co alloy nanostructure as a binder free, cost-effective and durable electrocatalyst for high-performance overall water splitting.

Development of highly effective and stable electrocatalyst as full water electrolyzers is essential for the energy production process. In this study, binder-free and self-made Ni-Fe-Co nanostructure electrode was developed using electrodeposition method, and its electrocatalytic properties were investigated for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. The fabricated electrocatalyst exhibited excellent properties for the evolution of H2 and O2. Ni-Fe-Co nanostructure film required overpotentials of 91 mV for HER and 316 mV for OER in order to create a current density of 10 mA cm-2. Furthermore, the Tafel slope for HER and OER was measured as 86 and 43 mV/dec, respectively. In addition, the resulting electrode showed outstanding electrocatalytic stability, in which following a long period of electrolysis, the necessary overpotential to maintain a current density of 100 mA cm-2 remained constant. This bifunctional electrode enables alkaline water electrolyzers, which can provide a current density of 10 mA cm-2 under a cell voltage of 1.6 V. Such desirable performance of fabricated electrode as an electrocatalyst for full water splitting can be attributed to high active surface area factor, the synergistic effect of the elements, and rapid separation of bubbles from the electrode surface. This study provides a new method for the rapid construction of efficient electrocatalyst for renewable energy sources.