Application of response surface method (RSM) to investigate the effects of process parameters on the microstructures and specific surface area of hierarchical 3D nanostructured NiCo2O4 electrocatalyst synthesized through hydrothermal method

The hierarchical 3D nanostructured NiCo2O4 was successfully synthesized through facile hydrothermal method for fuel cell electrocatalysis. It was observed that the specific surface area of NiCo2O4 was strongly influenced by the synthesizing parameters namely temperature (T) and reaction time (t) in hydrothermal process. A high specific surface area in electrocatalyst materials is crucial for maximizing the efficiency and effectiveness of electrochemical reactions by providing more active sites, improving reactivity, enhancing mass transport, and reducing the utilization of expensive catalyst materials. The response surface method (RSM) coupled with central composite design (CCD) was utilised to statistically specify the effects of the reaction time and temperature on the specific surface area of the synthesized NiCo2O4. The optimum synthesize parameters of T = 188.41 °C and t = 12.86 hours were performed to obtain the highest specific surface area of 166.98 m2 g-1 which demonstrated the RSM was an excellent tool to implement and tailor the specific surface area of NiCo2O4. Finally, a mathematical model was derived to predict the relationship between these parameters and the structural properties. This study proved that the optimum hydrothermal parameters improved the final electrocatalyst structures based on numerical analysis and validated by the observation from field emission scanning electron microscopy and calculation from Brunauer–Emmett–Teller (BET) measurement.