Hierarchical Bifunctional NiO Electrocatalyst: Highly Porous Structure Boosting the Water Splitting Activity

Abstract The development of an efficient, low‐cost and earth‐abundant electrocatalyst for water splitting is crucial for the production of sustainable hydrogen energy. However their practical applications are largely restricted by their limited synthesis methods, large overpotential and low surface area. Hierarchical materials with a highly porous three‐dimensional nanostructure have garnered significant attention due to their exceptional electrocatalytic properties. These hierarchical porous frameworks enable the fast electron transfer, rapid mass transport, and high density of unsaturated metal sites and maximize product selectivity. Here the process involved obtaining monodispersed microrod‐shaped Ni(OH) 2 through a hydrothermal reaction, followed by a heat treatment to convert it into hierarchical microrod‐shaped NiO materials. N 2 sorption analysis revealed that the BET surface area increased from 9 to 89 m 2 /g as a result of the heat treatment. The hierarchical microrod‐shaped NiO materials demonstrated outstanding bifunctional electrocatalytic water splitting capabilities, excelling in both HER and OER in basic solution. Overpotential of 347 mV is achieved at 10 mA/cm 2 for OER activity, with a Tafel slope of 77 mV/dec. Similarly, overpotential of 488 mV is achieved at 10 mA/cm 2 for HER activity, with a Tafel slope of 62 mV/dec.