Hierarchical Cu Nanoarray/NiFe Hydroxide Nanostructures for Efficient Electrochemical Water Oxidation

Three-dimensional (3D) hierarchical nanostructures have shown great promise for electrocatalysis, while a conductive core is paramount to boost the ultimate catalytic activity. In the present study, hierarchical NiFe hydroxide–Cu arrays are prepared through solution etch and sequential electrolysis as the electrocatalysts for oxygen evolution reaction (OER). The electrochemically reduced Cu nanoarrays as the core provide superior conductivity for electron transfer, while the unique hierarchical 3D structure provides a large active surface area, a short ion diffusion path, and open channels for efficient gas release. The resulting NiFe hydroxide–Cu arrays on copper foam (CF) exhibit outstanding catalytic performance of 245 and 300 mV, respectively, to achieve current densities of 10 and 100 mA cm–2 in a 1 M KOH solution. A small Tafel slope of 51 mV dec–1 and superior electrochemical durability of up to 100 h are also demonstrated.