Hierarchical Superhydrophilic/Superaerophobic Ni(OH)₂@NiFe-PBA Nanoarray Supported on Nickel Foam for Boosting the Oxygen Evolution Reaction

Abstract

The design of hierarchical electrocatalysts with plentiful active sites and high mass transfer efficiency is critical to efficiently and sustainably carrying out the oxygen evolution reaction (OER), which presents a challenging and pressing need. In this study, a hierarchical Ni(OH)₂@NiFe-Prussian blue analogue nanoarray grown on nickel foam (NF) [labeled as Ni(OH)₂@NiFe-PBA/NF] was synthesized by combining a mild electrodeposition method with an ion-exchange strategy. The resultant Ni(OH)₂@NiFe-PBA/NF displays superhydrophilic/superaerophobic properties that optimize the contact with the electrolyte, improve mass transfer efficiency, and expedite detachment of O₂ bubbles during the electrocatalytic OER. Specifically, Ni(OH)₂@NiFe-PBA/NF exhibits exceptional capability in the OER with low overpotentials of 224 and 240 mV at the current densities of 50 and 100 mA cm^-2, respectively, accompanied by a low Tafel slope of 37.1 mV dec^-1 and outstanding stability over 100 h at a fixed potential of 1.78 V vs reversible hydrogen electrode (RHE). Furthermore, Ni(OH)₂@NiFe-PBA/NF demonstrates remarkable OER performance even in alkaline simulated seawater. During the OER process, active metal-OOH intermediates were formed by the partial self-reconstruction of NiFe-PBA in the heterostructure, as revealed by in situ Raman spectroscopy.