Enhancing Water Oxidation Catalysis on a Synergistic Phosphorylated NiFe Hydroxide by Adjusting Catalyst Wettability

Surface wettability is very important for designing and developing heterogeneous electrocatalysts that can be applied in an aqueous environment. Here, by adjusting the surface wettability of the catalyst using a facile two-step strategy, a porous nanosheet electrocatalyst composed of NiFe hydroxide and NiFe phosphate (denoted as NiFe/NiFe:Pi), has been designed and developed. The two-step strategy not only allows us to successfully control the morphology but also provides an approach to modify the surface chemical property of a catalyst. After phosphorylation, the surface wettability of the NiFe/NiFe:Pi catalyst is significantly enhanced (contact angle 44 ± 3°) in comparison to that of NiFe hydroxide electrode without phosphorylation (contact angle 129 ± 5°). Serving as an oxygen evolution catalyst in 1 M KOH aqueous solution, the NiFe/NiFe:Pi electrode yields strong synergistic oxygen evolution activity to deliver a current density of 10 mA cm–2 with an overpotential merely of 290 mV. The catalyst also exhibits extraordinary high current densities of 300 mA cm–2 at an extremely low overpotential of 340 mV, which is among the best Ni-based OER electrocatalysts to date. The well-maintained open porous nanosheet structure, enhanced surface wettability, and increased charge transfer rate at the NiFe/NiFe:Pi catalyst, together with effective mass transport and enlarged catalytic active sites offered by the hierarchical porous structure, contribute to the extraordinary water oxidation performance.