NiFe Nanocatalysts Doped with Mo and Sulfate as Highly Efficient Electrocatalysts for the Large Current-Density Oxygen Evolution Reaction

Nickel–iron-based materials constitute impressive pre-electrocatalysts to reduce the reaction barrier of the alkaline oxygen evolution reaction (OER) for high-efficiency hydrogen production via the carbon-neutral water-splitting system. However, its electrocatalytic ability is inevitably repressed because of the tardy electrochemical reconstruction into the highly active oxyhydroxide species in the layered double hydroxide (LDH) electrocatalyst amid the OER. Herein, the electrochemical reconstruction of NiFe materials is efficiently facilitated via a dual anion functionalization approach, thereby achieving superior and durable OER performance. The sulfate and molybdate anion regulation is easily realized via the rapid erosion of the commercial NiMo foam (NMF) in a dilute solution of FeCl3·6H2O and Na2S2O3·5H2O. The sulfate addition can exert two salient effects: sulfate can interact with nickel to form a unique NiSO4 phase and the S incorporation can quicken the Mo leaching to trigger the redistribution of electron density between Ni and Fe. Thus, the d-band centers of metal sites are tailored to promote the electrochemical reconfiguration into highly active NiFe oxyhydroxides with the elevated valent metal cation during the OER operation. These virtues advantage the efficient and durable OER process even at an industry-level current density. Finally, the NiFe catalyst with the strong binding force of catalytic coating delivers excellent OER performance regarding an ultralow overpotential of only 217 mV at a current density of 10 mA cm–2, the rapid kinetics (40.1 mV dec–1), and a 1466 h ultralong-lasting lifetime to maintain an industrial-level current density of 1 A cm–2. This insight into the anion effect offers an exciting avenue to devise other high-efficiency electrocatalysts.