Surface dual-oxidation induced metallic copper doping into NiFe electrodes for electrocatalytic water oxidation

Although NiFe-based (oxy)hydroxides species have been recognized as one of the most promising water oxidation catalysts, existing synthetic methods are difficult to fulfill the requirements of catalytic performance, lifetime and large-scale production. Here, we develop a scaled-up and simple dual-oxidative etching strategy for introducing metallic copper into a NiFe hydroxide nanosheet array on a Ni foam electrode (Cu-NiFe LDH/NF) for the oxygen evolution reaction. This dual-oxidation strategy is achieved via a galvanic-corrosion reaction between the metallic Ni template and ions with higher reduction potential (Fe³⁺ and Cu²⁺). The as-prepared electrode exhibits unparalleled activity toward water oxidation with an overpotential of 185 mV at a current density of 10 mA cm^-2 and Tafel slope of merely 30 mV dec^-1, respectively. More importantly, this inexpensive and simple manufacturing technique affords the Cu-NiFe LDH/NF electrode excellent activity retention for over 1200 hours.