Continuous Fe³⁺ releasing enabled complete reconstruction of Ni-based MOF for promoted water oxidation in industrial alkali

Most oxygen evolution reaction (OER) electrocatalysts show poor stability under industrial alkaline conditions (20–30 wt.% KOH). Therefore, it is essential to develop stable, efficient, and low-cost OER catalysts for industrial water electrolysis. Herein, we present a straightforward approach for the complete electrochemical reconstruction of Ni-BDC, a Ni-based metal-organic framework, for OER. This method involves the continuous release of Fe³⁺ from Fe foam counter electrode in a high-concentration (6.0 M, 25 wt.%) KOH solution. The continuously Fe³⁺ releasing not only realizes in situ Fe³⁺ doping, but also introduces abundant defects in the obtained catalyst during cyclic voltammetry activation, thereby accelerating the electrochemical reconstruction. The reconstructed OER catalyst (Fe-doped nickel hydroxide/oxyhydroxide nanosheets supported on Ni foam, Fe-NiO_x(OH)_y/NF) manifests a low overpotential of 217 mV at 10 mA cm⁻² and 263 mV at 100 mA cm⁻² in 1.0 M KOH. Noteworthy, the Fe-NiO_x(OH)_y/NF also demonstrates high stability in 30 wt.% KOH. This strategy of regulating the electrochemical reconstruction process sheds light on the construction of stable and efficient OER catalysts for industrial water electrolysis.