Self-etching assembly of designed NiFeMOF nanosheet arrays as high-efficient oxygen evolution electrocatalyst for water splitting.

2D metal-organic frameworks (MOFs) have emerged as potential candidates for electrocatalytic oxygen evolution reactions (OER) due to their inherent properties like abundant coordination unsaturated active sites and efficient charge transfer. Herein, a versatile and massively synthesizable self-etching assembly strategy wherein nickel-iron foam (NFF) acts as a substrate and a metal ion source. Specifically, by etching the nickel-iron foam (NFF) surface using ligands and solvents, Ni/Fe metal ions are activated and subsequently reacted under hydrothermal conditions, resulting in the formation of self-supporting nanosheet arrays, eliminating the need for external metal salts. The obtained 33 % NiFeMOF/NFF exhibits remarkable OER performance with ultra-low overpotentials of 188/231 mV at 10/100 mA cm-2, respectively, outperforming most recently reported catalysts. Besides, the built 33 % NiFeMOF/NFF(+)||Pt/C(-) electrolyzer presents low cell voltages of 1.55/1.83 V at 10/100 mA cm-2, superior to the benchmark RuO2 (+)||Pt/C(-), implying good industrialization prospects. The excellent catalytic activity stems from the modulation of the electronic spin state of the Ni active site by the introduction of Fe, which facilitates the adsorption process of oxygen-containing intermediates and thus enhances the OER activity. This innovative approach offers a promising pathway for commercial-scale sustainable energy solutions.