Rare-earth element doped NiFe-MOFs as efficient and robust bifunctional electrocatalysts for both alkaline freshwater and seawater splitting†

Based on the target of carbon neutrality, it is very important to explore highly active and durable electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a series of NiFe-based metal–organic frameworks (MOFs) with the doping of various rare-earth elements (Ce, Y, and La) were in situ grown on nickel foam by a facile solvothermal process. The representative CeNiFe-MOF showed amazing OER performance with ultralow overpotentials of 224 and 277 mV at 500 mA cm⁻² in 1.0 M KOH and 1.0 M KOH + seawater, respectively. Moreover, it also exhibited favorable activity and durability for both alkaline freshwater and seawater splitting. Theoretical calculations unveiled that Ce doping effectively optimized the adsorption energy of H* and reduced the energy barrier from *OH to *O, thus leading to significant promotion of HER and OER performance. This work provided new inspiration for the electron modulation and activity optimization of MOF-based electrocatalysts.