A Unique Etching-Doping Route to Fe/Mo Co-Doped Ni Oxyhydroxide Catalyst for Enhanced Oxygen Evolution Reaction

Fe-doped Ni (oxy)hydroxide shows intriguing activity toward oxygen evolution reaction (OER) in alkaline solution, yet it remains challenging to further boost its performance. In this work, a ferric/molybdate (Fe³⁺ /MoO₄ ^2- ) co-doping strategy is reported to promote the OER activity of Ni oxyhydroxide. The reinforced Fe/Mo-doped Ni oxyhydroxide catalyst supported by nickel foam (p-NiFeMo/NF) is synthesized via a unique oxygen plasma etching-electrochemical doping route, in which precursor Ni(OH)₂ nanosheets are first etched by oxygen plasma to form defect-rich amorphous nanosheets, followed by electrochemical cycling to trigger simultaneously Fe³⁺ /MoO₄ ^2- co-doping and phase transition. This p-NiFeMo/NF catalyst requires an overpotential of only 274 mV to reach 100 mA cm^-2 in alkaline media, exhibiting significantly enhanced OER activity compared to NiFe layered double hydroxide (LDH) catalyst and other analogs. Its activity does not fade even after 72 h uninterrupted operation. In situ Raman analysis reveals that the intercalation of MoO₄ ^2- is able to prevent the over-oxidation of NiOOH matrix from β to γ phase, thus keeping the Fe-doped NiOOH at the most active state.