Cerium‐Modified Cobalt Iron Alloy for Enhanced Alkaline Water Splitting Performance

Abstract Developing efficient nonprecious metal catalysts for alkaline water splitting is crucial. Herein, cerium (Ce)‐modified CoFe alloy‐hydroxide catalysts (Ce 24% ‐CFAH/NF and Ce 2% ‐CFAH/NF) with oxygen vacancies are synthesized via electrodeposition. Ce introduction significantly enhances catalyst turnover frequency (TOF). For oxygen evolution reaction (OER), Ce 24% ‐CFAH/NF achieves a TOF of 0.77 s −1 at 1.50 V versus RHE, vastly exceeding CoFe/NF (0.03 s −1 ). For hydrogen evolution reaction (HER), Ce 2% ‐CFAH/NF achieves 0.66 s −1 at −0.25 V versus RHE, outperforming CoFe/NF (0.22 s −1 ). Consequently, Ce 24% ‐CFAH/NF exhibits excellent OER performance (η 10 = 227 mV, Tafel slope = 32.5 mV dec −1 ), requiring only 290 mV overpotential for 500 mA cm −2 with 85 h stability. Ce 2% ‐CFAH/NF shows superior HER performance ( η 10 = 100 mV, Tafel slope = 60.7 mV dec −1 ). An electrolyzer using both catalysts require only 1.63 V for 10 mA cm −2 and maintains stability (∼100 mA cm −2 for 24 h). The enhanced OER performance is attributed to high oxygen vacancies (3.0 × 10 12 spins/mg) and TOF (0.77 s −1 ), while the HER performance stems from high TOF (0.66 s −1 ) and large electrochemically active surface area (ECSA: 2.35 mF cm −2 / 58.75 cm 2 ). Furthermore, in situ Raman spectroscopy reveals the generation of highly reactive CoFeOOH phases during the OER process.