Cerium-Doping and Nitridation Effects on Nickel-based Metal Organic Framework for Alkaline Water Oxidation

Abstract

In the quest for a green energy future, renewable energy-driven hydrogen production via alkaline water electrolyzers leads toward a sustainable human society. However, the complementary oxygen evolution reaction (OER) in alkaline water electrolysis limits the overall electrolyzer efficiency since it requires complex, multi-step electron transfer. This work introduces a synthetic strategy that translates a less-conductive Ce-doped nickel metal-organic framework (MOF) into a conductive precatalyst (i.e., a Ce-doped nickel nitride and carbon-based material composite) through nitrogen incorporation. The impact of nitrogen incorporation leads to the formation of a nitride phase, and a carbon-based material phase, while the Ce 3+ species leads to the formation of pseudo-tetrahedral geometries on Ni sites, which enhances OER kinetics marked by a Tafel slope of 83.6 mV dec -1 . Nitridation led to approximately 50× improvement in OER activity relative to the parent MOFs. Moreover, the combined effect of cerium doping and nitridation produced a synergistic effect with Ce0.03Ni0.97-NMOF, achieving a Faradaic efficiency of 100% and maintaining stable operation for 24 hours at a current density of 10 mA cm -2 , exhibiting even higher activity after prolonged testing.