Lithium-Modified NiCo₂O₄ OER Catalysts with Enhanced Durability under Simulated Renewable Energy Operation in Alkaline Water Electrolysis (Supporting Information)

Hydrogen production via alkaline water electrolysis (AWE) is a key approach for achieving large-scale, carbon-neutral hydrogen generation. However, its long-term durability is challenged by reverse-current events that occur under intermittent renewable power conditions. These events lead to repeated oxidation and reduction cycling of Ni-based anodes, which accelerates structural degradation, particularly in spinel-type NiCo2O4 catalysts that offer high oxygen evolution reaction (OER) activity but limited stability against Co leaching. In this study, we investigate lithium incorporation as a redox and interfacial buffering strategy to improve the electrochemical durability of NiCo2O4-based anodes subjected to repeated redox transitions under intermittent power. Two types of Li-modified catalysts, a (Li)NiO + NiCo2O4 composite and Li-doped NiCo2O4, were synthesized to examine whether the durability enhancement depends on a specific crystalline phase. Although the Li-containing catalysts exhibited distinct bulk structures, both showed significant improvements in reverse-current tolerance while maintaining OER Tafel slopes comparable to pristine NiCo2O4, indicating that the overall reaction mechanism was preserved. Enhanced durability is likely associated with Li-induced structural and electrochemical changes. Oxygen diffusion toward the substrate during Li migration may promote the formation of a Co-free NiOx-rich layer, which in turn enhances adhesion and stabilizes the coating-substrate interface. In addition, Li contributed to the control of the active redox peak from Ni to appear over a longer ADT cycle. Therefore, lithium appears to regulate surface redox behavior and strengthen interfacial stability during repeated cycling. These results demonstrate that lithium incorporation provides an effective strategy to improve the operational reliability of NiCo2O4-based AWE anodes under fluctuating power conditions.