Sustainable water oxidation enabled by a complex-doped cobalt oxide electrode

Achieving sustainable water oxidation presents significant challenges, particularly employing cobalt-based electrocatalysts. Despite promising activities, many cobalt-based electrocatalysts undergo in-situ partial restructuring into disordered (oxy)hydroxides, as indicated by the Pourbaix diagram. This restructuring typically degrades structural integrity and electronic conductivity, undermining catalytic stability. Here, we propose a complex doping strategy to stabilize LiCoO₂, a cobalt oxide that can be sourced from spent lithium-ion batteries, for sustainable water oxidation. Specifically, by co-doping LiCoO₂ with Ni, Fe, and Pd, we mitigate the reconstructed extent of the in-situ generated spinel phase during water oxidation reaction and enhance electrochemical stability. Furthermore, complex doping improves the surface conductivity and facilitates gas removal, boosting mechanical robustness. Consequently, the optimized LiCo_0.79Ni_0.1Fe_0.1Pd_0.01O₂ achieves a competitive water oxidation stability of over 2000 hours. Additionally, in membrane electrolyzer tests, LiCo_0.79Ni_0.1Fe_0.1Pd_0.01O₂ outperforms the benchmark RuO₂, delivering 2.5 A cm^-2 at 1.58 V and maintaining stability for over 1400 hours. By elucidating the role of each dopant in LiCo_0.79Ni_0.1Fe_0.1Pd_0.01O₂, this work offers critical insights for the rational design of sustainable water splitting electrodes.