Stabilizing Lattice Oxygen Evolution with Oxophilic Ce and Active Ni Oxide Composite Electrocatalysts for Efficient...

In transition metal oxide (TMO) based oxygen evolution reactions (OER) electrocatalysts, the lattice oxygen-mediated mechanism (LOM) has emerged as a more efficient pathway for OER compared to the traditional adsorbate evolution mechanism (AEM). LOM activation critically depends on covalency of transition metals (TMs) with high-valence states. In this study, we leverage the high electron affinity and strong oxophilicity of cerium (Ce) to fine-tune the TM-O bonding state of NiO through a one-step electrodeposition method. Ce and Ni co-electrodeposition forms a CeO₂/NiO heterostructure that shifts from AEM to LOM via enhanced covalency between high- valence Ni and lattice oxygen and promotes electron transfer from NiO to CeO₂. This CeO₂/NiO heterostructure achieves a low overpotential of 160 mV and a Tafel slope of 32.68 mV dec^⁻1 at 10 mA cm^⁻2. Additionally, it exhibits a low cell voltage of 1.84 V and only a 1.19% voltage increase over 100 h at a high current density of 1 A cm^⁻2 in an anion exchange membrane water electrolyzer. These results represent the role of oxophilic Ce and CeO₂ in stabilizing the Ni oxidation states, thereby ensuring superior LOM-driven OER performance.