Atomic-level Oxygen Vacancy-driven Oxide-Metal Nano-heterointerface Junction Catalyst for High-Efficiency Alkaline Fuel Cells

In this work, we report the rational design and development of a highly efficient and durable heterogeneous catalyst (denoted as CP@Ti-1) for the oxygen reduction reaction (ORR). The catalyst features oxidized Ti single atoms uniformly decorated on Pd nanoparticles supported by Co₃O₄, with a high density of oxygen vacancies simultaneously introduced in both the Ti and Co oxide domains. This unique atomic-scale architecture effectively integrates single-atom catalysis, defect engineering, and interfacial synergy within one system.

Electrochemical evaluations under alkaline conditions demonstrate that CP@Ti-1 delivers exceptional ORR performance, achieving mass activities of 9725 mA mgTi⁻¹ at 0.85 V and 1244 mA mgTi⁻¹ at 0.90 V versus RHE, which are substantially higher than those of commercial Pt/C catalysts. Moreover, CP@Ti-1 exhibits outstanding durability, retaining 100% of its initial activity after 20,000 accelerated degradation test cycles, highlighting its structural robustness and resistance to degradation during long-term operation.

To elucidate the origin of the superior catalytic performance, in situ X-ray absorption spectroscopy (XAS) at the Co, Pd, and Ti K-edges was employed to probe the dynamic electronic and atomic structures under operating conditions. The results reveal a clear division of labor among the active sites: oxygen vacancies associated with oxidized Ti single atoms and Co oxide domains serve as primary sites for O₂ adsorption and dissociation, while adjacent Pd domains facilitate the subsequent hydrogenation of adsorbed oxygen species and the formation of OH⁻ intermediates. This cooperative mechanism effectively lowers the kinetic barriers of key ORR steps and accelerates overall reaction kinetics.

Importantly, this study demonstrates that controlled oxidation of single atoms, traditionally regarded as detrimental, can be transformed into a functional advantage when coupled with oxygen-vacancy engineering. By overcoming the intrinsic limitations of conventional single-atom catalysts—namely insufficient reaction sites and oxidation-induced deactivation—the proposed design

strategy significantly enhances both activity and stability while reducing noble-metal dependency.

Overall, this work provides fundamental insights into oxygen-vacancy–metal interfacial synergy at the atomic scale and establishes a scalable, high-performance ORR catalyst architecture. The findings not only advance the understanding of structure–performance relationships in complex electrocatalysts but also offer a promising materials platform for fuel cells and other clean energy conversion technologies.