摘要
We propose a hierarchically structured quaternary catalyst, consisting of Pd patches on an oxygen vacancy-rich cobalt oxide support, with surface-anchored PtxNiy atomic species (referred as CPNP). The CPNP catalyst exhibits the specific activity of 38.75 mA cm⁻2 and a mass activity of 2901 mA mgPt⁻1 at 0.85 V vs. the reversible hydrogen electrode (RHE), outperforming the commercial J.M.-Pt/C (20 wt%) catalyst by 148 and 43 times, respectively, in alkaline ORR (0.1 M KOH). Furthermore, the CPNP catalyst achieved a half-wave potential of 0.940 V vs. RHE, an improvement of 46 mV over its initial value (0.894 V vs. RHE) after 10,000 accelerated durability test (ADT) cycles. Using in-situ X-ray absorption spectroscopy at the Co-K, Ni-K, Pd-K, and Pt-L₃ edges, we elucidated that the superior ORR performance of the CPNP catalyst arises from the synergistic interaction between oxygen vacancies in the cobalt oxide support and the Ni, Pd, and Pt domains. Specifically, oxygen vacancies and Pt sites facilitate O₂ splitting, while nearby Ni sites promote subsequent hydration steps. Notably, the Pd patches serve as the channel for electron transport from the cobalt oxide support to the Ni sites and also relocates the adsorbed O-atoms to the Ni-sites for subsequent hydration step.
The outstanding ORR performance of CPNP catalyst originates from the local synergy between oxygen vacancies in cobalt-oxide support, Ni, Pd and Pt domains, where oxygen vacancies and Pt sites promote the O2 splitting while adjacent Ni sites boost the subsequent hydration step. More importantly, the Pd patches serve as the channel for electron transport from cobalt-oxide support to Ni-sites. [Display omitted]
•A hierarchically structured quaternary catalyst is developed for ORR.•It surpasses the commercial J.M.-Pt/C catalyst in alkaline ORR.•It shows progressively increasing E1/2 up to 10 K stability test cycles.