Oxygen vacancies endow atomic cobalt-palladium oxide clusters with outstanding oxygen reduction reaction activity

Considering the technological importance of fuel cells, developing highly efficacious, durable, and Platinum (Pt) -free catalysts are crucial. In this work, we propose a novel nanocatalyst (NC) comprising oxygen vacancies (OV) enriched atomic CoPdOx clusters (CoPdOxV) anchored Pd nanoparticles (NP)s on cobalt-oxide support (denoted as CPCo). As-prepared CPCo NC with an additional 3 wt% of Co decoration (denoted as CPCo-3) delivers an exceptionally high mass activity (MA) of 4394 mAmgCo-1 at 0.85 V vs RHE and 426 mAmgCo-1 at 0.90 V vs RHE in alkaline oxygen reduction reaction (ORR) (0.1 M KOH), which surpasses the commercial J.M.-Pt/C (20 wt%) catalyst by 65-times. More importantly, the CPCo-3 NC exhibits outstanding durability in an accelerated dura-bility test (ADT) with a progressively increased MA by 40 % (6,140 mAmgCo-1) as that of the initial condition after 20 k cycles. Through in-depth physical characterization, electrochemical analysis, and in-situ X-ray absorption spectroscopy (XAS), we demonstrated the conceptual framework of potential synergism between the CoPdOxV and neighbouring metallic Pd-sites. In this event, the surface-anchored CoPdOxV species coupling with OV promotes the O2 splitting, while the neighbouring Pd-sites simultaneously trigger the Oads relocation (i.e. OH- desorption) step. In addition, the cobalt oxide support underneath assists the electron injection to surface Pd-sites. This work not only marks a step ahead for designing high-performance transition metal oxide catalysts for fuel cells but also uncovers the material's aspects of cobalt that shall spark motivation for the other catalytic applications.

Automated summary

Considering the importance of fuel cells, developing highly efficient and durable platinum-free catalysts is crucial. This study proposes a novel nanocatalyst, which consists of oxygen vacancies enriched atomic CoPdOx clusters anchored Pd nanoparticles on a cobalt-oxide support. The resulting nanocatalyst demonstrates exceptional mass activity and durability in the oxygen reduction reaction, surpassing the commercial catalyst by 65 times. The study also reveals the potential synergism between CoPdOxV and metallic Pd-sites, providing insights for designing high-performance catalysts.