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

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-02, Vol.454, p.140289, Article 140289
• Main Authors: Yang, Thomas, Bhalothia, Dinesh, Chang, Hong-Wei, Yan, Che, Beniwal, Amisha, Chang, You-Xun, Wu, Shun-Chi, Chen, Po-Chun, Wang, Kuan-Wen, Dai, Sheng, Chen, Tsan-Yao
• Format: Article
• Language: English
• Subjects: Cobalt-palladium; Fuel cells; Oxygen reduction reaction; Oxygen vacancy; Transition-metal-oxide catalysts
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.140289

ORR pathways on the surface of (a) Co@Pd and (b) CPCo-3 NCs at an open-circuit voltage (OCV) and under potential driven conditions from 1.0 to 0.7 V. In Co@Pd NC, the O2 splitting to 2Oads occurs in the Pd surface the Oads is relocated to the neighbouring oxygen vacancies for conducting the reduction reaction with H2O in CoOXV sites. In CPCo-03, the hydration reaction removes the amorphous CoOX and thus expose the CoPdOXV to the electrolyte from OCV to 1.0V. The PdCoOXV sites are reaction centre for the O2 splitting to 2Oads and collaborate with the neighbouring Pd atoms for completing the ORR. [Display omitted] •A novel catalyst of oxygen vacancies enriched atomic CoPdOx clusters is developed.•It delivers a mass activity of 426 mAmgCo−1 at 0.90 V vs RHE in alkaline ORR.•It increases the mass activity by 40 % at 20 k potential cycles in degradation test. 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 durability 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 oth