Nitrogen-doped cobalt phosphate@nanocarbon hybrids for efficient electrocatalytic oxygen reduction

Abstract

The development of efficient non-noble metal electrocatalysts for the oxygen reduction reaction (ORR) is still highly desirable before non-noble metal catalysts can replace platinum catalysts. Herein, we have synthesized a new type of ORR catalyst, Co₃(PO₄)₂C-N/rGOA, containing N-coordinated cobalt phosphate, through the thermal treatment of a phosphonate-based metal–organic framework (MOF). Co₃(PO₄)₂C-N/rGOA exhibits not only a comparable onset potential and half-wave potential but also superior stability to the commercial Pt/C catalyst for the ORR in alkaline solutions (0.1 and 1.0 M KOH). A combination of structural characterization (e.g., XPS, HRTEM, XANES, and EXAFS) and electrochemical analysis shows that the high ORR activity of the Co₃(PO₄)₂C-N/rGOA catalyst should be attributed to the co-existence of N-doped graphitic carbon and the cobalt phosphate with Co–N species that boost the activity of the cobalt phosphate. These findings open an avenue for exploring the use of phosphonate-based MOFs for energy conversion and storage applications.