Zirconium oxide-based compound as new cathode without platinum group metals for PEFC

摘要

Partially oxidized zirconium carbonitrides (Zr-CNO) powders were evaluated as a non-precious cathode for polymer electrolyte fuel cells (PEFCs). Zr-CNO powders were prepared from zirconium carbonitrides (Zr-CN) with heat-treatment under 0.25%O_2/2%H_2/N_2 at 1000 - 1400℃. The slow scan voltammetry was performed to evaluate the catalytic activity for the oxygen reduction reaction (ORR) under nitrogen and oxygen in 0.1 mol dm~(-3) H_2SO_4 at 30℃. Although the onset potential of ORR for untreated Zr-CN is 0.55 V vs. reversible hydrogen electrode (RHE), the onset potential of the appropriate oxidized Zr-CNO reached 0.97 V vs. RHE. XRD and XPS data suggested that the surface of the Zr-CNO was oxidized to ZrO_2 and Zr-CN remained in the inner part of the each particle. The existence of tetragonal and/or cubic ZrO_2 in the XRD patterns of the Zr-CNO suggested that the vacancies on the surface of the Zr-CNO might affect the catalytic activity for the ORR.