Spontaneous redox synthesis of Prussian blue/graphene nanocomposite as a non-precious metal catalyst for efficient four-electron oxygen reduction in acidic medium

Abstract

A Prussian blue/graphene (PB/GE) nanocomposite is synthesized as a non-precious metal catalyst by a spontaneous redox reaction in acidic solution with Fe powder, K3[Fe(CN)6], and graphene oxide as precursors. The resulting PB/GE nanocomposite is characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The PB/GE nanocomposite-modified glassy carbon electrode (PB/GE–GCE) exhibits good electrocatalytic activity and long-term stability toward the oxygen reduction reaction (ORR). The reduced form of PB, Prussian white, has favorable electrocatalytic activity for the reduction of O2 and H2O2 in acidic solutions. Rotating ring-disk voltammetric measurements clearly show that the dominant product of ORR at the PB–GCE is water produced by the 4e− reduction of O2 at all potentials. ORR at the PB/GE–GCE occurs mainly inside the PB lattice through the 4e− reduction pathway at E > −0.5 V and on GE nanosheets through the “2 + 2” mechanism involving H2O2 as the intermediate product at E < −0.5 V. The PB/GE nanocomposite is a potentially efficient and cost-effective catalyst for fuel cells.