Engineering sub-nano structures with highly jagged edges on the Pt surface of Pt/C electrocatalysts to promote oxygen reduction reactions

Abstract

Improving the Pt mass activity (imPt) of electrocatalysts towards the oxygen reduction reactions requires an increase in Pt atom utilization efficiency. Through the combination of Cu underpotential deposition and Pt galvanic replacement (CuUPD-GAL), Pt nanoclusters (Ptcs<1 nm) with highly jagged edges (H-Ptcs) are specifically constructed on the Pt surface of a typical carbon-supported, Pt-nanoparticle (Pt/C) electrocatalyst. The H-Ptcs contribute to an imPt of 21.8 A mgPt−1 (at 0.9 V versus reversible hydrogen electrode), which exceeds that achieved by Pt/C (0.1–0.25 A mgPt−1) by a factor of 200. To facilitate a full-cell evaluation and to mimic the batch flow production of electrocatalysts, a sequential flow injection procedure is developed that enables the direct H-Ptcs modification on a commercial membrane electrode assembly (MEA), the heart of a fuel cell. In a full cell (real fuel cell), the contribution of the H-Ptcs to the current density of 3.5 A cm−2 at 0.7 V and maximum power density of 8.0 W cm−2 is higher than that of state-of-the-art Pt-containing catalysts (<1.5 A cm−2 and <1.4 W cm−2). A hybrid Ptc modification approach, in which an MEA is subjected to two sequential Ptc modification processes, improves the durability of the MEA while maximizing activity.