Surface Composition and Lattice Ordering-Controlled Activity and Durability of CuPt Electrocatalysts for Oxygen Reduction Reaction

Abstract

We report the enhanced activity and stability of CuPt bimetallic tubular electrocatalysts through potential cycling in acidic electrolyte. A series of CuPt tubular electrocatalysts with sequential increased lattice ordering and surface atomic fraction of Pt were designed and synthesized by thermal annealing to reveal their improved electrocatalytic properties. These low-Pt-content electrocatalysts with Pt shell are formed through the thermal annealing and following potential cycling treatment. The catalysts (C1) with a low atomic fraction of Pt on the surface and low lattice ordering in the bulk are treated in acidic electrolyte, resulting in the formation of a Pt shell with relatively low activity and stability. However, the catalysts (C2) with a Pt-rich surface and high lattice ordering have a highly enhanced electrochemical surface area after potential cycling via surface roughing. The rough Pt shell of the C2 catalysts is achieved by leaching of surface Cu and the concomitant morphology restructuring. The C2 Pt surface demonstrated highly improved specific and mass activities of 0.8 mA cm_Pt^–2 and 0.232 A mg_Pt^–1 at 0.9 V for oxygen reduction reaction (ORR), and after 10 000 cycles, the C2 catalysts display almost no loss of the initial electrochemical active surface area (ECSA). Meanwhile, the stability of these CuPt catalysts shows regular change. Moreover, after a long-term stability measurement, the ECSA of C2 catalysts can be restored to the initial value after another potential cycling treatment, and thus, this kind of electrocatalyst may be developed as next-generation restorable cathode fuel cell catalysts