Cuprous sulfide intermediate assisted synthesis of PtCu3 intermetallic electrocatalysts in multigram scale for oxygen reduction

Abstract

Small-sized Pt-based intermetallic compounds (IMCs) with unique electronic and geometrical structures are promising candidates as next-generation oxygen-reduction reaction (ORR) catalysts in proton-exchange membrane fuel cells (PEMFCs). However, the synthesis of IMC catalysts remains challenging owing to the trade-off relation between the alloying/ordering degree and particle aggregation/sintering under a high-temperature annealing process. Herein, we demonstrate a cuprous sulfide (Cu_1.96S) intermediate-assisted strategy for the scalable synthesis of PtCu₃ intermetallic electrocatalysts on an S-doped carbon black support. We identify that the Cu_1.96S intermediate formed at low temperature gradually releases metallic Cu species at high temperatures to form a small-sized and uniform Pt–Cu alloy with target stoichiometry, which eventually ensures the formation of well-ordered intermetallic PtCu₃ structures. The prepared intermetallic PtCu₃ catalysts exhibit enhanced ORR performance with a mass activity of 3.2 A mg_Pt⁻¹ and retain 72% of the initial activity after durability tests.