Copper-Induced Formation of Structurally Ordered Pt–Fe–Cu Ternary Intermetallic Electrocatalysts with Tunable Phase Structure and Improved Stability

In this work, the atomic arrangement in PtFexCu1–x ternary-ordered intermetallic nanoparticles has been shown to represent an accurate and flexible structure-controlled strategy to optimize its electrocatalytic performance in the methanol oxidation. The presence of Cu in PtFexCu1–x facilitates the phase transformation from a chemically disordered face-centered cubic (fcc) structure to an ordered body-centered tetragonal (bct) PtFe phase at lower annealing temperatures. These ordered structures exhibit significantly enhanced activity and stability when compared to the disordered counterparts because of not only the robust bct-PtFe ordered structure but also the relatively inert Cu partially replacing Fe to mitigate the dissolution of the non-noble metals. Among these series of ordered PtFexCu1–x materials, PtFe0.7Cu0.3 exhibited the best durability, arising, in part, from the optimal Cu concentration (Cu:Fe = 3:7). When additional Fe was replaced by Cu atoms, the ordered structure was destroyed, triggered by the loss of Cu, leading to severe leaching of the transition metals and the loss of durability. Incorporation of Cu also led to the lattice changes and the stronger adsorption of CO-like species, thereby decreasing the electrocatalytic activity for the methanol oxidation reaction. However, this represents an acceptable compromise given the remarkable improvement in durability.