Theoretical Insights into the Electrochemical Stability of Pt-Based Intermetallic Compounds

Pt-based intermetallic compounds (IMCs) with ordered atomic arrays of constituent metals have drawn increasing attention for energy conversion applications, but a deep understanding of their electrochemical stability is still missing. In this work, using a scheme combining density functional theory (DFT) calculations with experimental thermodynamic data, we explore key factors affecting the phase stability of 25 L1₂-Pt₃M IMCs in aqueous media. We show that L1₂-Pt₃M IMCs maintain their metal phase at reductive potentials but will dissolve into Pt- and M-derived oxides or dissolved species at oxidative conditions. We identify the reduction potential of the M metal and the formation energy of the IMC as the two key factors affecting the aqueous stability of L1₂-Pt₃M IMCs. Interestingly, including either early or late metals into the intermetallic structure can both enlarge the potential range for stabilizing the metal phase of L1₂-Pt₃M IMCs, which can be attributed to the formation of Pt-M quasi-covalent structural networks mediated by the d-d orbital hybridizations.