Theoretical Insights into the Electrochemical Stability\nof Pt-Based Intermetallic Compounds

Pt-based\nintermetallic compounds (IMCs) with ordered atomic arrays\nof constituent metals have drawn increasing attention for energy conversion\napplications, but a deep understanding of their electrochemical stability\nis still missing. In this work, using a scheme combining density functional\ntheory (DFT) calculations with experimental thermodynamic data, we\nexplore key factors affecting the phase stability of 25 L1<sub>2</sub>-Pt<sub>3</sub>M IMCs in aqueous media. We show that L1<sub>2</sub>-Pt<sub>3</sub>M IMCs maintain their metal phase at reductive potentials\nbut will dissolve into Pt- and M-derived oxides or dissolved species\nat oxidative conditions. We identify the reduction potential of the\nM metal and the formation energy of the IMC as the two key factors\naffecting the aqueous stability of L1<sub>2</sub>-Pt<sub>3</sub>M\nIMCs. Interestingly, including either early or late metals into the\nintermetallic structure can both enlarge the potential range for stabilizing\nthe metal phase of L1<sub>2</sub>-Pt<sub>3</sub>M IMCs, which can\nbe attributed to the formation of Pt-M quasi-covalent structural networks\nmediated by the d-d orbital hybridizations.