Trimetallic Alloys\nas an Electrocatalyst for Fuel\nCells: The Case of Methyl Formate on Pt<sub>3</sub>Pd<sub>3</sub>Sn<sub>2</sub>

The shift toward renewable energy sources plays a central\nrole\nin the quest for a circular economy. In this context, methyl formate\n(MF) has garnered attention as a compelling hydrogen carrier and alternative\nfuel, because of its remarkable characteristics (energy density, ease\nof storage and transport, and low boiling point). In this study, DFT\ncalculations supported by online electrochemical mass spectroscopy\n(OE-MS) were performed to investigate the MF electro-oxidation (MFEO)\non Pt<sub>3</sub>Pd<sub>3</sub>Sn<sub>2</sub> (111). The DFT calculations\nprovide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt\nand Pd together provide a preferred active site for initiating MFEO\nthrough the O–H bond scission, and Sn plays an essential role\nin the mitigation of CO through oxygenation or water activation. By\ncomparing the reaction energies and activation barriers for all possible\nreactions in MFEO, the suggested path necessitates a minimum energy\nof 0.14 eV to initiate the MFEO. This value was supported by the experimental\nresults, showing that the oxidation wave of MF starts at 0.15 V (70\n°C). Density functional theory (DFT) results, supported by OE-MS,\nindicate that the hydrolysis of MF prior to MFEO is not preferred\non Pt<sub>3</sub>Pd<sub>3</sub>Sn<sub>2</sub> (111) surfaces, although\nthe formation of methanol is plausible via a CH<sub>3</sub>O intermediate.\nAmong the three small organic molecules (SOMs) studiedMF,\nmethanol, and formic acidMF has the lowest activation energy\nfor the initial bond breaking that starts the whole oxidation process\n(0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV);\nthus, MF is the preferred fuel on Pt<sub>3</sub>Pd<sub>3</sub>Sn<sub>2</sub> (111).