Online FTIR and Mass Spectrometry Study of Direct Methyl Formate Electro-oxidation for Fuel-Cells Application

We examined the electro-oxidation of methyl formate on a ternary nanocatalyst supported on a multiwall carbon nanotube (Pt₃Pd₃Sn₂/MWCNT). Compared to PtRu/C, this nanocatalyst exhibited a 2.5 times higher peak oxidation current (482 mA mg^-1 at 1.00 V vs RHE) for methyl formate oxidation. The oxidation mechanism was studied by online electrochemical Fourier-transform infrared spectrometry and online mass spectrometry. The online spectroscopic studies illustrate that CO₂ from formate oxidation and methanol is formed electrochemically in the first step. In the low potential region (<0.60 V), CO₂ is mainly produced from the oxidation of the formate part, while at high potentials (>0.60 V) it is formed from the methanolic part of methyl formate. Comparison of methyl formate oxidation behavior with its constituent molecules i.e., methanol and formic acid confirms a fully electrochemical methyl formate path besides the widely proposed large-scale chemical hydrolysis of methyl formate within the time scale of the measurement. A comparative study of different catalyst support materials (Vulcan XC72, Black Pearl Carbon 2000, and MWCNT) in aqueous electrolyte and fuel cells revealed superior activity of the MWCNT-supported nanocatalyst owing to its one-dimensional structure, which facilitates ease of accessibility to the fuel.