Infrared spectroscopic study of methanol and formic acid absorbates on a platinum electrode: Part II. Role of the linear CO(a) derived from methanol and formic acid in the electrocatalytic oxidation of CH3OH and HCOOH

Abstract The formation and oxidation of the linear CO(a) from CH 3 OH and HCOOH on a platinum electrode in 0.5 M H 2 SO 4 has been studied by using in-situ polarization modulated infrared reflection-absorption spectroscopy as a function of the electrode potential. The formation from CH 3 OH is greatly reduced in the hydrogen region, while from HCOOH it occurs more readily in the hydrogen region than at 0.4 V (vs. RHE). Linear CO(a) is oxidized off the Pt surface in a narrow potential range around 0.5 V, after which the rate of the electrooxidation of CH 3 OH and HCOOH increases sharply. The poisoning effect of linear CO(a) was also confirmed by the rapid development of the infrared absorption intensity of the linear CO(a) band during continuous decrease of the electrocatalytic activity with time while the electrode was held at 0.4 and 0.2 V for methanol and formic acid, respectively. Reaction schemes to produce CO(a) from HCOOH and CH 3 OH in both the hydrogen region and the double-layer region are proposed.

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