Electrochemical behaviors of dimethyl ether on platinum single crystal electrodes. Part II: Pt(1 0 0)

The electrochemical behaviors of dimethyl ether (CH₃-O-CH₃, DME), which is a promising fuel for the fuel cell, on Pt(1 0 0) electrode in 0.5 M H₂SO₄ solution have been investigated in detail by electrochemical and in situ infrared (IR) measurements. As the potential is swept from 0.05 V (vs. RHE) to positive direction at 50 mV s^-1, the dehydrogenation peak of DME is observed around 0.33 V to generate a reaction intermediate and is further converted to carbon monoxide (CO) in more positive potential region. The main peak for DME bulk oxidation locates around 0.80 and 0.72 V in the positive- and negative-going potential sweep, respectively. The positions of these peaks strongly depend on the scan rate. The in situ IR observations show that (CH₃OCH₂-)_ad is an intermediate for the first dehydrogenation step of DME on Pt(1 0 0) surface and can serve as a precursor of the subsequent intermediate of adsorbed CO (CO_ad). Cyclic voltammograms of Pt high index single crystal planes Pt(hkl) show that the direct oxidation of DME is suppressed by decreasing the (1 0 0) terrace width. Based on these results, a possible reaction mechanism for DME electro-oxidation on the platinum single crystal electrode surface is proposed.