dc.description.abstract | The Pt/Pd(111) prepared in the previous laboratory has the effect of improving the oxidation of methanol. It is changed to the carrier of the rhodium : (1) The alloy prepared from a high oxygen-containing rhodium and platinum to Study the activity toward methanol oxidation; (2) As one of the catalytic materials commonly was used in the reduction reaction, and there are many literature on the catalysis of nitrate by rhodium recently; therefore, the nitrate reductive activity on specific crystal facets is studied.
In this study, platinum-rhodium alloy was prepared by two methods: electroless plating and electroplating. The structure of the surface was observed by scanning tunneling electron microscopy (STM) and X-ray photoelectron spectroscopy (XPS). It was found that both platinum were deposited on the Rhodium (111) with nanometer scale, but the XPS Pt 4f signal is different, and the activity toward MOR was investigated by cyclic voltammetry (CV). The experimental results show that oxidative potential of Pt NPs/Rh(111) from electroless plating moved up 280 mV than that of Pt(111), and the oxidation peak of the backward sweep can appear in advance at 0.1 V (vs. Ag/AgCl). Through the oxidation of CO experiment, it was also observed that the CO oxidation potential of Pt NPs/Rh(111) was 35~115 mV ahead of Pt(111), it is inferred that rhodium can contribute OH group at low potential, which reduces CO poisoning, so the methanol oxidation activity is enhanced by the synergistic effect of platinum and rhodium—Pt-CO + Rh-OH →Pt + Rh + CO2 + H+ + e−. XPS and roughness also analyzed factors affecting the oxidation potential and current of methanol.
The structure and reaction process of nitric acid adsorption on rhodium (111) were investigated from STM and infrared reflectance absorption spectrometer(IRRAS). It is found that the difference in crystal facet results in different nitrate reduction activities, Tafel slope was performed on the nitrate reduction CV of the (111) and (100) facets, respectively, and 114 and 180 mV dec-1 were obtained, it is considered that the nitrate adsorbed and followed by reduction to nitrite as a rate determining step (RDS), therefore, the (100) crystal plane with poor activity may be due to the geometric effect—the triangular plane structure of NO3- is not easy to adsorb to the simple tetragonal (100) plane. It is also explored whether different pH values and anions have a change in nitrate activity.
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