关键词: 过渡金属超薄层电极, 铑, 铂, 氢, 一氧化碳, 二氧化碳

Abstract: Pt group metals have been widely used in catalysis such as hydrogenation of organic compounds and the oxidation of carbon monoxide. The information about CO adsorption on the Pt group surfaces and the influence of other surface species, such as hydrogen and CO 2, will be greatly helpful to elucidate the adsorption behavior of CO on Pt group metal surfaces and get a deeper understanding of catalytic mechanisms of Pt group metals. Surface enhanced Raman spectroscopy (SERS) has been becoming an increasingly important means to characterize the electrochemical metal solution interface over the past two decades. Our laboratory has successfully obtained SERS from neat transition metal surfaces, including Pt [1] , Ni [2] , Fe [3] and Co. We are able to observe the SERS of CO and the atop adsorbed H on roughened Pt surfaces [1] . However, compared with Ag, Au and Cu which exhibit great surface enhancement, the weak enhancement of the transition metals make it unsuitable for the detailed study for those adsorbates with very small Raman scattering cross sections. Another method to obtain the SERS signals from Pt group metals has been developed in Weaver's group, which is to electrodeposit ultrathin metal films on SERS active Au surfaces, utilizing the long range effect of the SERS of Au [4,5] .. Recently, they obtained the pinhole free ultrathin (2～5 monolayers, mL) films of Pt group metals over SERS active gold, which can produce intense SERS for chemisorbates bound to the overlayer metal. [6] The important advantage of the improved method is that it can avoid the influence from the SERS active substrate. Further more, the surface enhancement of these metal thin films is higher than that of roughened pure Pt group metals (about 10 to 100 times). Therefore, by using this method, it is possible to obtain good quality Raman signals that enable more detailed information of species with small Raman cross sections to be obtained.