New Basal Co <sub> 2 </ Sub> Co Adsorption On Pt Electrochemical Reduction And In Ionic Liquids Study

Small carbon-oxide compounds (CO2 and CO) have attracted for decades broad interests in electrocatalysis investigations for the following two reasons. On one hand, the global concern over the CO2 greenhouse effect has triggered the intense study on the recycled use of CO2 for the sustainable development of future energy. On the other hand, CO is one of the most important prototype adsorbates on metal electrodes for electrocatalysis, relevant to numerous surface reactions including those in the proton exchange membrane fuel cells. This thesis is mainly focused on the reduction process of CO2 on a new form of substrate and the adsorption properties of CO on Pt electrode in an ionic liquid medium by using the electrochemical and spectroscopic techniques, carrying with both fundamental and practical significances.1. Electroreduction of CO2 on electrodeposited RuO2 on TiO2Non-biological techniques for converting CO2 should be adopted as supplements to the policy of "energy-saving and controlled outlet". Electrochemical reduction is one of the promising methods for its mild conditions and the capability to convert CO2 effectively into formic acid, methanol and other small organic molecules as possible fuels.The conductive metallic oxide RuO2 has proved to be an effective material for electrochemical reduction of CO2. Its electrocatalytic activity was enhanced when RuO2 was formed on TiO2 substrate. Normally, the catalyst was prepared through thermal decomposition (TD) of an alcoholic solution containing Ru(III) and Ti(IV). However, the thus-prepared RuO2/TiO2 composites turned out to exhibit low utilization, inhomogeneous dispersion and low activity, preventing their wider applications, calling for a new and effective preparation tactics.In our present work, cyclic voltammetric method has been applied to deposit ultrathin amorphous RuO2 nanolayers uniformly on TiO2 nanoparticles and nanotubes substrates. The as-prepared RuO2/TiO2 composites were used for the electrocatalytic reduction of CO2. As compared to the traditional crystalline RuO2/TiO2 samples prepared by TD, the currently-prepared samples show a positive shift of 100 raV for the initial reduction potential and more than 70%higher reduction current density. Further analysis shows that the content of Ru on this electrode is less than 1/30 of that prepared by TD, HCOOH and CH4 are the main products, and TiO2 nanotubes have more significant coeffect as compared to TiO2 nanoparticles.2. ATR-SEIRAS study of the behavior of CO adsorbed at Pt electrode in ionic liquidThe interfacial behavior of CO adlayer at metal electrodes has been extensively studied in aqueous electrolytes by using infrared spectroscopy. Only a few relevant reports were related to that in non-aqueous electrolytes consisting of salts and organic solvents, but none in room-temperature ionic liquids (RTILs) despite a low-sensitivity SFG measurement focused on the double layer structures of the RTIL/metal interface. RTILs have wide electrochemical windows, high ionic conductivities and simple compositions. On the other hand, surface enhanced IR absorption spectroscopy (SEIRAS) in ATR configuration is a highly sensitive tool for interfacial analysis. According to the effective dielectric medium theory, the SEIRAS enhancement may vary depending on the nature of a medium in which the metallic nanoparticle film is immersed. However, no specific investigation was designed to examine this point.In situ ATR-SEIRAS has been applied to investigate the CO adsorption at Pt electrode in a hydrophobic RTIL, i.e., Pip14TNf2, over the ever-widest stability potential window about 4.1 V. The combined electrochemical and spectroscopic measurements reveal that the Stark tuning rates of COL and COB are distinct at the turning point of ca.-1.0 V, in corroborating with the change of direction of the passing current, indicative of the different interfacial structures across-1.0 V. The gradual conversion of COb to COL over a wider potential range enables a reliable determination of the ratio of apparent adsorption coefficient of COL relative to that of COB (ca.1.22). In addition, a negligible difference in surface IR enhancement is found for CO adlayer at Pt electrode in aqueous 0.1 M HCIO4 and in the above RTIL.