ChemInform Abstract: Kinetics and Mechanism of “Reduced CO2” Electrooxidation on Electrodispersed Platinum in Different Acid Solutions.

Abstract

017ChemInform Abstract The electrooxidation of CO2 electroadsorbates on electrodispersed Pt electrodes is studied in 0.05 M and 1 M HClO4, 0.5 M H2SO4, and 1 M H3PO4 by means of voltammetric and potential step techniques. The electrooxidation is found to involve three distinguishable processes. The initial first order triggering process is rather insensitive to changes in the solution composition, while the two second order surface processes are significantly influenced by the solution composition. The second order mechanism involves two different "reduced CO2" electroadsorbates that react independently with OH species adsorbed at bare Pt sites. The adsorbates imply anion-H2O-CO2-H bonding interaction and, therefore, an interaction term has to be included in the rate equations to account for the experimental results.

Comparative electrochemical behaviour of CO2 on Pt and Rh electrodes in acid solution

“…As reported in previous publications [6,7], r-CO 2 adsorbates on Pt in acids are formed in the range 0 V _< E _< 0.4 V which is related to the formation of H-adatoms (region I). The voltammogram for the electro-oxidation of r-CO 2 on pc-and cs-Pt electrodes in aqueous 0.5 M H2SO 4 exhibits a complex current peak which is scarcely sensitive to the we topography (Fig.…”

“…For r-CO e electro-oxidation on pc-Rh the value of Ep also depends on Ead (Figs. 5 and 6), and from the corresponding values of qox it results that the largest Oco e appears when E,d =--0.14 V and tad =300 S. These results are in contrast with those already reported for Pt, where the largest value of Oco: was found for E~a = 0.1 V [7].…”

“…Pt and Rh are active electrocatalysts for a number of reactions in aqueous and non-aqueous solutions, but they differ in their behaviour for H-atom electrosorption, and CO 2 electroreduction and electro-oxidation [5][6][7][8][9]. These differences can be related to the fact that Rh catalysts are very active for the selective synthesis of a number of organic compounds from CO and H 2 [10,11].…”

Comparative EQCM study on electrooxidation of carbon oxides adsorption products on noble metals and their alloys. Polycrystalline Pd-based systems

“…The authors generally agree on the presence of linearly and bridge bonded CO species on Pt surface after CO 2 electrosorption [25,[27][28][29]36,38,48,[50][51][52][53][56][57][58][59], together with possible other adsorbates like COH [28,38,40,45], CHO [43] and COOH species [25,28,[30][31][32][33]41,47,50,59]. It was also postulated that CO 2 molecules only block hydrogen atoms, becoming blocked itself by water molecules and anions [26,44,46,51]. In the case of Rh electrode the adsorption product of CO 2 reduction is regarded as generally more reduced than on Pt [34,35,37,52,54].…”

“…The process of CO 2 electrosorption on Pt and Rh depends on such factors as: potential and time of adsorption [28][29][30][31][32][33][34][35][38][39][40]45,46,[50][51][52][53][54][55]58,59], electrode surface morphology [41,51,55], method of electrode pretreatment [51,55] and solution composition [39,46,51,53,54] as well as plane orientation for single crystal electrodes [73][74][75][76][77][78]. The results of earlier experiments performed on noble metal alloys [6,[79][80][81][82][83][84] have showed that in general the surface coverage, structure and composition of the adsorption product are dependent on the alloy surface composition.…”