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Analysis of the selectivity of PtRh/C and PtRhSn/C to the formation of CO2 during ethanol electrooxidation

2013; Elsevier BV; Volume: 112; Linguagem: Inglês

10.1016/j.electacta.2013.09.030

1873-3859

Luiz C. Silva-Júnior, Gilberto Maia, Raimundo Ribeiro Passos, Elson Almeida de Souza, Giuseppe A. Câmara, M. Janete Giz,

CO2 Reduction Techniques and Catalysts

PtRh and PtRhSn electrocatalysts of different atomic compositions were prepared by dispersion on carbon Vulcan XC-72R using the polyol reduction method and characterized by energy dispersive X-ray analysis, X-ray diffraction and transmission electron microscopy. The electrooxidation of ethanol was investigated in acid medium by cyclic voltammetry, chronoamperometry and in situ Fourier transform infrared spectroscopy (FTIR) experiments. Results showed that the electrochemical response in presence of ethanol is strongly influenced by the composition of the catalyst. The in situ FTIR results allowed correlating the electrochemical response with the formation of CO2 and acetic acid and suggest that although there is anticipation in the formation of both species, the presence of Rh is deleterious for the electrocatalytic activity of the binary electrodes (at least for the compositions range investigated), probably due to the slow kinetics of adsorption of ethanol on Rh. Conversely, the ternary catalyst (Pt61Rh09Sn30/C) facilitates both adsorption and oxidation steps which explain the higher currents observed in the voltammetric and chronoamperometric experiments. However, Sn seems not to drive the reaction toward the production of CO2, and the electrocatalysis is better explained by a non-selective oxidation process.