Acetic acid internal reforming in a solid oxide fuel cell-reactor using Cu-CeO_2 anodic composites

摘要

This work targets to explore the performance of Cu-CeO_2 anodes for the production of hydrogen and power generation during the internal steam reforming of CH_3COOH in SOFC reactors. When the cell operated as an electrochemical membrane reactor, the effect of temperature, reactants' partial pressures and imposed overpotentials on the catalytic activity and selectivity of Cu/CeO_2 electrodes, at both open and closed circuit operations, were investigated. The results show that at open circuit conditions, CH_3COOH is efficiently reformed by H_2O to syngas, where the observed products' distribution is influenced by both the associated CH_3COOH thermal/catalytic decomposition reactions and by the reverse water gas shift reaction. In all cases examined, neither acetone nor carbon is observed at the effluents, with the latter being attributed to the gasification of carbonaceous deposits by H_2O to CO and H_2. At anodic polarization conditions, Cu-CeO_2 exhibits high catalytic activity toward the electro-oxidation of all combustible species. Kinetic experiments show that the reaction mechanism involves the dissociative adsorption and decomposition of both reactants on the catalyst surface, where the subsequent interaction of the resulted fragments leads to the observed final products. In the fuel cell mode, the electrochemical performance of Cu-CeO_2 was investigated by voltage-current density-power density and AC impedance measurements. Ohmic losses are the prevailing source of polarization, mainly attributed to the anodic interfacial resistance, which is significantly influenced by cell temperature and reactants composition. The electrode performance is mainly limited by the diffusion of the charged or neutral species to triple phase boundary while in the case of dry feeding mixtures, the charge transfer processes determine the overall efficiency.