Electrochemical promotion of an oxidation reaction using a proton conductor

摘要

A proton conductor, Ba{sub}3Ca{sub}1.18Nb{sub}1.822O{sub}(9-α)s has been used to electrochemically promote, via potential-controlled spillover of protons, a Pt catalyst-electrode for the model reaction of ethene oxidation at temperature 250-350℃. The rate enhancement is up to 12 times that of the open-circuit rate and typically 10{sup}3 times larger than the rate of proton supply to the catalyst. At the highest temperatures and most oxidizing conditions employed an up to threefold permanent electrochemical enhancement in catalytic rate was also observed. In situ a.c. impedance spectra reveal a buildup of sacrificial promoter, most likely OH formed by reaction of spillover protons with chemisorbed oxygen, under electrochemical promotion conditions. The observed pronounced electrophilic ({partial deriv}r/{partial deriv}U <0) behavior, in conjunction with the reaction kinetics, is in good agreement with the recently established rules of electrochemical and classical promotion.