Electrochemical Reduction of Oxygen and Nitric Oxide at Low Temperature on La1xSrxCoO3delta Cathodes

Six La1-xSrxCoO3-δ (x= 0, 0.05, 0.15, 0.25, 0.35, 0.50) perovskites were synthesised and characterised by powder XRD and cyclic voltammetry on cone-shaped electrodes in either air or nitric oxide in argon at 200, 300 and 400C. At 200C the current densities in air was highest for the strontium free cobaltite, whereas the current densities was highest for La0.95Sr0.05CoO3-δ in the nitric oxide containing atmosphere. This was also the compound with the highest INO/IO2 current ratio at 200C. At higher temperatures a limiting cathodic current was observed for all of the cobaltite’s, except La0.50Sr0.50CoO3-δ, in both air and the nitric oxide containing atmosphere. This was attributed to a rate limiting chemical step (i.e. dissociation of oxygen or nitric oxide) in the reaction sequence. Introduction: The formation of nitric oxide in the combustion process in Diesel fired engines is well known [1]. This gives problems with pollution in the form of acid rain. NOx is also harmful to human beings as it can lead to lung oedema [2]. Electrochemical reduction of nitric oxide is a potentially convenient technique to remove NOx from Diesel exhaust gasses [3]. In an electrochemical cell, with an oxide anion-conducting electrolyte, the NOx is reduced to nitrogen and oxide anions at the cathode. The oxide anions are removed from the cathode and are transported through the electrolyte to the anode where oxygen is formed. The main obstacle with this technique is the simultaneously reduction of e‐mail: [email protected]