Solid State Ionics 136–137 (2000) 775–782 www.elsevier.com / locate / ssi 9 Electrocatalytic reduction of NO on La AB BO : x 1 2x x 1 2y y 3 2d evidence of electrically enhanced activity a, b b b * Eric D. Wachsman , Palitha Jayaweera , Gopala Krishnan , Angel Sanjurjo a Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611-6400, USA b Materials Research Center, SRI International, Menlo Park, CA 94025, USA Abstract Solid-state electrochemical cells can be used to sense and reduce NO from combustion exhaust gases. In the reduction x process the products are N and O . For these cells to be effective in fuel-lean combustion exhaust, cathode materials with 2 2 9 high selectivity for NO vs. O are necessary. Numerous compositions of La AB BO (where A is Sr or Ba; and B 2 12x x 12y y 32d and B9 are transition metals) were investigated for heterogeneous catalytic activity and selectivity for NO reduction using temperature programmed reaction (TPR). Ceramic cells using these materials as cathodes were fabricated and used to electrocatalytically reduce NO in NO / He and simulated exhaust atmospheres. An enhanced electrocatalytic three-way activity for NO reduction was demonstrated that increases the window of operation into fuel-lean conditions.  2000 x Elsevier Science B.V. All rights reserved. Keywords: NO; Electrocatalysis; NEMCA Materials: NO; La A BO 12x x 3 1. Introduction cathode forming gaseous N and solid-phase oxygen 2 ions: Solid-state electrochemical cells can be used to NO 1 2e91 V → O 1 1/2N (1) dd X O O 2 sense and reduce NO from combustion exhaust x gases. The solid-state electrocatalytic reduction of Gaseous O are evolved at the anode with formation 2 NO to N and O was first demonstrated by Pan- 2 2 of V that are transported through the electrolyte: dd O charatnam et al. [1] and subsequently investigated for combustion emission reduction [2–5]. The con- O → V 1 2e91 1/2O (2) X dd O O 2 cept for this is depicted in Fig. 1. When a small DC potential ( | 1 V) is applied The overall cell reaction is simply the NO decompo- across the cell, NO is directly reduced at the sition reaction: x NO → 1/2N 1 1/2O (3) 2 2 *Corresponding author. Tel.: 11-352-846-2991. E-mail address: ewach@mse.ufl.edu (E.D. Wachsman). For a Faradaic reaction the NO reduction rate, r NO 0167-2738 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0167-2738(00)00548-8