Divergent catalytic behaviors of Pt and Pd films in the cathode of a sandwiched type membrane reactor

Relative electrochemical and catalytic hydrogenation responses to NO3- reduction by the Ag modified Pt, Pd and Pt-Pd cathodes, deposited on H+ conducting Nafion membrane, have been studied. The electrochemical investigations noticed the maximum reactivity to show by an Ag-Pt electrode exhibiting a reduction current of 24.26 mA cm(-2) at -1.26 V vs. Ag/AgCl reference electrode. Conversely, the catalytic hydrogenation reaction exhibited maximum nitrate reduction rate by an Ag-Pd catalyst having a rate constant of 25.1 x 10(-3) min(-1). While both electrochemical reactions and catalytic hydrogenation reactions were combined in the electrolyte reactor, the highest reduction efficiency was found to show by an Ag-Pt-Pd cathode assembly, where the reduction current was 20.12 mA cm(-2) and the rate constant was 84.3 x 10(-3) min(-1) under controlled current electrolysis condition. In this paper, reasons of such divergent catalytic behaviors have been discussed. (C) 2011 Elsevier B.V. All rights reserved.