Electrochemical Promotion of NO Reduction by Hydrogen on a Platinum/Polybenzimidazole Catalyst

Abstract

The electrochemical promotion of catalytic NO reduction by hydrogen was studied using a NO, H 2 , Ar, Pt polybenzimidazole (PBI)-H 3 PO 4 Pt, (H 2 , Ar fuel cell at 135C. A mixture of NO/H 2 /Ar was used as the working mixture at one electrode and a mixture of H 2 /Ar was used as reference and counter gas at the other electrode. Products of NO reduction (N 2 and H 2 O) were analyzed by an on-line mass spectrometer. At high NO H 2 Ar flow rate 17 mL/min; 17 and 354 mL/min, respectively, at atmospheric pressure the maximum rate enhancement ratio was 4.65. At low NO H 2 Ar flow rate 17 mL/min; 17 and 140 mL/min, respectively, NO reduction increased 20 times even without polarization compared to the high gas flow rate. The electrochemical promotion effect occurs at positive polarization with a maximum increase at approximately 0.08 V and with 1.5 times the zero polarization value. The promotion at the negative polarization can be attributed to the electrochemical production of the promoters. At low gas flow rates, a charge-induced change of the strength of chemisorptive bonds can take place.