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, H2, Ar), Pt polybenzimidazole false(PBIfalse)­H3PO4|normalPt, false(H2, Ar) fuel cell at 135°C. A mixture of NO/H2/normalAr was used as the working mixture at one electrode and a mixture of H2/normalAr was used as reference and counter gas at the other electrode. Products of NO reduction false(N2 and H2Ofalse) were analyzed by an on-line mass spectrometer. At high NO+H2+normalAr 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+H2+normalAr 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. © 2003 The Electrochemical Society. All rights reserved.

Catalytic Reduction of NO by Methane Using a Pt∕C∕polybenzimidazole∕Pt∕C Fuel Cell

“…3 shows that there are electroreduction processes both in the case of the methane conversion drop in the beginning of the polarization and in the case of the promotion of the catalytic reaction. The latter takes place in the same voltage area as the EP effect in our previous study on the methane catalytic oxidation by oxygen 5 and the NO reduction with hydrogen 6 in the PBI fuel cell. It was assumed in our previous papers that these two reactions were promoted by electrochemically produced hydrogen.…”

“…In our previous study on the electrochemical promotion of the catalytic NO reduction by hydrogen in the ͑NO, H 2 , Ar͒, Pt͉PBI͉Pt, ͑H 2 , Ar͒ fuel cell at 135°C, 6 we have found that NO was reduced to N 2 . It has been shown that electrochemical promotion is possible for this reaction.…”

“…Particular methane would be convenient because the development of natural gas-powered vehicles will require the development of more active catalysts to remove N x O y from the exhaust. [1][2][3] The present work is a continuation of our research in the fields of electrochemical promotion [4][5][6] and fuel cells, first the phosphoric acid fuel cells 7 and in the last ten years the polybenzimidazole ͑PBI͒-phosphoric acid fuel cells. 8 The latter have a combination of advantages obtained from polymeric electrolyte fuel cells and phosphoric acid fuel cells, especially the ability to work at temperatures up to 200°C, i.e., elimination of the problem of CO poisoning of the Pt catalyst.…”

“…This case was named the electrochemical production of promoters ͑EPP͒. 6 The difference between EPP and electrocatalysis is that in the latter the products of the catalytic reaction ͑⌳ ഛ 1͒ are electrochemically produced and in the former the promoters of the catalytic reaction are electrochemically produced ͑⌳ ӷ 1͒. The classic example of this EPP case is an electrochemical production of sodium from the Na + ions in ␤Љ-Al 2 O 3 catalyst support.…”

“…The classic example of this EPP case is an electrochemical production of sodium from the Na + ions in ␤Љ-Al 2 O 3 catalyst support. [19][20][21] Electrochemically produced oxygen 12 and hydrogen 5,6 can also be considered as promoters. In the studies of an electrochemical promotion of the catalytic NO reduction by propene at 375°C, Na was pumped to the surface of the catalyst using electrochemical reduction of Na + ions from Na ␤Љ-alumina support.…”