Preventing Pt Catalysts in PEM Fuel Cells from CO Poisoning by Getting COPROX to Work

Abstract

Proton-exchange membrane fuel cells still require CO-scrubbed H2 feedstreams to sustain long-duration performance. Sufficiently CO-free H2 costs an order of magnitude more than steam refining fossil fuels to generate H2—and until green processes produce the bulk of H2, preferential oxidation of CO from H2-rich feedstreams, also known as COPROX, is a necessity. We design architected catalytic platforms as ultraporous metal nanoparticle–modified oxide aerogels in which a covalently bonded oxide nanoparticulate network (NPs) supports comparably sized catalytic nanoparticles (NPs). The degree of physical and chemical interfacial intimacy stabilizes the more catalytically active low valent state of Cu and the ultraporous catalytic platform demonstrates high activity and on-stream durability for thermal catalysis of CO [1]. We then evaluate the selectivity and activity of this architected catalyst and a related aerogel, Cu/GdxCe1–xO2, for preferential oxidation of CO (COPROX) in H2 feedstreams. The catalysts convert >95% of CO at temperatures that prevent oxidation (consumption) of the H2 fuel (a purification reaction necessary to prevent poisoning of the anode catalysts in H2 fuel cells). The architected Cu/ceria catalysts achieve >95% selectivity vs. H2 and maintain this unprecedented activity for >16 h at 100°C in dry or humidified feedstreams [2,3]. The ability to purify H2 from steam-reformed fuels for use in proton-exchange membrane fuel cells increases power source flexibility as the world transitions to more sustainable, carbon-neutral routes to highly purified H2.[1] Stabilization of reduced copper on ceria aerogels for CO oxidation. C. L. Pitman, A. M. Pennington, T. H. Brintlinger, D. E. Barlow, L. F. Esparraguera, R. M. Stroud, J. J. Pietron, P. A. DeSario, D. R. Rolison, Nanoscale Adv. 2020, 2, 4547–4556 (10.1039/D0NA00594K).[2] Preferential oxidation of CO in H2-containing gas. T.G. Novak, D.R. Rolison, P.A. DeSario, US Patent Application, filed Jan 27, 2023 [Navy Case #210,945].[3] Cu/CeO2 and Cu/Gd-substituted CeO2 aerogels for active, selective, and stable COPROX catalysis. T.G. Novak, P.A. DeSario, T.H. Brintlinger, R.H. DeBlock, J.W. Long, and D.R. Rolison, ACS Sus. Chem. Eng. 2023, 11, 2853–2860 (10.1021/acssuschemeng.2c06158).