Proton-exchange-membrane fuel cells (PEMFCs) are attractive next-generation power sources for use in vehicles and other applications1, with development efforts focusing on improving the catalyst system of the fuel cell. One problem is catalyst poisoning by impurity gases such as carbon monoxide (CO), which typically comprises about one per cent of hydrogen fuel2,3,4. A possible solution is on-board hydrogen purification, which involves preferential oxidation of CO in hydrogen (PROX)3,4,5,6,7. However, this approach is challenging8,9,10,11,12,13,14,15 because the catalyst needs to be active and selective towards CO oxidation over a broad range of low temperatures so that CO is efficiently removed (to below 50 parts per million) during continuous PEMFC operation (at about 353 kelvin) and, in the case of automotive fuel cells, during frequent cold-start periods. Here we show that atomically dispersed iron hydroxide, selectively deposited on silica-supported platinum (Pt) nanoparticles, enables complete and 100 per cent selective CO removal through the PROX reaction over the broad temperature range of 198 to 380 kelvin. We find that the mass-specific activity of this system is about 30 times higher than that of more conventional catalysts consisting of Pt on iron oxide supports. In situ X-ray absorption fine-structure measurements reveal that most of the iron hydroxide exists as Fe1(OH)x clusters anchored on the Pt nanoparticles, with density functional theory calculations indicating that Fe1(OH)x–Pt single interfacial sites can readily react with CO and facilitate oxygen activation. These findings suggest that in addition to strategies that target oxide-supported precious-metal nanoparticles or isolated metal atoms, the deposition of isolated transition-metal complexes offers new ways of designing highly active metal catalysts.
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This work was supported by the National Natural Science Foundation of China (grants 21673215, 21533007, 21688102, 91421313, 21473169, U1632263, 11874334 and 51402283); the National Key Research and Development Program of China (grants 2017YFA0402800 and 2016YFA0200600); the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (grant 11621063); the Knut and Alice Wallenberg Foundation (grant 2012.0321); the Swedish Research Council (VR; grant 2015-04062); and the One Thousand Young Talents Program under the Recruitment Program of Global Experts. The calculations were performed on the supercomputing system of the Supercomputing Center of the University of Science and Technology of China. The authors also thank the staff at the 1W1B beamline at the Beijing Synchrotron Radiation Facility (BSRF), the BL14W1 beamline at the Shanghai Synchrotron Radiation Facility (SSRF), the BL12B-a and BL10B beamlines at the National Synchrotron Radiation Laboratory (NSRL), China, and the beamline I311 at the MAX-laboratory, Sweden.
Nature thanks J. Liu and the other anonymous reviewer(s) for their contribution to the peer review of this work.