Alayoglu Selim, Nilekar Anand U, Mavrikakis Manos, Eichhorn Bryan
Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Nat Mater. 2008 Apr;7(4):333-8. doi: 10.1038/nmat2156. Epub 2008 Mar 16.
Most of the world's hydrogen supply is currently obtained by reforming hydrocarbons. 'Reformate' hydrogen contains significant quantities of CO that poison current hydrogen fuel-cell devices. Catalysts are needed to remove CO from hydrogen through selective oxidation. Here, we report first-principles-guided synthesis of a nanoparticle catalyst comprising a Ru core covered with an approximately 1-2-monolayer-thick shell of Pt atoms. The distinct catalytic properties of these well-characterized core-shell nanoparticles were demonstrated for preferential CO oxidation in hydrogen feeds and subsequent hydrogen light-off. For H2 streams containing 1,000 p.p.m. CO, H2 light-off is complete by 30 (composite function)C, which is significantly better than for traditional PtRu nano-alloys (85 (composite function)C), monometallic mixtures of nanoparticles (93 (composite function)C) and pure Pt particles (170 ( composite function)C). Density functional theory studies suggest that the enhanced catalytic activity for the core-shell nanoparticle originates from a combination of an increased availability of CO-free Pt surface sites on the Ru@Pt nanoparticles and a hydrogen-mediated low-temperature CO oxidation process that is clearly distinct from the traditional bifunctional CO oxidation mechanism.
目前，世界上大部分氢气供应是通过烃类重整获得的。“重整产物”氢气含有大量会使当前氢燃料电池装置中毒的一氧化碳。需要催化剂通过选择性氧化从氢气中去除一氧化碳。在此，我们报告了一种纳米颗粒催化剂的第一性原理指导合成方法，该催化剂由一个钌核和一层约1 - 2个单层厚的铂原子壳层组成。这些表征良好的核壳纳米颗粒在氢气进料中的优先一氧化碳氧化以及随后的氢气起燃方面表现出独特的催化性能。对于含有1000 ppm一氧化碳的氢气流，在30（复合函数）℃时氢气完全起燃，这明显优于传统的铂钌纳米合金（85（复合函数）℃）、纳米颗粒的单金属混合物（93（复合函数）℃）和纯铂颗粒（170（复合函数）℃）。密度泛函理论研究表明，核壳纳米颗粒催化活性增强源于钌@铂纳米颗粒上无一氧化碳的铂表面位点可用性增加以及一个与传统双功能一氧化碳氧化机制明显不同的氢介导低温一氧化碳氧化过程的结合。
