461298 Engineering Core-Shell Nanoparticles of Noble Metals on Transition Metal Carbides As Next-Generation Catalysts in Energy Applications

Thursday, November 17, 2016: 3:55 PM
Imperial B (Hilton San Francisco Union Square)
Maria Milina, Sean T. Hunt, Christopher H. Hendon and Yuriy Román-Leshkov, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Noble metal (NM) catalysts critically enable many existing and emerging technologies, such as catalytic converters, reforming, and fuel cells. However, their scarcity and high cost necessitate the development of catalytic systems with significantly reduced NM loadings, increased activity, and improved durability. Here we present a new class of catalysts based on the transition metal carbide nanoparticles coated with atomically-thin noble metal monolayers. The core-shell structure of the catalysts was attained through a high-temperature self-assembly method by carburizing mixtures of noble metal salts and transition metal oxides encapsulated in removable silica templates. While the materials synthesis was guided by computational quantum chemistry, advanced spectroscopic techniques were applied to corroborate the exact architecture of resulting nanoformulations. The developed synthesis method allowed for precise control of the final nanoparticle architecture, including particle size, monolayer coverage, and heterometallic composition.

Exceptional catalytic performance of the core-shell catalysts was demonstrated in a number of thermo- and electrocatalytic reactions. Carbon-supported tungsten carbide nanoparticles coated with Pt or bimetallic PtRu monolayers exhibited enhanced resistance to sintering and CO poisoning, achieving an order of magnitude increase in specific activity over commercial catalysts for methanol electrooxidation after 10,000 cycles. Moreover, sub-monolayer Pt coverages were able to activate tungsten carbide nanoparticles for hydrogen evolution at low overpotentials and impart hydrogen oxidation activity. The developed catalysts also demonstrated remarkable sinter resistance, and the core-shell structure remained stable at high temperatures under various atmospheres. Collectively, these core-shell catalysts present a novel platform to drastically enhance utilization of noble metals while substantially enhancing their reactivity and stability.

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