Methanol oxidation over silica-supported Pt and Ag nanoparticles: Toward selective production of hydrogen and carbon dioxide

Abstract

Pt, Ag, and Pt–Ag nanoparticles smaller than 5 nm were synthesized by a simple, alcohol reduction. These and similar materials may have many applications including photocatalysis because of the ability to tune the plasmonic and catalytic properties. After immobilization onto silica, the particles were tested for methanol decomposition and partial methanol oxidation. For methanol decomposition, Ag/silica was the more active than Pt/silica. This result was in agreement with product poisoning (CO) limiting turnover and CO generally binding more weakly to Ag than Pt surfaces. The properties of the bimetallic Pt–Ag were between the parent catalysts, but different than their physical mixture, which indicated Pt–Ag bimetallic formation. The catalytic activity for partial methanol oxidation was greater than methanol decomposition for all catalysts. The Pt/silica catalyst demonstrated the best hydrogen and carbon dioxide yields when oxygen was added. The results are discussed in the discussion of a two-step process in which methanol is decomposed to carbon monoxide and hydrogen and then these species are oxidized to water and carbon dioxide. Further work is needed to refine the process and the catalyst to achieve CO-free hydrogen from methanol and oxygen.