Effect of Sn_xPt_y Alloy Structures in SnPt Bimetallic Nanoparticle Catalysts on Catalytic Activity for Hydrogenation of Acetic Acid

Abstract

This paper reports on monometallic Pt nanoparticle (Pt-NP) and bimetallic SnPt nanoparticle (SnPt-NP) catalysts with different Sn_xPt_y alloy structures. The catalysts were fabricated using a polyalcohol reduction process, and the catalytic activity of each alloy phase for the hydrogenation of acetic acid to ethanol was investigated. High-resolution transmission electron microscopy (HR-TEM) results confirmed that SnPt-NP catalysts with different Sn/Pt atomic ratios can be successfully synthesized by controlling the Sn/Pt atomic ratios of each metal precursor (platinum(II) acetylacetonate and tin(II) acetate) in the starting mixture during a polyalcohol reduction process. Analyses by inductively coupled plasma spectroscopy and X-ray diffraction (XRD) indicated the formation of uniform Sn₁Pt₃ and Sn₁Pt₁ alloy structures in the SnPt at Sn/Pt atomic ratios of 0.32 and 1.09, respectively. Compared with the monometallic Pt metal phase in the Pt-NP catalysts, the Sn₁Pt₃ alloy phase markedly accelerated the hydrogenation of acetic acid. However, hydrogenation of acetic acid was not observed over the SnPt-NP catalysts at Sn/Pt=1.09, suggesting that the Sn₁Pt₁ alloy phase is inactive for the hydrogenation of carboxylic acids to corresponding alcohols. Therefore, we conclude that the Sn₁Pt₃ alloy phase is the most effective bimetallic SnPt alloy phase for catalyzing the hydrogenation of carboxylic acids.