Understanding the electrocatalytic activity of PtxSny in direct ethanol fuel cells

In the present work, the activity of PtxSny/C catalysts towards ethanol, acetaldehyde and acetic acid electrooxidation reactions is investigated for each one separately by means of cyclic voltammetry. To this purpose, a series of PtxSny/C catalysts with different atomic ratio (x:y = 2:1, 3:2, 1:1) and small particle size (∼3 nm) are fast synthesized by using the pulse microwave assisted polyol method. The catalysts are well dispersed over the carbon support based on the physicochemical characterization by means of XRD and TEM. Concerning the ethanol electrooxidation, it is found that the Sn addition strongly enhances Pt's electrocatalytic activity and the contributing effect of Sn depends on: (i) the Sn content and (ii) the operating temperature. More precisely, at lower temperatures, Sn-rich catalysts exhibit better ethanol electrooxidation performance while at higher temperatures Sn-poor catalysts give better performance. In the case of acetaldehyde electrooxidation, Pt1Sn 1/C catalyst exhibits the highest activity at all the investigated temperatures; due to the role of Sn, which could effectively remove C 2 species and inhibit the poison formation by supplying oxygen-containing species. Finally, it is found that the PtxSn y/C catalysts are almost inactive (little current was measured) towards the acetic acid electrooxidation. The above findings indicate that Sn cannot substantially promote the electrooxidation of acetic acid to C 1 species. © 2011 Elsevier B.V