The Role of SnO2 on Electrocatalytic Activity of PtSn Catalysts

In our previous paper, we described in detail studies of Sn influence on electrocatalytic activity of PtSn catalyst for CO and formic acid oxidation (Stevanovic et al., J. Phys. Chem. C, 118 (2014) 278–289). The catalyst was composed of a Pt phase, Pt3Sn alloy and very small SnO2 particles. Different electrochemical treatment enabled studies of PtSn/C having Sn both in surface and subsurface layers and skeleton structure of this catalyst with Sn only in subsurface layers. The results obtained revealed the promotional effect of surface Sn whether alloyed or as oxide above all in preventing accumulation of CO and blocking the surface Pt atoms. As a consequence, in formic acid oxidation, the currents are not entering the plateau but increasing constantly until reaching a maximum. It was concluded that at lower potentials the effect of Sn on formic acid oxidation was predominantly electronic but with increasing the potential bi-functional mechanism prevailed due to the leading role of SnO2. This role of SnO2 is restated in the present study. Therefore, CO and formic acid oxidation were examined at PtSnO2/C catalyst. The catalyst was synthesised by the same microwave-assisted polyol procedure. According to XRD analysis, the catalyst is composed of a Pt phase and SnO2 phase. The reactions were examined on PtSnO2/C catalyst treated on the same way as PtSn/C. Comparing the results obtained, the role of SnO2 is confirmed and at the same time the significance of alloyed Sn and its electronic effect is revealed.