Influence of polyoxometallate on oxidation state of tin in Pt/Sn nanoparticles and its importance during electrocatalytic oxidation of ethanol – Combined electrochemical and XPS study

Unsupported Pt/Sn nanoparticles, that had been prepared via polyol method, were modified with ultra-thin (monolayer-type) films of Keggin heteropolyacids of molybdenum and tungsten. The resulting nanostructured catalysts were investigated using both electrochemical and spectroscopic (XPS) methods. Modification of unsupported Pt/Sn with phosphotungstates or phosphomolybdates led to the improvement of the system’s electrocatalytic activity in terms of relatively higher currents observed during oxidation of ethanol, especially when they were recorded and compared at such low potentials as 0.2 or 0.3 V vs. RHE. It can be concluded from the XPS spectroscopic analysis that, following modification with polyoxometallate, the oxidation state of tin has changed. An attempt was also made to distinguish and correlate distinct oxidation states of tin with the system’s overall electrocatalytic activity and to explain the observed enhancement effect during ethanol electrooxidation.

► Unsupported Pt/Sn catalytic nanoparticles have been synthesized for ethanol electrooxidation.
► Modification of Pt/Sn with polyoxometallates has led to enhancement of the catalytic activity.
► Application of polytungstates and polymolybdates induces different catalytic reactivities.
► Enhancement of the catalytic activity has been correlated with changes of the oxidation state of tin component in Pt/Sn.