The role of the WO3 nanostructures in the oxygen reduction reaction and PEM fuel cell performance on WO3–Pt/C electrocatalysts

• WO3 nanoparticles generated by chemical reduction were incorporated to Pt/C catalysts.
• XPS results showed the strong interaction between Pt and WO3 at low tungsten content.
• This SMSI was associated with an increased activity in the oxygen reduction reaction.

Oxygen reduction reaction (ORR) was investigated on carbon supported platinum and tungsten oxide nanoparticles generated by chemical reduction. The results were correlated with the surface properties of these electrocatalysts. X-ray Photoelectron Spectroscopy (XPS), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Transmission Electron Microscopy (STEM), Energy Dispersive Spectroscopy (EDS) studies have been used to analyze the structure and surface properties of WO3–Pt/C electrocatalysts. The analysis of the platinum Pt 4f peak by XPS showed that this metal is present in the surface as Pt0 with some oxidized platinum Pt2+, while tungsten oxide is present as W6+. The XPS results showed the strong interaction between Pt and WO3. By electron microscopy techniques, it was observed that using this synthesis method, both, platinum and tungsten oxide are well dispersed on vulcan carbon, which may favor the formation of Pt–WO3 interfaces. Thus, in comparison to conventional Pt/C, the 5%WO3–Pt/C electrocatalyst exhibited higher electrocatalytic activity toward the oxygen reduction reaction in a single cell polymer electrolyte membrane (PEM) fuel cell. However, with the incorporation of tungsten oxide at higher contents the WOx species are more dominating on the catalysts surface, reducing the accessibility of the reactants to the platinum active sites and therefore the electrochemical response in the ORR.