Probing structure-functionality relationships of catalytic bimetallic Pt–Ru nanoparticles associated with improved sulfur resistance

Abstract

Supported bimetallic Pt–Ru alloyed nanoparticulate catalysts, which show improved sulfur tolerance for a model aqueous phase reforming reaction, were investigated using X-ray absorption spectroscopy (XANES and EXAFS) at the Pt L_III and the Ru K-edges, before and after exposure to thiophene, a sulfur-containing model poison. Preliminary EXAFS investigations confirmed the alloyed character of the bimetallic catalysts, and further experiments allowed us to clearly determine more detailed changes to the Pt–Ru bonding environments as induced by sulfur poisoning, i.e. partial particle dealloying. However, after treating the poisoned catalysts with pure H₂ at 300 °C, the Pt–Ru alloy appeared to regenerate. These results, based on the atomic environments of the absorbing species, are consistent with our previous catalytic and bulk powder X-ray diffractive investigations, and support our proposed sulfur and hydrogen spillover in situ self regeneration mechanism.