Effects of adsorbate coverage and bond-length disorder on the d-band center of carbon-supported Pt catalysts

Determination of the factors that affect the d-band center of catalysts is required to explain their catalytic properties. Resonant inelastic X-ray scattering (RIXS) enables direct imaging of electronic transitions in the d-band of Pt catalysts in real time and in realistic environmental conditions. Through a combination of in situ, temperature-resolved RIXS measurements and theoretical simulations we isolated and quantified the effects of bond-length disorder and adsorbate coverage (CO and H₂) on the d-band center of 1.25 nm size Pt catalysts supported on carbon. We found that the decrease in adsorbate coverage at elevated temperatures is responsible for the d band shifts towards higher energies relative to the Fermi level, whereas the effect of the increase in bond-length disorder on the d-band center is negligible. Although these results were obtained for a specific case of non-interacting support and weak temperature dependence of the metal-metal bond length in a model catalyst, this work can be extended to a broad range of real catalysts. Don't let disorder bother you: Using resonant inelastic X-ray scattering (RIXS) measurements the changes in the d-band center of carbon-supported Pt nanocatalysts are imaged in response to variable temperatures and gas atmospheres. Theoretical analysis of RIXS data reveals that the d-band-center shift toward the Fermi level at elevated temperatures is dominated by the decrease in adsorbate coverage, whereas the increase of bond-length disorder plays no significant role.