A Quantitative Examination of Catalyst Component Impacts on Hydrogen Adsorption and Spillover

Hydrogen spillover is a widely recognized but poorly understood surface phenomenon. We coupled volumetric chemisorption with Fourier transform infrared spectroscopy, thermogravimetric analysis, and acid-base titrations to quantify the roles of metal (Pt, Au) and support chemistry (anatase, rutile, P25 titania) on spillover. We show that metal identity has little to no impact on the amount of spillover hydrogen. Spillover pressure dependence is essentially the same on Au/TiO2 and Pt/TiO2, indicating H2 adsorption is equilibrated across both the metal and support. Conversely, spillover is highly sensitive to support surface chemistry, as rutile TiO2 stabilizes ∼5× more surface hydrogen than anatase TiO2. This change is due to a combination of factors, including the rutile surface's higher proton affinity, stabilized surface electronic states, and larger surface entropy. This work highlights the utility of Au/MOx catalysts as control materials for spillover, as they enable quantitative evaluation of H2 adsorption on active metals and spillover onto the support.