Pd As a Reduction Promoter for TiO2: Oxygen and Hydrogen Transport at 2D and 3D Pd Interfaces with TiO2 Monitored by TPR, Operando 1H NMR and CO Oxidation Studies

Ambient temperature reduction of TiO2 surface was observed through hydrogen spillover from Pd nanoparticles with a hydrogen consumption stoichiometry of 1.4 H2:Pd up to ≤2 wt%Pd loading. This behavior was attributed to the formation of nanoparticles exhibiting 2D behavior for ≤2 wt%Pd loading. The 2D behavior of Pd nanoparticles were further confirmed from the relative abundance of metallic Pd in 3D, deduced from hydrogen stoichiometry of β-PdHx. EPR revealed oxygen vacancy formation, operando NMR revealed facile hydrogen spillover, and CO oxidation reaction rates systematically increased for Pd ≤ 2 wt%, indicating facile exchange of hydrogen and oxygen at 2D Pd/TiO2 interfaces.