Bottom-Up Construction of Mesoporous Cerium-Doped Titania with Stably Dispersed Pt Nanocluster for Efficient Hydrogen...

Hydrogen generation is one of the crucial technologies to realize sustainable energy development, and the design of advanced catalysts with efficient interfacial sites and fast mass transfer is significant for hydrogen evolution. Herein, an in situ coassembly strategy was proposed to engineer a cerium-doped ordered mesoporous titanium oxide (mpCe/TiO₂), of which the abundant oxygen vacancies (O) and highly exposed active pore walls contribute to good stability of ultrasmall Pt nanoclusters (NCs, ∼ 1.0 nm in diameter) anchored in the uniform mesopores (ca. 20 nm). Consequently, the tailored mpCe/TiO₂ with 0.5 mol % Ce-doping-supported Pt NCs (Pt-mpCe/TiO₂-0.5) exhibits superior H₂ evolution performance toward the water-gas shift reaction with a 0.73 mol_H2·s^-1·mol_Pt^-1 H₂ evolution rate at 200 °C, which is almost 6-fold higher than the Pt-mpTiO₂ (0.13 mol_H2·s^-1·mol_Pt^-1 H₂). Density functional theory calculations confirm that the structure of Ce-doped TiO₂ with Ce coordinated to six O atoms by substituting Ti atoms is thermodynamically favorable without the deformation of Ti-O bonds. The O generated by the six O atom-coordinated Ce doping is highly active for H₂O dissociation with an energy barrier of 2.18 eV, which is obviously lower than the 2.37 eV for the control TiO₂. In comparison with TiO₂, the resultant Ce/TiO₂ support acts as a superior electron acceptor for Pt NCs and causes electron deficiency at the Pt/support interface with a 0.17 eV downshift of the Pt d-band center, showing extremely obvious electronic metal-support interaction (EMSI). As a result, abundant and hyperactive Ti³⁺-O(-Ce³⁺)-Pt^δ+ interfacial sites are formed to significantly promote the generation of CO₂ and H₂ evolution. In addition, the stronger EMSI between Pt NCs and mpCe/TiO₂-0.5 than that between Pt and mpTiO₂ contributes to the superior self-enhanced catalytic performance during the cyclic test, where the CO conversion at 200 °C increases from 72% for the fresh catalyst to 99% for the used one. These findings reveal the subtle relationship between the mesoporous metal oxide-metal composite catalysts with unique chemical microenvironments and their catalytic performance, which is expected to inspire the design of efficient heterogeneous catalysts.