Efficient separation of photogenerated electrons and holes, and associated surface reactions, is a crucial aspect of efficient semiconductor photocatalytic systems employed for photocatalytic hydrogen production. A new CoO /TiO /Pt photocatalyst produced by template-assisted atomic layer deposition is reported for photocatalytic hydrogen production on Pt and CoO dual cocatalysts. Pt nanoclusters acting as electron collectors and active sites for the reduction reaction are deposited on the inner surface of porous TiO nanotubes, while CoO nanoclusters acting as hole collectors and active sites for oxidation reaction are deposited on the outer surface of porous TiO nanotubes. A CoO /TiO /Pt photocatalyst, comprising ultra-low concentrations of noble Pt (0.046 wt %) and CoO (0.019 wt %) deposited simultaneously with one atomic layer deposition cycle, achieves remarkably high photocatalytic efficiency (275.9 μmol h ), which is nearly five times as high as that of pristine TiO nanotubes (56.5 μmol h ). The highly dispersed Pt and CoO nanoclusters, porous structure of TiO nanotubes with large specific surface area, and the synergetic effect of the spatially separated Pt and CoO dual cocatalysts contribute to the excellent photocatalytic activity.

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Ideal heterogeneous tandem catalysts necessitate the rational design and integration of collaborative active sites. Herein, we report on the synthesis of a new tandem catalyst with multiple metal-oxide interfaces based on a tube-in-tube nanostructure using template-assisted atomic layer deposition, in which Ni nanoparticles are supported on the outer surface of the inner Al2 O3 nanotube (Ni/Al2 O3 interface) and Pt nanoparticles are attached to the inner surface of the outer TiO2 nanotube (Pt/TiO2 interface). The tandem catalyst shows remarkably high catalytic efficiency in nitrobenzene hydrogenation over Pt/TiO2 interface with hydrogen formed in situ by the decomposition of hydrazine hydrate over Ni/Al2 O3 interface. This can be ascribed to the synergy effect of the two interfaces and the confined nanospace favoring the instant transfer of intermediates. The tube-in-tube tandem catalyst with multiple metal-oxide interfaces represents a new concept for the design of highly efficient and multifunctional nanocatalysts.

The tailoring of metal–oxide interfaces is a powerful approach to enhance the catalytic efficiency of heterogeneous catalysts. However, the function of the metal–oxide interface is still not clearly understood in most catalytic processes. The construction of heterogeneous catalysts with single interface sites would be a straightforward way to reveal the interface effect. In this work, we introduced a simple strategy to synthesize a porous TiO2/Pt/TiO2 sandwich catalyst by atomic layer deposition. All Pt nanoparticles were covered by two porous TiO2 layers in this sandwich structure, creating dominant Pt–TiO2 interface sites. The TiO2/Pt/TiO2 sandwich catalyst shows good catalytic performance in the tandem ammonia–borane decomposition and semihydrogenation of various alkynes with high selectivity and stability. In contrast, the Pt nanoparticles without complete coverage of porous TiO2 layers have a low selectivity in semihydrogenation of alkynes. The sandwich catalyst also exhibits high selectivity in hydrogenation of the −CO bond of α,β-unsaturated aldehyde. The high selectivity of the TiO2/Pt/TiO2 sandwich catalyst can be ascribed to the electron-rich property of the Pt–TiO2 interface sites, which favor the adsorption of alkyne with electrophilicity but inhibit the overhydrogenation of CC bonds.

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