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Enhancement of the photocatalytic activity of water splitting on 5–30 nm Au nanoparticles/TiO2 nanotube arrays was demonstrated.

Platinum-based bimetallic catalysts exhibit surface atomic rearrangement in various adsorbate environments, which significantly impacts catalysis. A molecular-level understanding of intermediate structures created during catalysis is essential for developing high-performance bimetal catalysts. We show that intermediate Pt−NiO 1−x interfacial structures drive the catalytic synergistic effect observed on Pt 3 Ni nanocrystals. Real-time microscopic observations at ambient pressure show the formation of oxygen-driven Ni oxide clusters on the surface and provide direct evidence of Pt−NiO 1−x interfacial structure formation. Spectroscopic analysis, including ambient-pressure X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy, and catalytic measurements elucidate the role of Pt−NiO 1−x interfacial structures and the catalytic reaction mechanism in CO oxidation. Our results indicate that metal-oxide interfacial intermediate structures in bimetal catalysts relate to the catalytic enhancement of the strong metal−support interaction (SMSI) effect.

The lubricating properties of water have been discussed extensively for millennia. Water films can exhibit high friction in the form of cold ice, or act as lubricants in skating and skiing when liquid. At the fundamental level, friction is the result of a balance between the rate of energy generation by phonon excitation during sliding, and drainage of the energy from the interface by coupling with bulk atoms. Using atomic force microscopy (AFM) we found that when H 2 O water intercalates between graphene and mica it increases the friction between the tip and the substrate, dependent on the thickness of water and graphene layers, while the magnitude of friction increase was reduced by D 2 O water intercalation. With the help of first-principles densityfunctional theory calculations we explain this unexpected behavior by the increased spectral range of vibration modes of graphene caused by water, and by the better overlap of the graphene vibration modes with the mica phonons, which favors more efficient dissipation of the energy. The larger increase in friction with H 2 O vs D 2 O shows that the high-frequency vibration modes of water molecules play a very important role in the transfer of the vibrational energy of the graphene to the phonon bath of the substrate.