Manipulating Atomic Structures at the Au/TiO2 Interface for O2 Activation.

The metal/oxide interface has been extensively studied due to its importance for heterogeneous catalysis. However, the exact role of interfacial atomic structures in governing catalytic processes still remains elusive. Herein, we demonstrate how the manipulation of atomic structures at the Au/TiO2 interface significantly alters the interfacial electron distribution and prompts O2 activation. It is discovered that at the defect-free Au/TiO2 interface electrons transfer from Ti3+ species into Au nanoparticles (NPs) and further migrate into adsorbed perimeter O2 molecules (i.e., in the form of Au-O-O-Ti), facilitating O2 activation and leading to a ca. 34 times higher CO oxidation activity than that on the oxygen vacancy (Vo)-rich Au/TiO2 interface, at which electrons from Ti3+ species are trapped by interfacial Vo on TiO2 and hardly interact with perimeter O2 molecules. We further reveal that the calcination releases those trapped electrons from interfacial Vo to facilitate O2 activation. Collectively, our results establish an atomic-level description of the underlying mechanism regulating metal/oxide interfaces for the optimization of heterogeneous catalysis.

Surface-Plasmon-Driven Hot Electron Photochemistry.

Visible-light-driven photochemistry has continued to attract heightened interest due to its capacity to efficiently harvest solar energy and its potential to solve the global energy crisis. Plasmonic nanostructures boast broadly tunable optical properties coupled with catalytically active surfaces that offer a unique opportunity for solar photochemistry. Resonant optical excitation of surface plasmons produces energetic hot electrons that can be collected to facilitate chemical reactions. This review sums up recent theoretical and experimental approaches for understanding the underlying photophysical processes in hot electron generation and discusses various electron-transfer models on both plasmonic metal nanostructures and plasmonic metal/semiconductor heterostructures. Following that are highlights of recent examples of plasmon-driven hot electron photochemical reactions within the context of both cases. The review concludes with a discussion about the remaining challenges in the field and future opportunities for addressing the low reaction efficiencies in hot-electron-induced photochemistry.

Experimental Insights into the Growth of Single Truncated Anatase Bipyramids.

Fluorine has been recognized to selectively stabilize anatase titanium dioxide (TiO2 ) crystal facets; however, resolving its physical location at the nanometer scale remains empirically elusive. Here, we provide direct experimental evidence to reveal the spatial distribution of fluorine on single truncated anatase bipyramids (TABs) using nanoscale secondary ion mass spectrometry (NanoSIMS). Fluorine was found to preferentially adsorb on the (001) facet compared to the (101) facet of TABs. Moreover, NanoSIMS depth profiling exhibited a significantly different fluorine distribution between these two facets in the near-surface region, illustrating the essential role of lattice-doped fluorine in the anisotropic crystal growth of TABs.

Elucidating the Origin of Plasmon-Generated Hot Holes in Water Oxidation.

Plasmon-generated hot electrons in metal/oxide heterostructures have been used extensively for driving photochemistry. However, little is known about the origin of plasmon-generated hot holes in promoting photochemical reactions. Herein, we discover that, during the nonradiative plasmon decay, the interband excitation rather than the intraband excitation generates energetic hot holes that enable to drive the water oxidation at the Au/TiO2 interface. Distinct from lukewarm holes via the intraband excitation that only remain on Au, hot holes from the interband excitation are found to be transferred from Au into TiO2 and stabilized by surface oxygen atoms on TiO2, making them available to oxidize adsorbed water molecules. Taken together, our studies provide spectroscopic evidence to clarify the photophysical process for exciting plasmon-generated hot holes, unravel their atomic-level accumulation sites to maintain the strong oxidizing power in metal/oxide heterostructures, and affirm their crucial functions in governing photocatalytic oxidation reactions.