Kesong Yang

This work for the first time reports engineered oxygen-deficient, blue TiO2 nanocrystals with coexposed {101}-{001} facets (TiO2–x{001}-{101}) to enhance CO2 photoreduction under visible light. The TiO2–x{001}-{101} material demonstrated a relatively high quantum yield (0.31% under UV–vis light and 0.134% under visible light) for CO2 reduction to CO by water vapor and more than 4 times higher visible light activity in comparison with TiO2 with a single {001} plane or {101} plane and TiO2(P25). Possible reasons are the exposure of more active sites (e.g., undercoordinated Ti atoms and oxygen vacancies), the facilitated electron transfer between {001} and {101} planes, and the formation of a new energy state (Ti3+) within the TiO2 band gap to extend the visible light response. An in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study was applied to understand the roles of coexposed {001}-{101} facets and Ti3+ sites in activating surface intermediates. The in situ DRIFTS analysis suggested that the coexposed {001}-{101} facets increased the capacity of reversible CO2 adsorption and that the combination of {001}-{101} and Ti3+ enhanced the activation and conversion kinetics of adsorbed species. The visible light responsive TiO2–x{001}-{101} material is not oxidized after long-term exposure to an air environment. This work is a significant contribution to the design of efficient and stable solar fuel catalysts.

We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with p type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure.