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Photocatalytic CO2 reduction on metal-oxide-based catalysts is promising for solving the energy and environmental crises faced by mankind. The oxygen vacancy （Vo） on metal oxides is expected to be a key factor affecting the efficiency of photocatalytic CO2 reduction on metal-oxide-based catalysts. Yet, to date, the question of how an Vo influences photocatalytic CO2 reduction is still unanswered. Herein, we report that, on Vo-rich gallium oxide coated with Pt nanoparticles （Vo-rich Pt/Ga203）, CO2 is photocatalytically reduced to CO, with a highly enhanced CO evolution rate （21.0umol.h-1） compared to those on Vo-poor Pt/Ga2O3 （3.9 gmol-h-1） and Pt/TiO2（P25） （6.7 gmol.h-1）. We demonstrate that the Vo leads to improved CO2 adsorption and separation of the photoinduced charges on Pt/Ga203, thus enhancing the photocatalytic activity of Pt/Ga203. Rational fabrication of an Vo is thereby an attractive strategy for developing efficient catalysts for photocatalytic CO2 reduction.

Sandwich-style memristor devices were synthesized by electrochemical deposition with a ZnO film serving as the active layer between Al-doped ZnO （AZO） and Au electrodes. The carrier concentration of the ZnO films is controlled by adding HNO3 during the growth process. A resulting increase in carrier concentration from 10^17 to 10^19 cm^-3 was observed, along with a corresponding drop in the on--off ratio from 6,437% to 100%. The resistive switching characteristics completely disappeared when the carrier concentration was above 1029 cm-3, making it unsuitable for a memory device. The decreasing switching ratio is attributed to a reduction in the driving force for oxygen vacancy drift. Systematic analysis of the migration of oxygen vacancies is presented, including the concentration gradient and electrical potential gradient. Such oxygen vacancy migration dynamics provide insight into the mechanisms of the oxygen vacancy drift and provide valuable information for industrial production of memristor devices.

The charge-trapping process, with HfO2 film as the charge-capturing layer, has been investigated by using in situ electron energy-loss spectroscopy and in situ energy-filter image under positive external bias. The results show that oxygen vacancies are non-uniformly distributed throughout the HfO2 trapping layer during the programming process. The distribution of the oxygen vacancies is not the same as that of the reported locations of the trapped electrons, implying that the trapping process is more complex. These bias-induced oxygen defects may affect the device performance characteristics such as the device lifetime. This phenomenon should be considered in the models of trapping processes.

CO2 photoreduction by semiconductors is of growing interest. Fabrication of oxygen-deficient surfaces is an important strategy for enhancing CO2 photoreduction activity. However, regeneration of the oxygen vacancies in photocatalysts is still a problem since an oxygen vacancy will be filled up by the O atom from CO2 after the dissociation process. Herein, we have fabricated highly efficient BiOC1 nanoplates with photoinduced oxygen vacancies. Oxygen vacancies were easily regenerated by light irradiation due to the high oxygen atom density and low Bi~） bond energy even when the oxygen vacancies had been filled up by the O atom in the photocatalytic reactions. These oxygen vacancies not only enhanced the trapping capability for CO2, but also enhanced the efficiency of separation of electron-hole pairs, which resulted in the photocatalytic CO2 reduction under simulated solar light. Furthermore, the generation and recovery of the defects in the BiOC1 could be realized during the photocatalytic reduction of CO2 in water. The existence of photoinduced defects in thin BiOC1 nanoplates undoubtedly leads to new possibilities for the design of solar-driven bismuth based photocatalysts.

We investigated the effects of oxygen vacancies on the structural, magnetic, and transport properties of Lal-xSrxMnO3 （x=0.1, 0.2, 0.33, 0.4, and 0.5） grown around a critical point （without/with oxygen vacancies） under low oxygen pressure （10 Pa） and high oxygen pressure （40 Pa）. We found that all films exhibit ferromagnetic behavior below the magnetic critical temperature, and that the films grown under low oxygen pressures have degraded magnetic properties with lower Curie temperatures and smaller magnetic moments. These results show that in epitaxial La1-xSrxMnO3 thin films, the magnetic and transport properties are very sensitive to doping concentration and oxygen vacancies. Phase diagrams of the films based on the doping concentration and oxygen vacancies were plotted and discussed.

Oxygen vacancy, a kind of native point defects in ferroelectric ceramics, usually causes an increase of the dielectric loss. Based on experimental observations, it is believed that all of the oxygen vacancies are an unfavorable factor for energy saving. By using molecular dynamics simulations, we show that the increase of coercive and saturated electric fields is due to the dif- ficulty to switch local polarization near an oxygen vacancy, and so that a ferroelectric device has to sustain the rising con- sumption of energy. The simulation results also uncover how oxygen vacancies influence ferroelectric properties.

Using first-principle theory, the infrared absorptions of transition metal （Mn, Fe, Co, Ni）-doped ZnO were investigated. The results indicate that the absorptions of Mn- and Co-incorporated ZnO without oxygen vacancy are reduced, while those of Fe- and Ni-doped ZnO are raised. This is consistent with the previous experimental results. The effects of oxygen vacancy on the absorptions of the doped systems were predicted. When a neutral oxygen vacancy is introduced, all doping elements decrease the absorptions. On the contrary, the absorptions of the doped systems are enhanced if the vacancies are charged. Degraded absorptions can be obtained by increasing the permeability. However, the appearance of anti-bonding states may cause enhanced absorptions. In the current study, Mn-doped ZnO is the most suitable for use as low infrared absorption materials.