Achieving water-floatable photocatalyst on recycled bamboo chopsticks.

Disposable bamboo chopsticks (DBCs) are difficult to recycle, which inevitably cause secondary pollution. Based on energy and environmental issues, we propose a facile strategy to fabricate floatable photocatalyst (fPC) coated onto DBCs, which can be flexibly used in water purification. The photocatalyst of titania and titanium carbide on bamboo (TiO2/TiC@b) was successfully constructed from TiC-Ti powders and DBCs using a coating technique followed heat treatment in carbon powder, and the fPC exhibited excellent photocatalytic activity under visible light irradation. The analysis results indicate that rutile TiO2 forms on TiC during heat treatment, achieving a low-density material with an average value of approximately 0.5233 g/cm3. The coatings of TiO2/TiC on the bamboo are firm and uniform, with a particle size of about 20-50 nm. XPS results show that a large amount of oxygen vacancies is generated, due to the reaction atmosphere of more carbon and less oxygen, further favoring to narrowing the band gap of TiO2. Furthermore, TiO2 formed on residual TiC would induce the formation of a heterojunction, which effectively inhibits the photogenerated electron-hole recombination via the charge transfer effect. Notably, the degradation of dye Rhodamine B (Rh.B) is 62.4% within 3 h, while a previous adsorption of 36.0% for 1 h. The excellent photocatalytic performance of TiO2/TiC@b can be attributed to the enhanced reaction at the water/air interface due to the reduced light loss in water, improved visible-light response, increased accessible area and charge transfer effect. Our findings show that the proposed strategy achieves a simple, low-cost, and mass-producible method to fabricate fPC onto the used DBCs, which is expected to applied in multiple fields, especially in waste recycling and water treatment.

Oxygen vacancies induced band gap narrowing for efficient visible-light response in carbon-doped TiO2.

The band gap of rutile TiO2 has been narrowed, via the formation of oxygen vacancies (OVs) during heat treatment in carbon powder (cHT) with embedding TiO2 coatings. The narrowed band gap efficiently improves the visible light response of TiO2 coatings, to further enhance the visible-light-driven photocatalytic activity. The change in OVs during cHT has been studied by manipulation of cHT temperature and time. The effect of OVs on the band structure of nonstoichiometric TiO2-x has been further calculated by first-principles calculations. With raising the temperature, SEM images show that the nano-size fiber-like structure forms on the surface of TiO2 coatings, and the amount of the fiber-like structure significantly increases and their size changes from nano to micro under 800 °C, contributing to cause an increase in accessible surface area. The UV-Vis results reveal that the band gap of TiO2 has been narrowed during cHT, due to the formed oxygen vacancies. The XPS results further confirm that the formation of surface defects including OVs, and the XPS depth profile further shows the decreased relative amount of O whereas increased relative amount of carbon. Notably, after cHT for TiO2 coatings, the photocatalytic activity first increases then decreases with raising the temperature, achieving approximately 3 times at 850 °C. The first-principles calculation suggest that the OVs in TiO2 coatings with localized electrons could facilitate the band gap narrowing, further favoring to enhance the photocatalytic activity under visible light.

Inactivation of SARS-CoV-2 and photocatalytic degradation by TiO2 photocatalyst coatings.

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causative agent of the COVID-19, which is a global pandemic, has infected more than 552 million people, and killed more than 6.3 million people. SARS-CoV-2 can be transmitted through airborne route in addition to direct contact and droplet modes, the development of disinfectants that can be applied in working spaces without evacuating people is urgently needed. TiO2 is well known with some features of the purification, antibacterial/sterilization, making it could be developed disinfectants that can be applied in working spaces without evacuating people. Facing the severe epidemic, we expect to fully expand the application of our proposed effective approach of mechanical coating technique (MCT), which can be prepared on a large-scale fabrication of an easy-to-use TiO2/Ti photocatalyst coating, with hope to curb the epidemic. The photocatalytic inactivation of SARS-CoV-2 and influenza virus, and the photocatalytic degradation of acetaldehyde (C2H4O) and formaldehyde (CH2O) has been investigated. XRD and SEM results show that anatase TiO2 successfully coats on the surface of Ti coatings, while the crystal structure of anatase TiO2 can be increased during the following oxidation in air. The catalytic activity towards methylene blue of TiO2/Ti coating balls has been significantly enhanced by the followed oxidation in air, showing a very satisfying photocatalytic degradation of C2H4O and CH2O. Notably, the TiO2/Ti photocatalyst coating balls demonstrate a significant antiviral activity, with a decrease rate of virus reached 99.96% for influenza virus and 99.99% for SARS-CoV-2.

Efficient and Selective Interplay Revealed: CO2 Reduction to CO over ZrO2 by Light with Further Reduction to Methane over Ni0 by Heat Converted from Light.

The reaction mechanism of CO2 photoreduction into methane was elucidated by time-course monitoring of the mass chromatogram, in situ FTIR spectroscopy, and in situ extended X-ray absorption fine structure (EXAFS). Under 13 CO2 , H2 , and UV/Vis light, 13 CH4 was formed at a rate of 0.98 mmol h-1 gcat -1 using Ni (10 wt %)-ZrO2 that was effective at 96 kPa. Under UV/Vis light irradiation, the 13 CO2 exchange reaction and FTIR identified physisorbed/chemisorbed bicarbonate and the reduction because of charge separation in/on ZrO2 , followed by the transfer of formate and CO onto the Ni surface. EXAFS confirmed exclusive presence of Ni0 sites. Then, FTIR spectroscopy detected methyl species on Ni0 , which was reversibly heated to 394 K owing to the heat converted from light. With D2 O and H2 , the H/D ratio in the formed methane agreed with reactant H/D ratio. This study paves the way for using first row transition metals for solar fuel generation using only UV/Vis light.

Dual Photocatalytic Roles of Light: Charge Separation at the Band Gap and Heat via Localized Surface Plasmon Resonance To Convert CO2 into CO over Silver-Zirconium Oxide.

Confirmation of 13CO2 photoconversion into a 13C-product is crucial to produce solar fuel. However, the total reactant and charge flow during the reaction is complex; therefore, the role of light during this reaction needs clarification. Here, we chose Ag-ZrO2 photocatalysts because beginning from adventitious C, negligible products are formed using them. The reactants, products, and intermediates at the surface were monitored via gas chromatography-mass spectrometry and FTIR, whereas the temperature of Ag was monitored via Debye-Waller factor obtained by in situ extended X-ray absorption fine structure. With exposure to 13CO2, H2, and UV-visible light, 13CO selectively formed, while 8.6% of the 12CO mixed in the product due to the formation of 12C-bicarbonate species from air that exchanged with the 13CO2 gas-phase during a 2 h reaction. By choosing the light activation wavelength, the CO2 photoconversion contribution ratio was charge separated at the ZrO2 band gap (λ < 248 nm): 70%, localized at the Ag surface plasmon resonance (LSPR) (330 < λ < 580 nm): 28%, and characterized by a thermal energy of 295 K: 2%. LSPR at the Ag surface was converted to heat at temperatures of up to 392 K, which provided an efficient supply of activated H species to the bicarbonate species, combined with separated electrons and holes above the ZrO2, which generated CO at a rate of 0.66 µmol h-1 gcat-1 with approximately zero order kinetics. Photoconversion of 13CO2 using moisture was also possible. Water photo-oxidation step above ZrO2 was rate-limited, and the side reactions that formed H2 above the Ag were successfully suppressed instead to produce CO via the Mg2+ addition to trap CO2 at the surface.

A photofuel cell comprising titanium oxide and silver(I/0) photocatalysts for use of acidic water as a fuel.

A photofuel cell comprising two photocatalysts TiO2 and Ag-TiO2 is demonstrated. The open circuit voltage, short circuit current, and maximum electric power of the PFC were 1.59 V, 74 µA, and 14 µW, respectively. The electron flow was rectified due to the Schottky barrier between TiO2 and Ag nanoparticles.

Opening mechanism of internal nanoporosity of single-wall carbon nanohorn.

Single-wall carbon nanohorn (SWNH), which is a tubular particle with a cone cap, was oxidized in an oxygen flow at various temperatures. N(2) adsorption at 77 K, thermogravimetry (TG), differential thermal analysis (DTA), transmission electron microscopy, and Raman spectroscopy measurements were carried out on the oxidized SWNHs. The specific surface area of the oxidized SWNHs can be controlled by oxidation temperature, giving the maximum value of 1420 m(2)/g. The pore size distribution by the BJH method and the comparison plot of the N(2) adsorption isotherms of SWNH oxidized at different temperatures against that of as-grown SWNH revealed the minimum oxidation temperature for opening internal nanopores. TG-DTA analyses determined the components of as-grown SWNH: amorphous carbon 2.5 wt %, defective carbon at the cone part 15 wt %, tubular carbon 70 wt %, and graphitic carbon 12 wt %. These systematic analyses provided the exact internal nanopore volume of 0.49 mL/g for pure SWNH particles.