Zhengfeng Huang

Fabrication of titanium dioxide with durable superhydrophilicity by anodization

Titanium-based materials with specific wettability show promising potential applications. In this paper, a titanium plate with hydrophilicity was simply synthesized by anodization with an electrolyte composed of NaOH, and their durability of wettability in the air was evaluated. The properties of the anodized Ti plate were characterized by a series of tests including FESEM, roughness, BET surface area, XRD, XPS, water contact angle, UV-vis absorption, photoluminescence, photocatalytic decomposition ability of methylene blue, self-cleaning property and durability of wettability in the air. When the processing time of the anodization was 10 minutes, the resulting titanium plate had a water contact angle of 0°, which proved that it was superhydrophilic, and it possessed a micro-nano composite architecture with a distinct nanofiber network chemically constituted of anatase and sodium titanate. It also exhibited excellent photocatalytic properties under UV illumination, including high photocatalytic activity and photocatalytic decomposition ability, as well as good self-cleaning properties, all of which rendered it to have good durability of wettability. Significantly, it can maintain the superhydrophilicity for 6 months in air. It is proposed that it is a synergy effect originating from the topology, chemical constitution and excellent photocatalytic properties that leads to the durable superhydrophilicity.

TiO2 surfaces self-doped with Ag nanoparticles exhibit efficient CO2 photoreduction under visible light

Doping with intrinsic defects to enhance the photocatalytic performance of TiO2 has recently attracted attention from many researchers. In this report, we developed an original approach to realise stabilized surface doping using intrinsic defects with the loading of Ag nanoparticles (AgNPs) on the surface. Herein, atmospheric pressure dielectric barrier discharge (DBD) cold plasma was used to help load the AgNPs, and ethanol treatment was used to introduce intrinsic defects (oxygen vacancies and Ti3+) on the surface of materials. This method avoids environmentally hazardous reducing regents and is undertaken under atmospheric pressure, thus reducing energy-consuming and complex operation. We combine the advantages of noble metal nanoparticles and surface doping to enhance the photocatalytic performance under the visible light. The characterization of the materials indicates that the loading of AgNPs and introduction of intrinsic defects can change the electronic structure of the composite material and improve its efficiency. The samples show significant enhancement in CO2 photoreduction to obtain CO and CH4, with yields reaching 141 μmol m−2 and 11.7 μmol m−2, respectively. The formation mechanism of the method for TiO2 modification and CO2 reduction is also discussed.

A green synthetic approach for self-doped TiO2 with exposed highly reactive facets showing efficient CO2 photoreduction under simulated solar light

Doping with oxygen vacancies and Ti3+ and engineering of the crystal morphology for exposing highly reactive facets have been demonstrated as important approaches to decrease the band gap of TiO2 and establish surface heterojunctions to enhance the photocatalytic performance of TiO2 under simulated solar light. The highly reactive facets can impact not only the CO2 reduction but also the TiO2 modification. Herein, atmospheric pressure dielectric barrier discharge (DBD) cold plasma, a green method with no environmentally hazardous reducing agents, was developed to achieve the self-doping of a TiO2 single crystal film with exposed highly reactive facets. This method combines the advantages of the special facets and crystal defects. The characterization results indicate that the DBD cold plasma method achieves the modification of the TiO2 film. The samples show remarkable improvement in reducing CO2 and H2O to CO and CH4 under simulated solar light, with yields reaching 0.075 micromol per m2 and 0.015 micromol per m2, respectively. The formation mechanisms of the method for TiO2 modification and CO2 reduction are also discussed.

Strengthening of archaeological wood using electroosmosis

Hundreds of waterlogged archaeological wooden pillars were discovered during the 2004 excavation of an archaeological site in Tianluo-Mountain, Zhejiang Province, China. These archaeological wooden pillars are invaluable cultural relics but are on the verge of decay and cracking due to the combination of a humid environment and bacterial surface erosion. Inspired by the stable silicified wood in the natural world, it was decided to silicify these fragile wooden pillars in situ to protect them. Wood was first treated in sodium silicate solution using electroosmosis technology, and then CaSiO3 precipitations were formed by immersing silicified wood in calcium nitrate solution to fix silicate in the wood. The wood microstructure before and after treatment was observed using scanning electron microscopy. It could be seen that particles were widely distributed throughout the internal part after treatment, while there were no particles present before treatment. EDS results showed that the particles are comprised mainly of silicon, calcium and oxygen, so it could be confirmed that calcium silicate was formed in the wood. Mechanical property tests indicated that the silicification process improved the axial compressive strength by 143%. Thus, archaeological wood has successfully silicified and the objective of strengthening has been achieved.