As an important raw material, TiO2 has been widely used in industries closely related to human life, such as coatings, sunscreens, and food additives. The global market size in 2019 reached 16.64 billion US dollars, and the compound growth rate in the next five years is expected to be as high as 7.6%. However, these TiO2 materials mainly exist in the form of powder on the macroscopic level, which can easily enter the human body through the respiratory system, thereby causing health risks. Therefore, on February 18, 2020, the European Union officially listed "mixtures in powder form containing 1% or more of titanium dioxide which is in the form of or incorporated in particles with aerodynamic diameter ≤10 μm" as a category two carcinogen. In addition, these nanomaterials are difficult to recycle, and once released into the environment, they will be biologically toxic to animals and plants in nature. Therefore, it is a challenging task to develop and use self-supporting TiO2 materials with high safety factor and easy recycling.
Recently, Academician Yu Jianyong, Professor Ding Bin, and Professor Liu Yitao of the Textile Technology Innovation Center of Donghua University reported on a new form of TiO2—ultra-light and highly elastic TiO2 nanofiber aerogel. They used flexible TiO2 nanofibers as the building block, a small amount of SiO2 sol as a chemical crosslinking agent, and used the method of freeze molding to realize the directional assembly of TiO2 nanofibers, and prepared TiO2 nanofibers with ordered cell structure. glue. The nanofiber aerogel can be repeatedly compressed at a strain of up to 40% without obvious plastic deformation, and exhibits excellent dynamic mechanical properties. In addition, the nanofiber aerogel also has ultra-low bulk density (0.5 mg cm-3) and ultra-high porosity (>99%). Further, abundant oxygen vacancies are generated by the reduction of lithium metal, thereby effectively regulating the electronic structure of TiO2, and its electrical conductivity is as high as 38.2 mS cm-1.
As a proof of concept, the researchers used the nanofiber aerogel as a new type of self-supporting electrocatalyst for environmental nitrogen fixation, showing excellent electrocatalytic activity. In addition, the nanofiber aerogel exhibits excellent durability in acidic, alkaline and neutral electrolytes. Density functional theory (DFT) calculations show that the presence of oxygen vacancies can promote the adsorption and activation of nitrogen, thereby helping to improve electrocatalytic activity. In addition to applications in the field of electrocatalysis, highly conductive, ultra-light, and highly elastic TiO2 nanofiber aerogels also have broad application prospects in the fields of energy storage, photocatalysis, and flexible electronic devices.
Related work was published on Angewandte Chemie International Edition, DOI: 10.1002/anie.202010110 under the title "Conductive and Elastic TiO2 Nanofibrous Aerogels: A New Concept toward Self-Supported Electrocatalysts with Superior Activity and Durability".