Dr. Dong Wang
Institute of materials science and engineering and institute of micro-and nanotechnologies
Technical University Ilmenau, Germany
Titanium dioxide (TiO2) has been widely used in energy storage and conversion area. However, the performance of TiO2 is substantially lower than practically required as a result of its limited solar absorption, charge transfer rate, and electrochemical activity. In this study, hydrogenated TiO2 (H-TiO2) with distinct physical and chemical properties are controllably synthesized through hydrogen (H2) plasma treatment, which exhibit excellent performance in application for lithium ion batteries, photocatalysis, electrocatalysis and photothermal conversion. Through the plasma-assisted hydrogenation, large amount of defects, such as oxygen vacancies or Ti3+ species, can be incorporated into the crystalline structures of the TiO2 nanomaterials, leading to the modification and even change of many functional properties. The microstructure of H-TiO2, and their effect on the application performance are comprehensively investigated.
Firstly, hydrogenated anatase TiO2 nanoparticles have shown a significantly improved fast lithlium storage performance. Systematic electrochemical analysis revealed that the improved rate capability of H-TiO2 results from the enhanced contribution of pseudo-capacitive lithium storage on the particle surface.
Secondly, H-TiO2 nanoparticles with different hydrogenation degrees have been investigated as photocatalyst for both dye degradation and CO2 reduction. The slightly hydrogenated TiO2 (s-H-TiO2) with the original white color exhibit enhanced photo-activity compared with the pristine TiO2; while the grey or black H-TiO2 with higher hydrogenation degrees (h-H-TiO2) display much worse catalytic performances. Further investigations reveal that the higher ratio of trapped holes (O- centers) and lower recombination rates induced by the increasing of surface defects might be the critical factors for the high activity of s-H-TiO2; on the contrary, h-H-TiO2 possess high concentrations of bulk defects, leading to the significantly decreased amount of O- centers and enhanced non-radiative recombination, which strongly inhibit their photo-activity.
Thirdly, H-TiO2 nanoparticles with large infrared absorption and dramatically enhanced non-radiative recombination, is explored as photothermal agent for cancer photothermal therapy. The results demonstrated H-TiO2 is of low toxicity, and exhibit high photothermal conversion efficiency of 40.8%, which can effectively kill cancer cells under infrared irradiation.
Finally, H-TiO2 has been investigated as electrodes of electrocatalysis for water splitting, and displayed competitive activities toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the same alkaline electrolyte, enabling the H-TiO2 as electrocatalyst for the overall water splitting.