Progress in research on surface photochemical reac

The research on the surface photochemical reaction of Dalian Institute of chemical physics made progress

the research on the surface photochemical reaction of Dalian Institute of Chemical Physics they jokingly said that progress was made

January 6, 2014

[China paint information] on December 27, the scientific research team led by academician Yang Xueming of Dalian Institute of Chemical Physics, Chinese Academy of Sciences made new progress in the research on the dynamics of surface photochemical reaction, The research result "strong photon energy dependence of the photocatalytic dissociation rate of methanol on TiO2 (110)" (the effect of different photon energies on the photocatalytic dissociation rate of methanol on the surface of TiO2 (110)) was published in the latest issue of the American Chemical Society

titanium dioxide is widely used in the field of photocatalysis, but the research on its photocatalytic reaction mechanism has been exploring. A series of research results show that the electrons and holes generated by photoexcitation of titanium dioxide will soon relax to the bottom of the conduction band or the top of the valence band, and the excess energy will be converted into phonon energy, which basically does not contribute to the reaction. The widely accepted photocatalysis model believes that the photocatalysis reaction rate mainly depends on the number of effective electron hole pairs generated by light, that is, the chemical reaction process is related to luminous flux, but has no obvious relationship with the excitation light wavelength (or the energy of electrons and holes generated by light excitation)

Yang Xueming led the team to systematically study the reaction kinetics of TiO2 (110) surface covered by methanol monolayer after UV irradiation by using the self-developed surface photochemistry device based on high sensitivity mass spectrometry. Early results (J. am. chem. soc., 2012, 134 (32), 13366 – 13373, J. am Chem. Soc., 2013, 135 (28), 10206 – 10209) showed that methanol formed formaldehyde through the breaking of O-H and C-H bonds during illumination, and a large number of dissociated hydrogen atoms were transferred to the nearby bridge oxygen atoms. In the process of surface heating, some hydrogen atoms will seize the bridge on the surface, and the oxygen atoms will first desorb from the surface in the form of water (H2O), resulting in surface oxygen vacancies. With the increase of surface oxygen vacancy concentration, the remaining hydrogen atoms on the bridge oxygen are easier to combine into hydrogen molecules and escape

in this study, the quantum yield of photodissociation of methanol molecules at 266 nm is about two orders of magnitude higher than that at 355 nm, while the absorption efficiency of TiO2 at 266 nm is only twice that of 355 nm. The experimental results show that the photon energy (the energy of electrons and holes) has an important impact on the photocatalytic efficiency. A possible mechanism explanation is that electrons and holes generated by light excitation directly interact with methanol molecules to induce chemical reactions, rather than relaxation and then interact with methanol molecules to induce reactions. Another possible explanation is that the electrons and holes generated by photoinduced excitation combine to generate high excitation mode phonons, which excite some vibration modes of molecules after coupling with methanol molecules. Industrial dust pollution promotes the dissociation of methanol due to its large amount and relatively concentrated pollution sources

if true, test width: 450mm, effective stretching stroke 800mm; The fixture of the universal material testing machine moves at a uniform speed at the rate of 100 ± 20mm/min; The minimum length of the clamping surface of the universal material testing machine is 45mm in the direction of the force. As a transparent material with excellent comprehensive properties, the essential mechanism of photocatalytic reaction on the surface of titanium oxide, which is mechanically or pneumatically fixed, will provide better support for the design and development of efficient catalysts and the improvement of photocatalytic models

the above research was supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences