A series of proto-type photocatalytic air purifier(AP(Nx-Cy))systems are built with a nitro-gen-doped TiO2(N-TiO2)-impregnated honeycomb(HC)filter for photocatalytic decomposition of 0.5-5 ppm formaldehyde(FA:CH2O)vapor under varying conditions and UV-LED light(1 watt).The binary codes of Nx and Cy in AP systems are used as the composition identifiers to represent N/Ti molar ratios(0 to 20)and N-TiO2 concentration(2 to 20 mg mL-1),respectively.The AP(N10-C10)is found as an optimum unit with the highest capability to boost the catalytic conversion of CH2O to CO2(yield=89.2％over 10th cycles and the clean air delivery rate(CADR)of 9.45 L min-1 in dry air).The superior charge carrier lifetime(τa:1.70 ns)of N10-C10 over others(e.g.,1.37 ns for pure TiO2)should indicate the influential role of N-defects(No)in reducing the bandgap(3.10 eV)and in creat-ing defect-related oxygen vacancy(OVs-Ti3+)states as predicted by the density functional theory(DFT)simulation.The photocatalytic oxidation pathway of CH2O,when assessed by diverse ap-proaches(e.g.,in-situ diffuse reflectance infrared Fourier transform,electron paramagnetic reso-nance,and DFT analyses),is found to involve several energetically favorable intermediate steps(such as exothermic covalent adsorption of CH2O to bridged O/OH groups on TiO2-OV {110} surface in the form of CH2O2 followed by catalytic dehydrogenation/oxidation reactions to yield CO2 through direct route:CH2O2/HCOO-+·OH → H2O+CO2).These steps are supported by the calcu-lated density of states(DOS)for chemically active Ti-atom on {101} surface with N-impurity.The presence of No-defects and OVs is expected to influence the reaction energetics and intermediates for efficient mineralization in humidified conditions by lowering the activation barriers.This study offers valuable insights into the design and construction of an advanced photocatalytic system for efficient mineralization of aldehyde VOCs in ambient air.
关键词
光催化蜂窝过滤器/甲醛/氮掺杂TiO2/密度泛函理论计算/催化反应途径/空气净化
Key words
Photocatalytic honeycomb filter/Formaldehyde/Nitrogen-doped TiO2/Density functional theory calculations/Catalysis reaction pathways/Air purification
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基金项目
National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(MSIT)of the Korean government(2021R1A3B1068304)
NRF funded by MSIT of the Korean government(RS-2023-00243840)
Brain Pool program(RS-2023-00222393)
Jiangsu Innovative and Entrepreneurial Talents Project()
Ministry of Science and Education of Russian Federation(FEUZ-2023-0013)
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