Density Functional Theory Study Of Adsorption Detection And Catalytic Degradation Of Cabin Formaldehyde

As an important tool for marine transportation,ships carry the majority of waterborne cargo and passenger transport operations.Due to the special characteristics and airtightness of ship cabins,water transport workers have been plagued by formaldehyde.Generally,formaldehyde contamination in ship cabins is tackled mainly by adsorption detection and catalytic degradation methods.However,the performance of formaldehyde sensing or catalytic materials in the small and high humidity environments of ship cabins is still not up to scratch.The development of materials usable for formaldehyde adsorption and degradation in the ship cabins’environment through experimental methods remains challenging.In this context,this study systematically investigates the formaldehyde adsorption or catalytic degradation properties of MXenes,CeO₂ and single or diatomic materials loaded on C₂N based on density functional theory（DFT）.On this basis,various doping sites and the corresponding adsorption after doping or removal properties for formaldehyde were investigated in detail,and potential formaldehyde sensing or catalytic materials were screened.Details of the work are as following:（1）The adsorption performance of MXenes on formaldehyde was investigated by DFT.Four cations and three halogenated anions were compared and doped at different sites on its surface.It was found that cation doping showed better performance than anion doping in enhancing the formaldehyde adsorption capacity of MXenes,which provides guidance for further design of novel formaldehyde gas detection materials.（2）Inspired by the previous study,the next detailed investigation of the formaldehyde adsorption capacity of CeO₂ with different phases,crystalline planes and adsorption sites was carried out to determine the most suitable bulk phase,crystalline planes and formaldehyde adsorption sites after expanding the doping atoms from individual anions to transition metals.The screening of 28 candidates modified CeO₂ provided five potential high performance formaldehyde adsorbents（TM-CeO₂（100）（TM=Au,Hf,Nb,Ta,Zr））.Structural and electronic property calculations showed an increase in the formaldehyde adsorption capacity due to the coupling of the d orbitals of the doped transition metals to the d orbitals of Ce atom,rearranging the outer electrons of Ce.In addition,formaldehyde sensing response testing showed that Au-doped CeO₂ exhibits high sensing sensitivity and is a potential material for formaldehyde sensing.（3）In subsequent studies,the catalysts were extended to novel single/diatomic materials.27 single-atomic and 27 diatomic materials doped by transition metals were screened based on DFT,and the results showed a strong linear relationship between the Bader charge transfer and d-band centre of the 3d metals with adsorption energies.However,the correlation between d-band centre and Bader charge with adsorption energy diminishes with increasing transition metal period.d-band centre and Bader charge are potential descriptors of the adsorption performance of formaldehyde on 3d metals doped catalysts.In terms of formaldehyde detection and catalytic properties,Hf₂-C₂N showed a strong adsorption capacity for formaldehyde due to its lower adsorption energy,and due to the strong adsorption performance of Hf₂-C₂N,H₂O and O₂ can easily generate hydroxyl radicals and superoxide radicals,which in turn are favourable for the degradation of formaldehyde.Hf₂-C₂N has a strong adsorption capacity for formaldehyde due to its lower adsorption energy for formaldehyde,and due to the strong adsorption capacity of Hf₂-C₂N,H₂O and O₂ can easily generate hydroxyl radicals and superoxide radicals,which in turn are favourable for the catalytic degradation of formaldehyde.the low potential barrier of the Hf₂-C₂N degradation pathway for formaldehyde also indicates that it is a potential dual functional material for adsorption detection and catalytic degradation.In this thesis,the ability of several substances to adsorb and degrade formaldehyde was investigated progressively by DFT.The effect of various doping atoms on the ability of the system to adsorb or degrade formaldehyde was discussed,and the mechanism of doping-induced performance enhancement was analysed by information on geometrical structure and electronic properties.Six materials,TM-CeO₂（100）（TM=Au,Hf,Nb,Ta,Zr）and Hf₂-C₂N,were designed through theoretical screening as highly efficient materials for the adsorption and degradation of formaldehyde in the marine cabin environment,providing experience and guidance for further solutions to the formaldehyde nuisance in marine transportation.