Studies On The Construction Of Silicon-based Nanowire Photoelectrode For The Photoelectrocatalytic Reduction Of CO₂ And Production Of Adipic Acid From Cellulose Via The 2,5-furandicarboxylic Acid

Efficient use of carbon dioxide and catalytic conversion of renewable biomass resources are important for addressing the environmental and energy issues.This dissertation mainly focuses on the p-Si nanowire arrays(SiNWs)photoelectrode for the photoelectrocatalytic reduction of CO2 and Pt nanoparticles(Pt NPs)loaded on the niobic acid(Nb2O5·xH2O)for the hydrodeoxygenation of 2,5-Furandicarboxylic acid(FDCA)to adipic acid(AA),and obtains the following main results:Aiming at the research on the performance for the photoelectrocatalytic reduction of CO2,p-Si is a photocathode material with great potential application value due to its unique advantages.This dissertation acquired the SiNWs via the metal-assisting chemical etching method.The morphology of SiNWs was optimized by adjusting the silver precipitation time,H2O2 concentration,etching time and HF concentration.When the silver precipitation time,H2O2 concentration,etching time and HF concentration were 1 min,0.5 M,45 min and 4.6 M,respectively,the order morphology of SiNWs could be obtained.SiNWs was prone to take place the hydrogen evolution reaction(HER)for the CO2 reduction,and the activity and selectivity of CO2 reduction were poor.The addition of Ag cocatalyst could significantly increase the activity and selectivity of CO2 reduction.Therefore,by adjusting the size of Ag NPs(4.2-16 nm),it was possible to obtain the syngas with different H2/CO ratios(1-4).At the same time,the possible reaction mechanism for CO2 reduction to CO formation and the effect of different size of Ag NPs on the CO2 reduction to CO were also proposed.Aiming at the research for the hydrodeoxygenation of FDCA to AA,the excellent performance Nb2O5-xH2O-supported Pt(Pt/Nb2O5·-xH2O)catalyst was developed.Compared with other supports such as SiO2,Al2O3,TiO2,MgO and HZSM-5 supported Pt catalysts,Pt/Nb22O5·xH2O showed higher selectivity and yield of AA,which might be related to the strong Br(?)nsted acid of Nb2O5·xH2O and beneficial for activating and breaking the C-0 bond of NbOx species.The catalytic performances of other noble metals(Pd?Ru?Rh?Ir)loaded on the Nb2O5·xH2O support were also compared.It was found that Pt still maintained the best catalytic performance.Pd was mainly applied to the hydrogenation of the furan ring,whereas other noble metals were mainly used for the cleavage of C-C bonds or the over-hydrogenation of carboxyl groups.Under the suitable reaction conditions(433 K,8 h),the effect of Pt NPs state and size on the catalytic performances of Pt/Nb2O5·xH2O were studied.The results showed that the highest yield of AA was obtained on the 3.8 nm,which was the highest value of FDCA to AA by the one-step method.Further research indicated that FDCA had experienced the intermediate species such as THFDCA and HAA,and possible reaction path for the hydrodeoxygenation of FDCA to AA was proposed.