The Study On The Solar-light Driven Catalytic Activity For CO₂ Reduction On The Ni-based Catalysts

The energy shortage caused by rapid population growth and greenhouse effect generated by enormous CO₂ emission with the development of industrialization are two major global challenges.Therefore,it is urgently desirable to exploit sustainable and clean energy which can substitute for the traditional energy,on the other hand,controlling the greenhouse effect which is the main factor for environmental pollution is deeply imperative.Solar energy act as one of the renewable energy is highly valued as it can supply energy to drive CO₂ reduction reaction,which can provide a very promising approach for both relieve the energy shortage and the emission reduction of CO₂.However,the common CO₂ reduction photocatalysts can only be simulated by UV light,which is 3%fraction of solar light.In this dissertation,different solar-light driven Ni based catalysts are reported,and characterized by XRD,HAADF,XPS and so on,the solar-light driven catalytic for CO₂ reduction on the Ni based catalysts are performed.1.It is discovered for the first time that a synergetic effect among Ni nanoparticles and CeO₂ remarkably facilitates the catalytic durability of the Ni/CeO₂ nanocomposite.We delve into the origin of the synergetic effect by combining evidences of XRD,TEM,TG-MS,FTIR,and isotope labelling:The lattice oxygen of CeO₂ in Ni/CeO₂participates in the oxidation of C*species formed on Ni nanoparticles via the migration at the Ni/CeO₂ interface,thus significantly enhancing the catalytic stability due to the inhibition of carbon deposition.It is found that the solar-light-driven thermocatalytic activity of Ni/CeO₂ is considerably improved by a novel photoactivation,which is quite different from the conventional photocatalysis on semiconductor photocatalysts.The novel photoactivation is theoretically revealed by DFT calculation:The irradiation obviously decreases the activation energy of the dominant steps of the C and CH oxidations for CRM on metallic Ni,thus considerably improving the catalytic activity of metallic Ni.2.Co-Ni/SiO₂ nanocomposite was prepared with a facile copre-capitation approach at 90?.Co-Ni/SiO₂ displays very high photothermocatalytic activity for CO₂ reduction with CH4(CRM)under the focused full-solar spectrum irradiation.Its production rates of H2 and CO(r H₂ and r CO)are 22.77 and 26.65 mmol g^-1min^-1,respectively.A very high light-to-fuel efficiency(?)of 16.79%is achieved.The high photothermocatalytic activity of Co-Ni/SiO₂ originates from effective light-driven thermocatalytic CRM and the light is discovered to provide the energy which can drive the CRM,a new photoactivation can substantially enhance the photothermocatalytic activity for CRM on Co-Ni/SiO₂.Moreover,the new photoactivation also substantially inhibits the side reaction of CO disproportionation,thus promoting the photothermocatalytic durability due to the carbon deposition being substantially reduced.3.A unique nanocomposite of Ni nanoparticles loaded on Ni doped Al₂O₃nanosheets(Ni/Ni-Al₂O₃)was prepared with a facile approach.Ni/Ni-Al₂O₃ possesses very high photothermocatalytic activity for CRM under the focused UV-Vis-IR irradiation.Its production rates of H2 and CO(r H₂ and r CO)are 27.02 and 28.71 mmol g^-1min^-1,respectively.A very high light-to-fuel efficiency(?)of 19.9%is achieved.Ni/Ni-Al₂O₃ possesses excellent photothermocatalytic durability much superior to its counterpart of Ni nanoparticles loaded on Al₂O₃ nanosheets(Ni/Al₂O₃).This is ascribed to the synergetic effect between Ni nanoparticles and Ni doped Al₂O₃ in Ni/Ni-Al₂O₃ in which oxygen in Ni doped Al₂O₃ participates in the oxidation of the formed carbon species,thus inhibiting carbon deposition on Ni nanoparticles.The high photothermocatalytic activity of Ni/Ni-Al₂O₃ originates from effective light-driven thermocatalytic CRM.A new photoactivation is discovered to substantially reduce the activation energy for CRM on Ni/Ni-Al₂O₃,thus considerably enhancing the light-driven thermocatalytic activity.Moreover,the new photoactivation also substantially inhibits the side reaction of CO disproportionation,thus promoting the photothermocatalytic durability due to the carbon deposition being substantially reduced.4.A unique nanocomposite of Ni nanoparticles loaded on Mg doped?-Al₂O₃ and?-Al₂O₃ nanosheets(Ni/Mg-?-Al₂O₃/?-Al₂O₃)was prepared with a facile grinding approach.Ni/Mg-?-Al₂O₃/?-Al₂O₃ possesses very high photothermocatalytic activity for CRM under the focused UV-Vis-IR irradiation.Its production rates of H2 and CO(r H₂ and r CO)are 32.38 and 41.99 mmol g^-1min^-1,respectively.A very high light-to-fuel efficiency(?)of 27.2%is achieved.The high photothermocatalytic activity of Ni/Mg-?-Al₂O₃/?-Al₂O₃ originates from effective light-driven thermocatalytic CRM.The Ni nanoparticlas are serve as active sites as well as the light absorber orginated from the palama absorption.A new photoactivation is discovered to substantially enhancing the light-driven thermocatalytic durability.Moreover,the new photoactivation also substantially inhibits the side reaction of CO disproportionation and accelerates the dissociation of CH4,thus promoting the photothermocatalytic durability of Ni/Mg-?-Al₂O₃/?-Al₂O₃ due to the carbon deposition being substantially reduced.