Multi-modified ZnO Photoelectrocathode Catalysis CO₂ Reduction

Increasing global energy consumption has resulted in the shortage of energy,and the excess carbon dioxide emissions,leading to a serious greenhouse effect,and threating the living environment of human beings.It is urged to find effective ways to address the lack of energy and the greenhouse effect.Our mimic natural photosynthesis is put forward to solve the problem and realize the full carbon cycle,using solar energy to convent carbon dioxide into hydrocarbons,solved the greenhouse effect problem and realized carbon energy regeneration.The main work of the thesis consists two parts.One is zinc oxide with the multiple modification of iorganic ligand and metal nanoparticles can photoelectricclly catalysic carbon dioxide reduction.The modification of zinc oxide surface enhanced photocatalytic activity and showed different selectivity to hydrocarbons.Secondly,the metal deposited on TiO₂@ZnO heterostructure can tune energy band structure that affect the activity of carbon dioxide reduction.M?Pd,Pt,Ni,Au?-TiO₂@ZnO heterojunctions show good catalytic activity of carbon dioxide reduction,due to their stabilities,excellent electronic transmission efficiency.The high electron transport efficiency of heterojunction is characterized by experiments of hole-trap.Depositing with different metals,palladium,platinum,nickel,and gold nanoparticles on the surface of heterojunction can tune the energy band structure,affecting the selectivity of carbon dioxide reduction products.Finally,we carried out the density functional calculation of the reduction potential of carbon dioxide reduction to hydrocarbon,and explored the fundamental mechanism of carbon dioxide reduction.We devise and set up a new type of photoelectrocatalytic artificial photosynthesis systems composed of ZnO or TiO₂@ZnO heterojunction photocathode,photoanode of BiVO₄,electrolyte of KHCO₃ and external Si-solar cell.The amino ligands are also used to functionalize the photocathodes of ZnO and TiO₂@ZnO via covalent linkages that can catch CO₂ molecules in situ.The nanoparticles of metals are deposited onto the surfaces of FTO glasses via electro-deposition that can absorb the protons and tune the conduction band potential.The external Si-solar cell as driving forces promotes the separation and mobility of protons and hydroxyl anions in electrolyte.Thus,photoelectrocatalytic CO₂ reduction and C-C coupling reaction take place in photocathode under irradiation of simulated sunlight.The relationships between the structures and catalytic properties of organic-inorganic composite photocathodes will be clarified by means of their electrochemical analysis and SEM,XRD,TEM,XPS spectroscopy.Our results are beneficial to explore basic scientific problems of high efficiency artificial photosynthesis.