Preparation Of Cu Nanoparticle Modified Two-dimensional Layer Materials And Their Application In CO₂ Reduction

With the development of society, the continuous consumption of fossil energy and environmental pollution are two major challenges for human beings. Since the discovery of the photocatalytic properties of titanium dioxide by Fujishima in 1972, optical （electric）catalysis has become the study focus around the world to solve the energy and environmental problems. Although photocatalysts and electrocatalysts have been extensively studied, they still face many issues. For example, classical TiO2 catalyst cannot effectively utilize visible light, and the electrocatalyst often has a high overpotential. Therefore, in order to improve the performance,it is necessary for us to explore new types of catalysts and modify classical catalysts to overcome their shortages.It is well known that the performance of catalysts can be improved by fully taking advantage of electrons and making more electrons involved in the catalytic reduction of CO2. For electrocatalysts, the deposition of metal nanoparticles can not only increase the conductivity of the material, but also increase the reactive sites of the electrocatalysts,which leads to the improved utilization of the electrons and thus the increase of the Faraday efficiency. Similar to photocatalysts, reducing the size of the material and constructing the hierarchical structure can make the transfer path of the photogenerated electrons shorter and the separation of electrons and holes more efficient. Therefore, the purpose of increasing the quantum efficiency and improving the performance of the photocatalyst and can be achieved. In addition, because of the high specific surface area and many active sites, new two-dimensional layered materials have become the hot research area. Additionally, the ultrasmall metal nanoparticles also have significant plasma resonance effect and excellent electrocatalytic performance. Based on the above mentioned, in this thesis, Cu nanoparticle modified two dimensional layered materials have been prepared and their property and performance for CO2 reduction were studied as well. The details are as follow.1) Cu/MoS₂ composite catalysts were synthesized by a simple hydrothermal method for electrocatalytic reduction of CO2. First, the MoS₂ nanosheets were prepared by one-step hydrothermal method, and then the Cu nanoparticles were deposited on the two-dimensional MoS₂ nanosheets by microwave hydrothermal method. The designed optimal hierarchical Cu/MoS₂ composite not only exhibited remarkably enhanced electronic conductivity and specific surface area but also possessed improved CO2 adsorption capacity, resulting in a significant increase in overall faradaic efficiency and a 7-fold augmentation of the faradaic efficiency of CH4 in comparison with bare M0S₂. In addition, the Cu/MoS₂ composite had superior stability with high efficiency retained for 48 h in the electrochemical process. It is anticipated that the designed Cu/MoS₂ composite electrocatalyst may provide new insights for transition metal sulfides and non-noble particles applied to CO2 reduction.2) Two dimensional layered C₃N₄ with large specific surface area was prepared by high temperature calcination method, and then Cu nanoparticles were deposited on the surface of the C₃N₄ nanosheets by microwave hydrothermal method. The designed Cu/C₃N₄ composite had enhanced absorption ability of visible light, and the loaded Cu particles was beneficial for the separation of photogenerated carriers. In addition, the small Cu particles also functioned as good reaction sites. The CO yield over Cu/C₃N₄ composite catalyst was significantly higher than that over pure C₃N₄ nanosheets.