Ultrathin Metal Nanosheet/Graphene Composite Catalyzes The Electroreduction Of Carbon Dioxide

The burning of traditional fossil fuels such as coal,oil,and natural gas in the air emits large amounts of CO₂ gas,disrupting the natural carbon cycle and causing a series of environmental problems such as global warming and sea level rise.Electrocatalytic CO₂ reduction is the conversion of CO₂ into economically valuable chemical products by using electricity generated from renewable energy sources,which can realize high value-added utilization of CO₂.The lack of efficient catalysts has been one of the bottlenecks preventing the industrialization of CO₂ reduction.Metallic materials are widely used in CO₂electrocatalytic process because of their high activity and conductivity,but they also suffer from problems such as small specific surface area,low active site utilization,easy agglomeration,and poor electrical conductivity.For this reason,this thesis focuses on stabilizing the structure of metal catalysts and promoting their active site exposure by compounding two-dimensional metal nanosheet materials with graphene materials to enhance their electrocatalytic CO₂ reduction performance as follows.（1）The nitrogen-doped graphene nanosheets（NG）were loaded with high curvature willow-like Cu O nanosheets in situ by a reduction-then-oxidation synthesis strategy,and the surface of the willow-like Cu O nanosheets was reconstructed by simple calcination under nitrogen atmosphere to form willow-like Cu O nanosheets rich in disordered grain boundaries of Cu O（110）/Cu O（111）and with high curvature structure.nanosheets with high curvature structure.In this paper,the high curvature Cu O nanosheet structure and disordered grain boundaries were combined to prepare Cu O/NG composites for CO₂RR,and the Faraday efficiency of C₂H₄ could reach 29%at-1.3 V vs RHE,and the selectivity of C₂H₄ in the carbon-containing product reached78%with an ethylene/methane ratio of 190.（2）In₂S₃-RGO composites with predominantly exposed In₂S₃（440）crystal planes were prepared by interfacially induced dominant crystal plane growth using graphene oxide nanosheets（GO）as the substrate,and it was demonstrated by DFT theoretical calculations that（440）has the lowest surface energy among the three crystal planes（311）,（440）and（400）during In₂S₃ crystal growth and can The surface energy of（440）is the lowest among（311）,（440）and（400）crystalline planes during the growth of In₂S₃crystals.The DFT theoretical calculations also demonstrate that the（440）crystalline surface of In₂S₃ has a good selectivity for HCOOH production during CO₂RR.Using the composite of In₂S₃-RGO for CO₂RR,the Faraday efficiency of HCOOH can reach91%at-1.2 V vs RHE.（3）Se-doped Bi₂O₃/RGO composites were synthesized by hydrothermal method using graphene oxide nanosheets（GO）as the substrate,and it was found that the catalytic performance of Bi₂O₃ could be effectively enhanced by Se doping,and the Faraday efficiency of formic acid was increased from 69%to 93%.