Synthesis Of Carbon Composites And Electrochemical Performance For Carbon Dioxide Reduction

As one of the emerging technologies for carbon dioxide resource conversion,electrochemical reduction of carbon dioxide can be drived by renewable energy to reduce carbon dioxide into high value-added fuels and fine chemicals.However,it is also facing serious problems,such as much slow reaction rate and strong side reaction of hydrogen evolution.Therefore,developing efficient,stable and inexpensive catalysts is still a key challenge for electrochemical reduction of carbon dioxide technology to promote the reaction rate at current.In this research paper,with using different design ideas,construction strategies,and synthetic techniques,two kinds of carbon composites were prepared,based carbon materials as conductive substrates.The performance of two kinds of carbon composites was explored for electrochemical reduction of carbon dioxide.The main research contents and results are as follows:Ni-N-C composites were prepared by ball milling and carbonation process using cheap biomass tannins as carbon source,melamine as nitrogen source and nickel acetate as metal source respectively.The effects of different temperatures and compositions on performance for carbon dioxide reduction were studied.The effects for the specific ratio of different nitrogen species on the activity were explored,and the source of catalytic activity was also speculated based on the experiment results.The research results manifest that the Ni-N-C composites exhibit the most excellent performance for carbon dioxide reduction at a carbonization temperature of 800°C.In 0.1 M KHCO₃,carbon monoxide Faraday efficiency is as high as94.8%at-0.86 V vs.RHE,and the carbon monoxide partial current density reaches 18.2 mA cm^-2.It can be stablely operated for 25 h.Cu₂O@Cu-MOF was prepared by in-situ chemical etching using cuprous oxide as copper source and 1,3,5-benzenetricarboxylic acid as ligand.The Cu₂O@Cu-MOF/C was prepared by ultrasonic mixing with conductive carbon.It is used as an electrode material for electrochemical reduction of carbon dioxide.On that basis,the changes of materials structure,morphology and composition were investigated with different etching time,and the performance of as-prepared composites for electrochemical reduction of carbon dioxide were also studied with different compositions.It was found that Cu₂O@Cu-MOF/C exhibited the most excellent electrochemical performance for carbon dioxide reduction compared to Cu₂O/C and Cu-MOF/C.In 0.1 M KHCO₃ electrolyte,at-1.71 V vs.RHE,the Faraday efficiency of hydrocarbons can reach 79.4%.The Faraday efficiency of methane can be up to 63.2%,and the partial current density reaches 8.4 mA cm^-2 exhibiting a prominent methane selectivity.