Synthesis Of Nitrogen-doped Carbon Materials And Their Performance For CO₂ Electroreduction

Excessive carbon dioxide emissions have a serious negative impact on the environment and climate globally.It is believed that the source of carbon dioxide emissions mainly comes from the combustion of fossil fuels.In order to minimize the rapidly rising trend of carbon dioxide emissions without hindering economic growth,the development of low-carbon renewable energy is very important.However,according to the U.S.Energy Information Administration,atmospheric carbon dioxide levels will continue to increase unless the overall energy structure changes.In order to cope with the increasing concentration of carbon dioxide in the atmosphere,efforts are being made worldwide to introduce carbon dioxide capture technology as a rich and non-toxic raw material for the synthesis of high value-added chemicals.among all methods of carbon dioxide utilization,electrochemical carbon dioxide reduction reactions utilize the electrical energy generated from renewable resources（e.g.,solar,wind,etc.）to drive the conversion of carbon dioxide.although the use of electrochemical reduction of carbon dioxide alone can not significantly reduce its atmospheric level,electrochemical reduction of carbon dioxide has attracted much attention due to its flexibility and the prospect of scalable applications.despite significant progress in recent years,the electrocatalytic CO₂reduction system provided to date has not met industrial requirements due to unsatisfactory selectivity,catalytic activity and stability.although the overall performance of the electrochemically reduced carbon dioxide system is determined by the design of catalysts,reaction media and electrochemical cells,the catalysts play the most critical role.Faraday efficiency provides an indicator of catalyst selectivity for a given product,while the partial current density of the product at a specified overpotential is a measure of catalyst activity.The ideal catalyst should be able to obtain high Faraday efficiency and high current density and long-term stability at low overpotential.At present,the emphasis of electrochemical reduction is to design and prepare electrode materials with high catalytic activity,high selectivity and good stability.Therefore,finding suitable electrode catalyst materials has become the key to solve the problem.nitrogen doped carbon-free metal materials are widely used for electrochemical reduction of carbon dioxide due to their easy availability,structural tunability and excellent catalytic performance.Although the specific surface area and nitrogen content are considered to be the two most important factors affecting the electrochemical performance of nitrogen-doped porous carbon catalysts,it does not always mean that the larger they are,the better the catalytic performance is.Herein,we developed a solvent evaporation-induced self-assembly approach to synthesize nitrogen-doped porous carbon as an efficient metal-free electrocatalyst for electrochemical reduction of carbon dioxide.In this paper,the nitrogen atom of dicyandiamide was inserted into the carbon matrix of activated carbon under the effect of high temperature induced pore shrinkage and limited to the pore.Due to the space limitation effect,the stable nitrogen atoms confined in the pores can effectively convert carbon dioxide into carbon monoxide,and the maximum faradaic efficiency of carbon monoxide in the synthesized catalysts is 48.27%.This work not only provides a promising non-metallic electrocatalyst for carbon dioxide electroreduction,but also opens up a new way to improve electrochemical performance by coordinating pore structure and active components.