The Study On Catalyst And Electrocatalytic CO₂ Reduction Coupled Anodic Reaction

Electrocatalytic CO₂ reduction is a promising alternative to fossil fuels using clean and sustainable CO₂.Currently,the electrochemical CO₂reduction technology is limited by low energy efficiency and is far from reaching the threshold of industrialization.Coupling the electrocatalytic CO₂reduction reaction with the anode reaction with low thermodynamic potential can reduce the cell voltage and improve the atomic economy of the anode and cathode reaction,which is an important way to improve the energy efficiency of CO₂reduction technology.Therefore,starting from the development of anodic catalysts based on active sites of transition metals,this paper studied the reaction properties of HMF oxidation and chlorine oxidation,and explored effective coupling strategies.The main contents and conclusions are as follows:（1）HMF is an important biomass platform chemical.We first explored the coupling effect between HMF oxidation reaction and electrocatalytic CO₂reduction reaction.HMF is a macromolecular compound containing furan ring,aldehyde group and hydroxylmethyl group.Naon catalytic materials with rich active sites on the surface are more conducive to the adsorption of HMF molecules.Based on this,starting from ZIF compounds,Ni/NC and Co/NC catalysts with abundant active sites were obtained at the anode and cathode for CO₂reduction and HMF oxidation,respectively.We found that the Faraday efficiency and yield of Zn₁Ni₂/NC catalyst CO reached 93%and the current density of CO/NC reached 190 m A cm^-2at 1.5 V（vs RHE）when the potential ranged from-0.69 V to-0.89 V（vs RHE）.Finally,Co/NC and Zn₁Ni₂/NC catalysts were used for the coupling of HMF oxidation and CO₂reduction.The anode Cl O^-Faraday efficiency is 100%,and CO Faraday efficiency is 95%in the voltage range from-0.79 to-0.99 V（vs RHE）.After electrolyzing for 16 h,the coupling performance did not deteriorate.We also found that the system cell voltage was reduced by1.2 V,confirming the coupling effect.（2）Nowaday,the chlor-alkali industry is one of the most important electrochemical reactions in the world.We also explore the coupling suitability of chlorine oxidation and electrocatalytic CO₂reduction.Different from HMF oxidation,chlorine gas will escape from the surface during chlorine oxidation reaction,and the speed of reaction is affected by diffusion.Based on this,starting from pore structure,Ni-N-C and Co₃O₄catalysts with different pore structures were synthesized for CO₂reduction and chlorine oxidation,respectively.We found that ordered mesoporous Co₃O₄has the lowest initial potential（1.7 V（vs RHE））,and the Faraday efficiency of Cl O^-remains above 80%in the range of 1.8～2.2 V（vs RHE）potential.Meanwhile,the CO Faraday efficiency of ordered mesoporous Ni-N-C reaches 99%,and the CO partial current density reaches 27 m A cm^-2.Finally,we applied the above catalysts to COR and CO₂RR coupling.The Faraday efficiencies of CO and Cl O^-reached 97%and 87%at 2.5 V,respectively,and the system cell voltage was reduced by 1.8V compared to the original.In addition,the total energy efficiency of the coupled system in a single cell electrolytic cell can exceed 70%,the weight of CO₂reduced per KWh is 318.5 g,the maximum mitigation efficiencyηis 31.9,and the lowest energy cost is 31.5$KWh^-1.