CO₂ Electroreduction System Design And Novel Electrocatalytic Reaction Investigation

To achieve the goal of peaking carbon dioxide emissions by 2030 and being carbon neutral by 2060,the current fossil energy-based industrial system is in urgent need of revolutionary technological change.Renewable electricity-driven chemical synthesis uses clean renewable electricity as an energy source,with mild reaction conditions,which can replace traditional fossil fuel-driven chemical synthesis under high temper-ature and high pressure.Electrifying chemical manufacturing is of great significance to the decarbonization of the chemical industry.Additionally,renewable energy power generation exhibits strong seasonal fluctuations.Existing energy storage technologies are limited by high costs and energy losses and cannot meet the requirements of sea-sonal storage.Electrifying chemical manufacturing can be coupled with renewable en-ergy generation,which is an ideal way to store seasonal energy and utilize surplus elec-tricity.Electrifying chemical manufacturing has broad prospects in replacing traditional chemical production with intensive carbon dioxide emissions and solving seasonal en-ergy storage of intermittent renewable energy.However,the current research on the electrifying chemical manufacturing is still in the early stages.In order to design a highly selective and energy-efficient catalytic system for the electrifying chemical man-ufacturing,it calls for efforts in better catalyst design,electrolyzer intensification and exploration of new electrocatalytic reactions.This work starts with the electrocatalytic reaction of carbon dioxide and proposes a molecular-functionalized Pd/C catalyst for highly selective synthesis of CO.With the help of gas diffusion electrodes and microfluidic electrolyzers,high-selectivity genera-tion of carbon monoxide was achieved at industrially relevant current densities.At a potential of-0.65 V vs RHE,a carbon monoxide Faradaic efficiency of 93%was achieved,which corresponds to a current density of 300 m A cm^-2.Combining the car-bon monoxide temperature programmed desorption experiment and in-situ surface en-hanced total reflection Fourier transform spectroscopy,the influence of the molecular functionalization of the quaternary ammonium salt polyelectrolyte on the electron transfer of Pd and the intensity of CO adsorption was studied,and the mechanism of increasing the selectivity of carbon monoxide was revealed.In order to improve the selectivity of multi-carbon products（C2+）such as ethylene,ethanol,acetic acid,and increase the feedstock conversion,this work systemati-cally compares the electrocatalytic reduction of carbon dioxide to C2+products and car-bon monoxide to C2+products.Under different CO2/CO feedstock flow rate and partial pressure conditions,the C2+product selectivity and the carbon efficiency of the feed-stocks（the mass of carbon in the product/the total amount of carbon in the feedstocks consumed）were studied,and then the cascade reaction of carbon dioxide electrocatal-ysis was proposed.That is,the two-step method of electrocatalytic reduction of carbon dioxide to carbon monoxide and electrocatalytic reduction of carbon monoxide to multi-carbon products is a feasible way to improve the selectivity of multi-carbon prod-ucts in carbon dioxide electroreduction,solve the loss of carbon dioxide raw materials and increase carbon utilization.By synthesizing an oxide-derived copper plate catalyst,at a potential of-0.59 V vs RHE and a current density of 200 m A cm^-2,a selectivity of84%for the electroreduction of carbon monoxide to multi-carbon products was achieved.Currently,electrifying chemical manufacturing is still limited at small scale due to low selectivity and faraday efficiency.For this reason,exploration of new electrocatal-ysis synthesis reaction system has drawn significant attention.This work for the first time achieves high selectivity of electrocatalytic reduction of acetonitrile to ethylamine.Unlike conventional high temperature/pressure acetonitrile hydrogenation processes,the acetonitrile electrocatalytic reduction under room temperature/pressure utilize water as protons source donors.Ethylamine Faradaic efficiency at-0.29 V vs RHE achieves95%with minimal formation of secondary and tertiary amine by-products.Impacts of different metal catalysts,acetonitrile concentration,and p H value on the reaction were further studied.At high current density of 1 A cm^-2,the electrocatalytic reduction of acetonitrile still maintains high ethylamine selectivity.The electrochemical differential mass spectrometry analysis of the in-situ flow electrolytic cell revealed the reaction mechanism of secondary and tertiary amines formation,and the density functional the-ory calculations further clarified the reaction mechanism of the electrocatalytic reduc-tion of acetonitrile on different metal catalysts.