Synthesis And Studies Of Two Dimensional Transition Metal-based Materials For Electrocatalytic Reduction Application

Air pollution and greenhouse effect,caused by the burning of carbon-based fossil energy,are becoming more and more serious.It is necessary to develop sustainable clean energy sources such as solar energy,wind energy and water conservancy energy to curb this trend.At the same time,it is vital to develop complementary electricity-based applications for this purpose.Electrochemical catalytic reduction is such a powerful way,which can realize catalytic conversion of chemicals by using sustainable electric energy.But the electrolysis process consumes a lot of energy due to the high overpotential of the reaction.Thus,developing catalyst with high performance and low over potential is the theoretical key to solve this problem.In this paper,transition metal based two-dimensional materials was studied for the application of electrochemical hydrogen production(HER),electrochemical carbon dioxide reduction(ECR)catalyst.An iron doped high(110)crystal face catalyst FeNiSe-EG was constructed.In the alkaline environment,the obtained electrode exhibits excellent HER activity with small overpotentials of-187 and-222 mV at current densities of 10 and 20 mA cm-2,and have a low Tafel slope of 65 mV dec-1.Theoretical calculation shows that iron doping and high(110)crystal face synergism promote the activity of electrochemical hydrogen production.This character makes the catalyst suitable for more mild alkaline HER in industrial applications.Ni-based materials often show up excellent electrochemical hydrogenicity.Then,graphene based material with carbon-coated nickel nanoparticles was designed and synthesized.Through characterization,it is found that it has excellent electrocatalytic carbon dioxide reduction activity,the Faraday efficiency of CO can reach 98.82%,and the current density is-17.36 mA cm-2 at-0.7 V,excel nickel and nitrogen doped catalystsTo solve the problem of low efficiency of CO Faraday in the ECR process,a graphene-based Cu and N co-doped two-dimensional structure monatomic catalyst Cu-N2/GN was designed and prepared.Benefitting from the unsaturated coordination environment and atomic dispersion,the Cu-N2/GN nanosheets exhibit a high electrocatalytic ECR activity and selectivity for CO production with an onset potential of-0.33 V and the maximum Faradaic efficiency of 81%at a low potential of-0.50 V,superior to those of previously reported Cu-based/carbon materials for ECR to produce CO.Theoretical calculations further demonstrate that the weak adsorption energy between Cu-N2 sites and CO2 reduces the potential barrier of CO2 activation;meanwhile,the short bond lengths of Cu-N2 sites can enhance the electron transfer,thus boosting the CO generation.In this paper,the problem of low conversion rate and high over potential during the electrochemical reduction of these energy molecule was solved by designing two-dimensional transition-metal based materials,which provides an idea for the application of this technology.