| The use of fossil fuels has made the global environmental pollution more and more serious.In order to protect our homeland on which we live,the concept of green sustainable development is increasingly welcomed by the international community today.Fuel cell technology has become one of the research hotspots in recent years because of its high efficiency and no pollution.The fuel cell device can be used as a source of electricity or environmentally friendly production of hydrogen peroxide.However,the kinetic process of Oxygen Reduction Reaction(ORR)occurring at the cathode of the fuel cell is slow,which limits the efficiency of the entire reaction process.Therefore,a suitable catalyst is required to accelerate the reaction.Currently,the main commercial catalysts used are predominantly precious metal platinum-based catalysts.However,platinum has fewer reserves in nature and is expensive.Therefore,the use of platinum-based catalysts greatly increases the cost of fuel cells and hinders the large-scale application of fuel cells.Therefore,the development of cheap and efficient non-metallic or non-precious metal catalysts is the key to large-scale application of fuel cells.In recent years,single atom catalysts(SACs)have become one of the research hotspots of non-noble metal catalysts due to their clear active sites and the ability to use 100%of metal atoms as active centers.In this paper,combined with molecular simulation calculations and thermodynamic model analysis,high-throughput calculation of the ORR catalytic performance of the bimetallic coordination electrocatalyst,the ORR catalyst that can be used as a power source and the catalyst that can efficiently catalyze the production of hydrogen peroxide are found.The main research contents are as follows:1.Study on the oxygen reduction properties of metal porphyrin structures.Through the calculation of the ORR process of the transition metal coordination porphyrin structure,it is found that the porphyrin center is the metal Cr with the best catalytic performance.Analysis of its electronic structure revealed that as the number of extraneous electrons in the metal core increases,more and more electrons occupy the anti-bonding orbit when adsorbing OH*intermediates,which weakens the bonding strength between the metal and OH*.When the center of porphyrin is metal Cr,its adsorption strength is the optimum,so its catalytic performance is the best,and its overpotential is 0.392 V.2.Study on the oxygen reduction performance of H2TPyP-M2 structures.The coordination environment at the M2 position is different from the porphyrin.In order to investigate the effect of these two coordination environments on their catalytic performance,we calculated all the cases of the 3d transition metals.The calculation found that when M2 is Sc and Ti,the ORR reaction is as follows the dissociation mechanism proceeds,and the rest of the metals follow the combined mechanism.It can be seen from the volcanic that Cu is located at the apex of the volcano,and its overpotential is 0.371 V.Comparing this structures with metalloporphyrins,it is found that the adsorption of the intermediate at the M2 position is stronger,which is due to the weak interaction between the pyridine rings connected to M2 and the oxygen atom on the side of the pyridine near the intermediate.3.Study on the oxygen reduction performance of M1TPyP-M2 structures.The M1TPYP-M2 structures contain the above two coordination environments.Using quantum chemical calculation,we explored all transition metal combinations and screened out the best catalyst CrTPyP-Cu for battery devices and ZnTPyP-Mn,ZnTPyP-Zn and ZnTPyP-Cr for hydrogen peroxide product.Through electrode potential analysis,the working voltage of CrTPyP-Cu is predicted to be～085 V.The overpotentials of catalysts ZnTPyP-Mn,ZnTPyP-Zn and ZnTPyP-Cr for producing hydrogen peroxide were 0.082 V,0.105 V and 0.107 V,respectively.Through electronic structure analysis,it is found that under certain specific metal combinations,there is a weak coupling between the two metals.After our calculation and analysis,we screened out the best four-electron ORR catalyst CrTPyP-Cu for battery systems and two-electron ORR catalysts ZnTPyP-Mn,ZnTPyP-Zn and ZnTPyP-Cr for H2O2 production,and in The electronic level understands the interaction between the two metal sites in the bimetallic catalyst,which provides help for the experimental synthesis and deep understanding of the catalytic mechanism. |
