Structural Design And Thermodynamics Performance Study Of Cathode Catalysts For Fuel Cell Equipment

Hydrogen fuel cell as a key technology for efficient conversion and utilization of hydrogen energy drives the future energy revolution.The slow thermodynamics of hydrogen fuel cell constrains the fuel cell output power.Although single-layer carbon-supported non-precious metal structure catalysts show the potential to replace precious metals,the stability and thermal efficiency still face great challenges.To address the problem of low efficiency of fuel cell oxygen reduction reaction,this paper designs a non-metal doped single-layer carbon-supported non-precious metal catalysts structure using density flooding theory,obtains the law of non-metal influence on the activity of transition metal-nitrogen-carbon structure,probes the mechanism of different non-metal influence on the dynamic microenvironment of active sites,and obtains a high performance cathode catalyst structure.The details are as follows.（1）Structural design,geometry optimization and thermal stability verification of non-metallic modulated FeN_3/4A and FeCoN_5/6A structures.The non-metallic doped Fe-N-C and Fe Co-N-C structures were designed and optimized using a density flooding theory approach.The formation energy results show that the left zone non-metal A-doped structures are more stable compared to the right non-metal doped structures;The molecular dynamics simulation results show that the structure can operate stably at the operating temperature of the fuel cell,and the cathode catalyst structure doped with N and C atoms is more thermodynamically stable.（2）The effect of different non-metallic A doping on the working properties of single and double transition metal structures was investigated.A"computational hydrogen electrode model"was used to calculate the Gibbs free energy of the structures and to evaluate the thermodynamic properties.The results show that the monometallic FeN_3/4A structure is too strong for the adsorption of oxygen-containing intermediates and the working rate limiting step protonates^*OH to water,while the bimetallic FeCoN_5/6A structure can improve the adsorption of oxygen-containing intermediates;the P and S atom doping can improve the weak adsorption problem,and the B,C,N and O atom doping can improve the strong adsorption problem.The best active FeCoN₅C_1-1 structure was obtained（working potential up to 0.917 V,which is larger than 0.78 V of Pt）,and the improved thermal efficiency of the fuel cell cathode.（3）The effect of electronic structure of FeN_3/4A and FeCoN_5/6A active sites on the adsorption performance was investigated.The electronic orbital arrangement and electron transfer of the active center and its microenvironmental atoms were calculated using the fractional wave density of states and the Bard charge.The results show that the active site of FeN_3/4A has a larger d-orbit center than FeCoN_5/6A and has stronger adsorption of oxygen-containing intermediates;the determinant of the outermost p-electron number and electronegativity construction of nonmetal A gradually increases with the increase of A atomic number,which is favorable to the exothermic process of oxygen adsorption,but too strong adsorption also leads to difficult desorption of products.the structure of FeCoN₅C_1-1 has a suitable adsorption and desorption potential,and a high fuel cell cathode conversion efficiency is obtained.