Abstract
Single-atom catalysts(SACs)have been widely utilized in electrochemical nitrogen reduction reactions(NRR)due to their high atomic utilization and selectivity.Owing to the unique sp/sp2 co-hybridization,graphyne materials can offer stable adsorption sites for single metal atoms.To investigate the influence of the sp/sp2 hybrid carbon ratio on the electrocatalytic NRR performance of graphyne,a high-throughput screening of 81 catalysts,with 27 transition metals loaded on graphyne(GY1),graphdiyne(GY2),and graphtriyne(GY3),was conducted using first-principles calculations.The results of the screening revealed that Ti@GY3 exhibits the lowest energy barrier for the rate-determining step(0.32 eV)in NRR.Further,to explore the impact of different sp/sp2-hybridized carbon ratios on the catalytic activity of SACs,the mechanism of nitrogen(N2)adsorption,activation,and the comprehen-sive pathway of NRR on Ti@GY1,Ti@GY2,and Ti@GY3 was systematically investigated.It was found that the ratio of sp/sp2-hybridized carbon can significantly modulate the d-band center of the metal,thus affecting the energy barrier of the rate-determining step in NRR,decreasing from Ti@GY1(0.59 eV)to Ti@GY2(0.49 eV),and further to Ti@GY3(0.32 eV).Additionally,the Hall conductance was found to increase with the bias voltage in the range of 0.4-1 V,as calculated by Nanodcal software,demonstrating an improvement in the conduc-tivity of the SAC.In summary,this work provides theo-retical guidance for modulating the electrocatalytic nitrogen reduction activity of SACs by varying the ratio of sp/sp2 hybrid carbon,with Ti@GY3 showing potential as an excellent NRR catalyst.
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