Theoretical Design Of Two-dimensional Porous Electrocatalytic Materials Based On First Principles

During the process of electrochemical energy conversion,electrocatalysts determine the reaction rate,efficiency,and selectivity,and are the key factors affecting these energy conversion technologies.Common electrocatalytic reactions include oxygen reduction reaction(ORR),oxygen evolution reaction(OER),carbon dioxide reduction reaction(CO2RR),nitrogen reduction reaction(NRR),and hydrogen evolution reaction(HER),etc.,and these reactions usually have high overpotentials and slow dynamics.Although traditional noble metal-based electrocatalysts such as ruthenium,platinum,and iridium can accelerate the reaction rate,the high cost of these noble metals limits their large-scale applications.Two-dimensional(2D)nanomaterials are widely used in electronic devices,sensors,and catalysis due to their layered structures,unique electronic structures and physical properties.The potential of 2D materials in the field of catalysis can be summarized into three aspects:(1)larger specific surface area can provide more surface active sites;(2)excellent stability can ensure long-lasting catalytic effect;(3)good thermal conductivity can promote thermal diffusion in the reaction.Therefore,an in-depth understanding of the structure-activity relationship of 2D nanomaterials is necessary for the rational design of efficient catalysts.In this paper,we study the activity and selectivity of 2D metal-free,single-metal,and double-metal electrocatalysts in OER,CO2RR,and NRR by density functional theory(DFT)calculations,which can provide references for experimental research.The main research results are as follows:1.Research on the electrocatalytic OER and CO2RR performance of 2D metal-free π-conjugated poly(tetrathienoanthracene)(PTTA):PTTA only contains C,S,and H,phonon spectroscopy and molecular dynamics simulations confirmed the stability of PTTA.Furthermore,the 2D porous structure of PTTA can increase the number of active sites.We use DFT-based first-principle calculations to systematically explore the OER and CO2RR electrocatalytic activities of PTTA.We comprehensively investigated the intermediate structures,reaction sites,potential determining steps(PDS)and theoretical overpotentials(η)of OER and CO2RR and identified the most favorable pathway.In addition,charge density difference(CDD)and Bader charge analysis were used to analyze the electron transfer and redistribution between the adsorbed intermediates and the PTTA surface,elucidating the OER and CO2RR electrocatalytic mechanisms of PTTA,predicting its excellent electrocatalytic performance.And further demonstrate the possibility of pure organic 2D π-conjugated materials for electrocatalysis.2.Research on the electrocatalytic NRR performance of 2D single-atom catalysts(SACs):SACs have been widely used in the field of electrocatalysis,with excellent catalytic performance and high atomic utilization.In particular,SACs can also alter the adsorption selectivity of catalysts for different molecules.In this work,we explore how to engineer metal d_band centers with different coordination atoms(O,S,Se,NH)to improve electrocatalytic NRR efficiency.The whole reaction pathway of electrocatalytic NRR with MC4X4(X=O,S,Se,NH;M=Os,Ir,Ru)as catalyst was systematically studied.Electronic structural analysis showed that the NRR performance of MC4X4 depends on the regulation of the d and center of M by the coordination atoms,which in turn affects the adsorption performance of the reaction intermediates.Our findings systematically demonstrate the effect of different types of coordinating atoms on NRR activity,paving the way for the design of novel 2D SACs for NRR.3.Research on the electrocatalytic CO2RR performance of 2D diatomic catalysts(DACs):As a natural extension of SACs,DACs have received extensive attention due to their synergistic effects and regulatory differences between adjacent active sites of metal dimers.Therefore,by large-scale systematic DFT calculations,taking the 2D C9N4 substrate as an example,the selectivity of its metal dimers for CO2RR was calculated.The calculation results show that:Mn2@C9N4 has the best C1 product catalytic activity with a limiting potential of-0.49 V;and Cu2@C9N4 has the best C2 product catalytic activity with a limiting potential of-0.76 V.Density of states analysis showed that the catalytic activity of Cu2@C9N4 originated from the weak hybridization of C_p and Cu_d orbitals in*COCOH.