Mo/S共掺杂的石墨烯用于合成氨:密度泛函理论研究

Mo/S Co-doped Graphene for Ammonia Synthesis:a Density Functional Theory Study

工业界普遍采用Haber-Bosch方法在高温(400~600℃)和高压(150~300 atm,1 atm=0.101325 MPa)条件下催化氮气裂解和加氢而合成氨气(NH_(3)),这不仅消耗大量能源,也给环境造成很大污染。为改变这种状况,探索常温常压条件下合成NH_(3)的全新途径已成为研究热点。电催化还原N2合成NH_(3)是尚待探索的重点方向之一。本研究利用密度泛函理论计算,探讨了过渡金属元素(如Fe,Nb,Mo,W,Ru)和非金属元素(如B,P,S)共掺杂石墨烯作为该方向催化剂的可行性。结果表明,Mo和S(Mo/S)共掺杂石墨烯在NH_(3)合成中具有极低的电极电势(仅为0.47 V),其速率控制步骤涉及的中间产物为*NNH。NH_(3)合成电势比析氢反应的电势(0.51 V)低,说明N2还原制备NH_(3)具有选择性。经从头算的分子动力学计算验证,Mo/S共掺杂石墨烯体系在室温下具有良好的热力学稳定性。电子结构分析进一步揭示,过渡金属电子转移能力对高效N2电催化还原活性具有关键影响,可通过调控非金属元素对过渡金属周边配位环境的影响,优化过渡金属中心的电子结构,从而提高催化性能。

In the industrial landscape,the well-established Haber-Bosch method is employed for the catalytic synthesis of ammonia(NH_(3))from hydrogen and nitrogen gases,necessitating elevated temperatures(400--600℃)and high pressures(150--300 atm,1 atm=0.101325 MPa).In response to the imperative to reduce energy consumption and environment impact imposed by this synthetic process,significant research efforts have converged on realizing NH_(3) synthesis under ambient conditions.This study delves into the realm of N2 electrocatalytic reduction to NH_(3),using density functional theory(DFT)calculations to explore the feasibility of employing graphene co-doped with a combination of transition metal elements(e.g.,Fe,Nb,Mo,W,and Ru)and non-metal elements(e.g.,B,P,and S)as catalyst for ammonia synthesis.The findings underscore that Mo and S co-doped graphene(Mo/S graphene)demonstrates an exceptionally low electrode potential of 0.47 V for NH_(3) synthesis,with the key rate-controlling step centered around the formation of the intermediate*NNH.Especially,the ammonia synthesis potential is found to be lower than the hydrogen evolution potential(0.51 V),conclusively affirming the selectivity of nitrogen reduction to ammonia.Furthermore,through ab initio molecular dynamics calculations,the study attests to the remarkable thermodynamic stability of the Mo/S co-doped graphene system under room temperature conditions.Notably,electronic structure analysis validates that the ability of electron communication of the transition metal plays a pivotal role in dictating the efficiency of N2 electrocatalytic reduction.It can be tactically optimized through controlled modulation of the influence of the non-metal element on the coordination environment of the transition metal,thus substantially enhancing catalytic performance.