含CoN_(x)中心的石墨烯电催化氧还原反应机理研究  

Study on the Mechanism of Oxygen Reduction Reaction on Graphene with CoN_(x) Centers

作　　者：张静[1] 崔丹丹 杨钧钰 刘一鸣 ZHANG Jing;CUI Dan-dan;YANG Jun-yu;LIU Yi-ming(School of Chemical Engineering and Technology,Taiyuan University of Science and Technology,Taiyuan 030024,China)

机构地区：[1]太原科技大学化学工程与技术学院,山西太原030024

出　　处：《分子催化（中英文）》2024年第6期550-559,I0003,I0004,共12页Journal of Molecular Catalysis(China)

基　　金：国家自然科学基金(22075197,22278290);山西省科技合作交流专项项目(202204041101029);山西省基础研究计划(自由探索类)项目(20210302123214)。

摘　　要：采用理论计算方法深入研究了两种含三配位CoN_(x)(x=2,3)中心的石墨烯(CoN_(x)-G)催化剂在氧还原反应(ORR)中的催化机理.在这两种催化剂表面,ORR的最低能量反应路径遵循相同的机制:O_(2(ads))分子首先加氢还原为OOH_((ads)),随后OOH_((ads))加氢解离为两个OH_((ads)),最终OH_((ads))继续加氢还原为产物水.在CoN_(2)-G上,整条反应路径中OH_((ads))还原为H2O(ads)具有最高能垒;而在CoN_(3)-G表面,O_(2(ads))还原为OOH_((ads))具有最高能垒.相比CoN_(2)-G,CoN_(3)-G具有较低的最高势垒,更佳的结构对称性,更负的形成能,且在ORR过程中Co中心始终保持正电荷,有利于含氧中间体的活化.因此,CoN_(3)-G表现出比CoN_(2)-G更优良的ORR催化性能,归因于配位的三个N原子对Co位点电子结构的优化以及体系稳定性的增强.The oxygen reduction reaction(ORR)catalytic mechanism of two graphene(CoN_(x)-G)catalysts containing CoN_(x)(x=2,3)centers was investigated using theoretical computational methods.On both catalysts,the lowest-energy reaction pathway for ORR follows the same mechanism:the O_(2(ads))molecules are first hydrogenated and reduced to OOH_((ads)),which then undergoes hydrogenation and dissociation to produce two OH_((ads))molecules,and finally the OH_((ads))continues to hydrogenate and reduce to form water.The key difference lies in the fact that the reduction of OH_((ads))to H2O(ads)on the CoN_(2)-G structure serves as the highest energy barrier(HEB)step of the entire pathway,whereas on the CoN_(3)-G structure,the reduction of O_(2(ads))to OOH_((ads))is the HEB.Compared to CoN_(2)-G,CoN_(3)-G exhibits a lower HEB,a better structural symmetry,more negative formation energy,and maintains a positive charge on the Co centers throughout the ORR process,which facilitates the activation of oxygen-containing intermediate.Consequently,CoN_(3)-G shows a better ORR catalytic performance than CoN_(2)-G,which is attributed to the optimization of the electronic structure of the Co sites and the enhancement of system stability through the coordination of three N atoms.

关 键 词：CoN_(x)-G催化剂 催化机理 反应势垒 氧还原反应 密度泛函理论 

分 类 号：O643.32[理学—物理化学]