Rational Design of Electrocatalysts Comprising Single-Atom-Modified Covalent Organic Frameworks for the N2 Reduction Reaction: A First-Principles Study
Rational Design of Electrocatalysts Comprising Single-Atom-Modified Covalent Organic Frameworks for the N2 Reduction Reaction: A First-Principles Study
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DOI：
10.1021/acs.jpcc.1c02832
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发表时间：
2021-05
影响因子：
3.7
通讯作者：
K. Ohashi;Kazuyuki Iwase;T. Harada;Shuji Nakanishi;K. Kamiya
中科院分区：
文献类型：
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作者：
K. Ohashi;Kazuyuki Iwase;T. Harada;Shuji Nakanishi;K. Kamiya
电催化N2还原反应（NRR）是一种最有前途的就地和按需生产NH3的方法之一。单金属原子掺杂的共价有机框架（COF）预计将作为有效的NRR电催化剂，因为设计的金属中心的配位环境是可作为COF的广泛的可能设计的结果。在此，我们使用密度泛函理论（DFT）系统地研究了各种单一的3d-金属原子掺杂到COFs与不同的配位数的理论NRR活性，以获得一个通用的设计准则，高效的NRR催化剂的开发。NRR中间体的吸附强度随着金属中心的配位数或d-电子数的增加而降低。电位决定步骤根据NRR中间体的吸附强度在N-N键活化和NH3脱附之间切换。因此，最佳NRR催化剂表现出与中间体的中等结合强度。在所研究的金属掺杂的COFs中，配位数为3的Fe金属中心表现出最高的理论起始电位（-0.49 eV vs计算氢电极）。电荷密度和态密度分析表明，在该催化剂中，Fe 3d轨道与N-N键π* 轨道之间存在适度的π反馈和σ反馈，从而使中间体的结合强度达到最佳.
The electrocatalytic N2reduction reaction (NRR) is one of the most promising methods for the on-site and on-demand production of NH3. Single-metal-atom-doped covalent organic frameworks (COFs) are expected to function as efficient NRR electrocatalysts because a designed coordination environment of metal centers is available as a consequence of the wide range of possible designs of COFs. Herein, we used density functional theory (DFT) to systematically investigate the theoretical NRR activity of various single-3d-metal atoms doped into COFs with different coordination numbers to attain a general design guideline for the development of efficient NRR catalysts. The adsorption strength of NRR intermediates decreased as either the coordination number or the number of d-electrons of the metal centers increased. The potential-determining step switched between N–N bond activation and NH3desorption depending on the adsorption strength of the NRR intermediates. Therefore, an optimal NRR catalyst exhibits a moderate binding strength with intermediates. Among the investigated metal-doped COFs, an Fe metal center with a coordination number of three exhibited the highest theoretical onset potential (−0.49 eV vs the computational hydrogen electrode). In this catalyst, the charge-density and density-of-state analyses revealed moderate π back-donation and σ donation between Fe 3d orbitals and the π* orbital of N–N bonds, which resulted in the optimal binding strength of intermediates.