Rational Design of Electrocatalysts Comprising Single-Atom-Modified Covalent Organic Frameworks for the N₂ Reduction Reaction: A First-Principles Study

Abstract

The electrocatalytic N2 reduction 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 NH3 desorption 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.

Two-Dimensional Metal–Organic Framework Acts as a Hydrogen Evolution Cocatalyst for Overall Photocatalytic Water Splitting

“…Free-energy diagrams were obtained using the computational hydrogen electrode (CHE) model, following the same method described in previous reports. 32,33 Zero-point energy, entropy, and solvation corrections were applied based on reported values. 32,34 ■ RESULTS AND DISCUSSION Pretreatment of NiBHT.…”

Molybdenum Atom-Mediated Salphen-Based Covalent Organic Framework as a Promising Electrocatalyst for the Nitrogen Reduction Reaction: A First-Principles Study

“…1,38−40 COFs as electrocatalysts for NRR are still in their infancy and there are only a few reports of COFs as electrocatalysts for NRR in the literature. 1,41,42 In the pursuit of suitable electrocatalysts for NRR based on COFs, we performed density functional theory (DFT)-based computations on a molybdenum atom-doped salphen-based covalent organic framework (Mo-salphenCOF). Our calculations suggest that Mo-salphenCOF is both thermodynamically and electrochemically stable.…”

“…(iii) The catalytic activity of COFs can be tuned by changing the organic building blocks and the embedded transition metal atoms. (iv) The fully π-conjugated structure of COFs provides conducting channels, which assist in fast charge transport. ,− COFs as electrocatalysts for NRR are still in their infancy and there are only a few reports of COFs as electrocatalysts for NRR in the literature. ,, …”

Hexagonal MBene (Hf2BO2): A Promising Platform for the Electrocatalysis of Hydrogen Evolution Reaction

“…5 Nowadays, the efficiency and stability of catalyst have been the key factors of restricting widespread application of HER. 6 Benefited from the high specific surface area and unique electronic structure, 2-D electrocatalysts have drawn increasing attention, such as g-C 3 N 4 , 7 graphene, 8 MoS 2 , 9 COFs, 10 and MXenes. 11 Since Naguib et al 12 first synthesized 2-D transition metal carbon/nitride materials (MXenes) in 2011, MXenes have attracted substantial interests and have been widely studied both experimentally and theoretically.…”

“…Nowadays, the efficiency and stability of catalyst have been the key factors of restricting widespread application of HER . Benefited from the high specific surface area and unique electronic structure, 2-D electrocatalysts have drawn increasing attention, such as g-C 3 N 4 , graphene, MoS 2 , COFs, and MXenes …”