Two-Dimensional Metal–Organic Frameworks as Ultrahigh-Performance Electrocatalysts for the Fuel Cell Cathode: A First-Principles Study

Abstract

Except for metal−organic frameworks (MOFs) with traditional metal− nitrogen sites, MOFs with metal−oxygen sites may also possess good oxygen reduction reaction (ORR) catalytic activity due to their unique electronic structures. Herein, using density functional theory methods, the ORR performances of a series of M 3 (HHTT) 2 (where M is a 3d, 4d, or 5d transition metal and HHTT is 2,3,7,8,12,13hexahydroxytetraazanaphthotetraphene)) catalysts are explored. The binding energy (ΔE species ) results suggest that the binding energy of *OH (ΔE *OH ) shows a good linear relationship with the binding energies of *O and *OOH (ΔE *O and ΔE *OOH , respectively), indicating that ΔE *OH can serve as a descriptor to reflect the catalytic activity of M 3 (HHTT) 2 . In addition, the volcano plot suggests that M 3 (HHTT) 2 catalysts with a moderate binding strength of the intermediate *OH (0.6 eV < ΔE *OH < 0.9 eV) show relatively high ORR activity. Therefore, four highly active ORR catalysts are screened out, namely, Fe 3 (HHTT) 2 , Co 3 (HHTT) 2 , Rh 3 (HHTT) 2 , and Ir 3 (HHTT) 2 , which possess very small overpotentials of 0.35, 0.24, 0.31, and 0.29 V, respectively. Their potential-determining step is the reduction of O 2 to the intermediate *OOH. It is encouraging that the theoretically lowest overpotential of this kind of catalyst is 0.21 V, which is superior to that on Pt(111). Moreover, Co 3 (HHTT) 2 has excellent poisoning-tolerance ability for impurity gases (CO, NO, and SO 2 ) as well as fuel molecules (CH 3 OH and HCOOH).

Evaluating the Oxygen Electrode Reactions of La Single-Atom Catalysts with the N/C Coordination Effect

“…There is a certain scaling relationship between the adsorption of intermediates and the catalytic activity of the catalyst. For the ORR, when Δ E *OH is less than about –2.5 eV, ORR activity becomes better as the adsorption weakens. − It can be seen that LaN 4 C 2 –III/IV@Gra exhibits weaker OH adsorption in comparison with others, implying better ORR activity. Also, they exhibit appropriate adsorption strength for O 2 , making the OER reaction products more easily desorbed, thus potentially possessing excellent bifunctional activity.…”

Construction of a CoNiHHTP MOF/PHI Z-Scheme Heterojunction for ppb Level NO2 Photoelectric Sensing with 405 nm Irradiation at RT

“…18 For NiHHTP, peaks at 4.7, 9.6, and 12.6°r epresent the (100), (200), and (210) planes, respectively, and a peak at 27.8°denotes the (001) plane of the stacked structure: CoNiHHTP shows consistent results (Figure S8a). 45,46 The close matching interplanar distances of PHI and MHHTP's π−π stacking (0.32 and 0.33 nm, respectively) imply that they can be interactively stacked. 18,29,31 The broadened and shifted (002) peak of PHI in NiHHTP/PHI and CoNiHHTP/PHI points toward potential π−π interactions (Figure 1f).…”

Spin-Gapless Semiconductors and Quantum Anomalous Hall Effects of Tetraazanaphthotetraphene-Based Two-Dimensional Transition-Metal Organic Frameworks on Spintronics and Electrocatalysts for CO2 Reduction

“…Dou et al 22 successfully fabricated 200 μm atomically precise large singlecrystal 2D M 3 (HHTT) 2 (M = Cu and Ni), which exhibits high in-plane conductivity. Chen et al 23 reported that M 3 (HHTT) 2 (M = Fe, Co, Rh, and Ir) exhibits high oxygen reduction reaction activity based on first-principles calculations. Liu et al 24 reported a strong dependence between metal centers and the nitrogen-rich ligands on the electrocatalytic performance.…”