Metal‐Triazolate‐Framework‐Derived FeN₄Cl₁ Single‐Atom Catalysts with Hierarchical Porosity for the Oxygen Reduction Reaction

Abstract

The construction of single-atom catalysts (SACs) with high single atom densities, favorable electronic structures and fast mass transfer is highly desired. We have utilized metaltriazolate (MET) frameworks, a subclass of metal-organic frameworks (MOFs) with high N content, as precursors since they can enhance the density and regulate the electronic structure of single-atom sites, as well as generate abundant mesopores simultaneously. Fe single atoms dispersed in a hierarchically porous N-doped carbon matrix with high metal content (2.78 wt %) and a FeN 4 Cl 1 configuration (FeN 4 Cl 1 /NC), as well as mesopores with a pore:volume ratio of 0.92, were obtained via the pyrolysis of a Zn/Fe-bimetallic MET modified with 4,5-dichloroimidazole. FeN 4 Cl 1 /NC exhibits excellent oxygen reduction reaction (ORR) activity in both alkaline and acidic electrolytes. Density functional theory calculations confirm that Cl can optimize the adsorption free energy of Fe sites to *OH, thereby promoting the ORR process. The catalyst demonstrates great potential in zinc-air batteries. This strategy selects, designs, and adjusts MOFs as precursors for high-performance SACs.

Macro/Micro‐Environment Regulating Carbon‐Supported Single‐Atom Catalysts for Hydrogen/Oxygen Conversion Reactions

“…FeN 4 Cl 1 /NC exhibited a more favorable thermodynamic reaction process for ORR due to the improved adsorption energy for OH* (Figure 8d-f). [103] Recent reports have demonstrated that the OH* could graft to FeN 4 dynamically during the ORR process, and the formed FeN 4 OH can act as the efficient active sites to facilitate the last step desorption of OH*, leading to enhanced ORR activity. [104,105] The OH* can also boost the catalytic activity of FeCoN 5 dual atom sites anchored on N-doped carbon electrocatalyst.…”

“…[99][100][101] For example, the halogen atom (Cl − ) coordinated with Fe-N 4 plane vertically (FeCl 1 N 4 ) has shown improved oxygen adsorption capacity, leading to boosted ORR performance. [102,103] Similarly, by the pyrolysis of metal (Zn/Fe)triazolate (MET) frameworks decorated with 4,5-dichloroimidazole, FeN 4 Cl 1 species anchored on N-doped porous carbon matrix (FeN 4 Cl 1 /NC) electrocatalyst was obtained (Figure 8a). FeN 4 Cl 1 /NC exhibited an outstanding ORR performance with a half-wave potential (E 1/2 ) of 0.91 V versus RHE in 0.1 m KOH (Figure 8b,c).…”

“…f) Free energy diagram of ORR on FeN 4 /NC and FeN 4 Cl 1 /NC (U = 0). Reproduced with permission [103]. Copyright 2021, Wiley-VCH.…”

Rational coordination regulation in carbon-based single-metal-atom catalysts for electrocatalytic oxygen reduction reaction

“…In the past couple of years, various SMACs have been therefore widely explored and showed encouraging electrocatalytic ORR activities [ 29 – 32 ]. The high intrinsic activity of isolated metal sites and the low cost of component elements in SMACs make these catalysts promising candidates to substitute traditional noble metal-based ORR catalysts [ 33 – 37 ]. Particularly, carbon-based SMACs exhibit the state-of-the-art electrocatalytic ORR activities, and have been accordingly recognized as an emerging type of ORR catalysts for potential practical applications in fuel cells and metal-air batteries [ 38 – 41 ].…”

Metal–Organic Frameworks-Mediated Assembly of Gold Nanoclusters for Sensing Applications

“…On account of the periodic porosity and tunable structural characteristic, versatile functionality, chemical/thermal stability, and high surface area, MOFs hold great potential as multifunctional platforms for theranostics [ 44 – 46 ], catalysis [ 47 , 48 ], gas storage and separation [ 49 , 50 ], energy storage and conversion [ 51 , 52 ], optoelectronics [ 53 , 54 ], etc. Significantly, due to the distinct characteristics of tunable luminescence [ 55 ], optical absorbance [ 56 ], conductivity [ 57 ], and catalytic activity [ 58 , 59 ], MOFs have also been widely exploited for the development of various sensors in recent years [ 60 – 64 ].…”