Metal–Organic Framework‐Derived Bamboo‐like Nitrogen‐Doped Graphene Tubes as an Active Matrix for Hybrid Oxygen‐Reduction Electrocatalysts

Abstract

In this work, large size (i.e., diameter > 100 nm) graphene tubes with nitrogen-doping are prepared through a high-temperature graphitization process of dicyandiamide (DCDA) and Iron(II) acetate templated by a novel metal-organic framework (MIL-100(Fe)). The nitrogen-doped graphene tube (N-GT)-rich iron-nitrogen-carbon (Fe-N-C) catalysts exhibit inherently high activity towards the oxygen reduction reaction (ORR) in more challenging acidic media. Furthermore, aiming to improve the activity and stability of conventional Pt catalysts, the ORR active N-GT is used as a matrix to disperse Pt nanoparticles in order to build a unique hybrid Pt cathode catalyst. This is the first demonstration of the integration of a highly active Fe-N-C catalyst with Pt nanoparticles. The synthesized 20% Pt/N-GT composite catalysts demonstrate significantly enhanced ORR activity and H(2) -air fuel cell performance relative to those of 20% Pt/C, which is mainly attributed to the intrinsically active N-GT matrix along with possible synergistic effects between the non-precious metal active sites and the Pt nanoparticles. Unlike traditional Pt/C, the hybrid catalysts exhibit excellent stability during the accelerated durability testing, likely due to the unique highly graphitized graphene tube morphologies, capable of providing strong interaction with Pt nanoparticles and then preventing their agglomeration.

Atomically Dispersed Fe‐Nx/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

“…In contrast, the SEM image of the Fe-N sample prepared in the absence of SA ( Figure S1c, Supporting Information) reveals numerous metal agglomerations even after acid leaching, indicating that the introduction of SA could substantially protect Fe ions from aggregation during pyrolysis. Interestingly, no bamboo-like N-doped carbon nanotubes could be observed in our SA-Fe-N catalysts, which were commonly obtained when CN was used as a N precursor in previous reports [31,32] and also in the Fe-N-KJ control sample ( Figure S2, Supporting Information). Transmission electron microscopy (TEM) image of SA-Fe-N-1.5-800 ( Figure S3a, Supporting Information) displays the crumpled sheet-like structure.…”

Metal‐Organic Framework‐Based Nanomaterials for Electrocatalysis

“…MIL-100 (Fe) was identified first as an efficient template for the growth of highly active bamboo-like N-doped CNTs loaded with Fe/ Fe 3 C (N-GT) catalysts. [71] Subsequently, Pt particles with an average particle size of 3-4 nm were loaded onto the N-GTs (Pt/N-GTs) using a simple solution reduction method. The smaller-sized Pt particles ensured maximum exposure of Pt atoms to the electrolyte and the O 2 species.…”

High‐Performance Direct Methanol Fuel Cells with Precious‐Metal‐Free Cathode

“…Among the studied formulations, iron‐nitrogen‐carbon (Fe‐N‐C) catalysts are the most promising in terms of their activity and stability in more challenging acidic electrolytes 11, 12, 13, 14, 15. To date, even though substantial progress has been achieved in improving the performance of such‐synthesized Fe‐N‐C catalysts,16, 17, 18 their current activity in H 2 ‐air fuel cell is still not comparable to Pt cathode 19. Practical applications of NPMCs in H 2 fuel cells still have a long way to go.…”