Chemically Functionalized Carbon Nanotubes with Pyridine Groups as Easily Tunable N-Decorated Nanomaterials for the Oxygen Reduction Reaction in Alkaline Medium

Abstract

We report on the N-decoration of multiwalled carbon nanotubes (MWCNTs) via chemical functionalization under mild reaction conditions. The introduction of tailored pyridinic functionalities as N-containing edge-type group mimics generates effective catalysts for the oxygen reduction reaction (ORR) in an alkaline environment. The adopted methodology lists a number of remarkable technical advantages, among which is an easy tuning of the electronic properties of N-containing groups. The latter aspect further increases the level of complexity for the rationalization of the role of the N-functionalities on the ultimate electrochemical performance of the as-prepared metal-free catalysts. Electrochemical outcomes crossed with the computed electronic charge density distributions on each scrutinized pyridine group have evidenced the central role played by the N-chemical environment on the final catalyst performance. Notably, small variations of the atomic charges on the N-proximal carbon atoms of the chemically grafted heterocycles change the overpotential values at which the oxygen reduction reaction starts. The protocol described hereafter offers an excellent basis for the development of more active metal-free electrocatalysts for the ORR. Finally, the asprepared catalytically active materials represent a unique model for the in-depth understanding of the underlying ORR mechanism.

Carbon Nitrogen Nanotubes as Efficient Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions

“…54 A lot of experimental results prove pyridinic-N is ORR active. 27,28,43,55,56 In our case, the pyrrolic-N is excluded as the most active site due to the observation that the activity increases with the decrease of pyrrolic-N atomic content ( Figure 4b). Our results shows that the primary activity comes from both graphitic-N and pyridinic-N but we can't distinguish between them, because the trend is similar showing the ORR activity increases with the increase of graphitic-N and pyridinic-N atomic content except for CNNT-ACN (Figure 4b).…”

Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions

“…Based on this fundamental concept, the chemical functionalization becomes an alternative and effective approach to introducing N into complex carbon nanostructures [80]. Accordingly, Tuci et al reported a systematic study on the synthesis, characterization, and electrocatalytic property of MWCNTs functionalized with a series of well-defined pyridine groups [81]. They also discussed the role of the electronic charge density distribution at the chemically grafted N heterocycles on the ORR performance.…”

Hybrid of Fe@Fe3O4 core-shell nanoparticle and iron-nitrogen-doped carbon material as an efficient electrocatalyst for oxygen reduction reaction

“…However, as one of the scarcest noble metals on Earth, the major concern for all existing and emerging applications built upon Pt is its limited availability and high cost [5]. In addition, Pt-based electrocatalysts suffer from other limiting factors, such as declining activity caused by methanol poisoning and instability under extreme electrochemical condition [6]. As a result, intensive research efforts have been focused on developing non-precious metal-based or metal-free ORR electrocatalysts with high activity comparable to Pt and superior stability [7,8].…”