Nitrogen-Doped Graphene-Rich Catalysts Derived from Heteroatom Polymers for Oxygen Reduction in Nonaqueous Lithium–O₂ Battery Cathodes

Abstract

In this work, we present a synthesis approach for nitrogen-doped graphene-sheet-like nanostructures via the graphitization of a heteroatom polymer, in particular, polyaniline, under the catalysis of a cobalt species using multiwalled carbon nanotubes (MWNTs) as a supporting template. The graphene-rich composite catalysts (Co-N-MWNTs) exhibit substantially improved activity for oxygen reduction in nonaqueous lithium-ion electrolyte as compared to those of currently used carbon blacks and Pt/carbon catalysts, evidenced by both rotating disk electrode and Li-O(2) battery experiments. The synthesis-structure-activity correlations for the graphene nanostructures were explored by tuning their synthetic chemistry (support, nitrogen precursor, heating temperature, and transition metal type and content) to investigate how the resulting morphology and nitrogen-doping functionalities (e.g., pyridinic, pyrrolic, and quaternary) influence the catalyst activity. In particular, an optimal temperature for heat treatment during synthesis is critical to creating a high-surface-area catalyst with favorable nitrogen doping. The sole Co phase, Co(9)S(8), was present in the catalyst but plays a negligible role in ORR. Nevertheless, the addition of Co species in the synthesis is indispensable for achieving high activity, due to its effects on the final catalyst morphology and structure, including surface area, nitrogen doping, and graphene formation. This new route for the preparation of a nitrogen-doped graphene nanocomposite with carbon nanotube offers synthetic control of morphology and nitrogen functionality and shows promise for applications in nonaqueous oxygen reduction electrocatalysis for Li-O(2) battery cathodes.

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

“…In addition, the pyrrolic form of nitrogen (399.5 eV) observed at the N 1s spectrum of Fe‐N‐rGO‐800 °C is assigned to nitrogen atoms in a pentagon structure 11, 13, 31, 33. Pyrrolic nitrogen has been shown to decompose at temperatures above 800 °C to either pyridinic or graphitic nitrogen 31, 33, 34, 35. The successful replacement of carbon atoms inside of the graphitic lattice (graphitic N) with nitrogen is often connected with ORR active sites,36 however, incorporation of nitrogen at the center of graphitic sheets has only recently been correlated with enhanced onset potential during the ORR due to significant changes of electron distribution on carbon planes 37, 38.…”

Size-controlled large-diameter and few-walled carbon nanotube catalysts for oxygen reduction

“…44 The graphitic nitrogen content in Mn-derived carbon clots (60%) is notably higher than that in Fe, Co and Ni-derived carbon nanotubes, which were all nearly identical (54-55%). In ESI Fig.…”

Recent Progress in Electrocatalyst for Li‐O2 Batteries

“…As a benefit, a powerful electrocatalyst with enhanced catalytic activity can be obtained after nitrogen doping, which is verified experimentally. [52][53][54][55] In this aspect, several kinds of nitrogen doping materials including N-doped GNSs, [52] nitrogen-doped graphene with sheet-like nanostructure, [53] and nitrogen-doped, onion-like carbon, [54] are reported. All of these researches have exhibited an improvement of varying extent after nitrogen doping.…”