Nitrogen-Doped Graphene Oxide Electrocatalysts for the Oxygen Reduction Reaction

Abstract

Platinum group metal-free (PGM-free) electrocatalysts for the oxygen reduction reaction (ORR) often exhibit a complex functionalized graphitic structure. Because of this complex structure, limited understanding exists about the design factors for the synthesis of high-performing materials. Graphene, a two-dimensional hexagonal structure of carbon, is amenable to structural and functional group modifications, making it an ideal analogue to study crucial properties of more complex graphitic materials utilized as electrocatalysts. In this paper, we report the synthesis of active nitrogen-doped graphene oxide catalysts for the ORR in which their activity and four-electron selectivity are enhanced using simple solvent and electrochemical treatments. The solvents, chosen based on Hansen’s solubility parameters, drive a substantial change in the morphology of the functionalized graphene materials by (i) forming microporous holes in the graphitic sheets that lead to edge defects and (ii) inducing 3D structure in the graphitic sheets that promotes ORR. Additionally, the cycling of these catalysts has highlighted the multiplicity of the active sites, with different durability, leading to a highly selective catalyst over time, with a minimal loss in performance. High ORR activity was demonstrated in an alkaline electrolyte with an onset potential of ∼1.1 V and half-wave potential of 0.84 V vs RHE. Furthermore, long-term stability potential cycling showed minimal loss in half-wave potential (<3%) in both N2- and O2-saturated solutions with improved selectivity toward the four-electron reduction after 10000 cycles. The results described in this work provide additional understanding about graphitic electrocatalysts in alkaline media that may be utilized to further enhance the performance of PGM-free ORR electrocatalysts.

Cobalt Nanoparticles on Plasma-Controlled Nitrogen-Doped Carbon as High-Performance ORR Electrocatalyst for Primary Zn-Air Battery

“…One of the most typical methods is to synthesize a catalyst using a heteroatom-doped carbon matrix [12,13]. Among them, nitrogen-doped (N-doped) carbon represents a far better performance compared with pristine carbon support [14][15][16][17][18]. The catalyst often shows relatively high catalytic performance in alkaline electrolytes.…”

Graphene-Modified Composites and Electrodes and Their Potential Applications in the Electro-Fenton Process

“…The doping of graphene/rGO, using heteroatoms such as N, B, P and Fe, has been widely studied for the development of catalysts for the oxygen reduction reaction [106,107]. Depending on the preparation conditions employed and the nature of the dopants selected, the mechanism can vary from a two-electron to a four-electron pathway.…”

Amino-1H-tetrazole-regulated high-density nitrogen-doped hollow carbon nanospheres for long-life Zn–air batteries

“…To achieve maximum usage efficiency of catalysts, the fourelectron transfer pathways of N-doped carbon nanostructures are the most desirable alternatives to Pt catalysts. [30][31][32][33][34] Many efforts have been devoted to developing high-level N-doping (mainly using Gr N and Pr N) porous carbons able to catalyze the ORR via direct, four-electron transfer pathways. [35][36][37][38] For better evaluating the catalyst containing Gr N and Pr N, the following two factors must be ensured: (1) high-level N-doping guarantees catalytic activity for the ORR; (2) precisely tunable content of Gr N and Pr N is used to explore well-dened doped active sites in carbon frameworks.…”