Sulfur–nitrogen co-doped three-dimensional carbon foams with hierarchical pore structures as efficient metal-free electrocatalysts for oxygen reduction reactions

Abstract

Despite the good progress in developing doped carbon catalysts for oxygen-reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing new metal free doped carbon materials with abundance active sites as well as excellent electron transfer and reactant transport rate towards ORR may be a potential solution. Herein, we develop a novel three-dimensional (3D) sulfur-nitrogen co-doped carbon foams (S-N-CF) with hierarchical pore structures, using a convenient, economical, and scalable method. The experimental results have demonstrated that the obtained 3D S-N-CF exhibited better catalytic activity, longer-term stability and higher methanol tolerance than a commercial Pt/C catalyst. Such excellent performances may be attributed to the synergistic effect, which includes high catalytic sites for ORR provided by high S-N heteroatom loading, excellent reactant transport caused by hierarchical pore structures and high electron transfer rate provided by 3D continuous networks. Our results not only develop a new type of catalysts with excellent electrocatalytic performance by a commercially valid route, but also provide useful information for further clarification of the relationship between the microstructures of metal-free carbon materials and catalyst properties for ORR. More importantly, the idea to design hierarchical pore structures could be applied to other catalytic materials and serve as a general strategy for improving the activity of various ORR catalysts.

Doping carbons beyond nitrogen: an overview of advanced heteroatom doped carbons with boron, sulphur and phosphorus for energy applications

“…139 Most recently also S-and N-codoped carbon foams were synthesised by Huang et al The foams exhibit a continuous and hierarchical structure and also show promising results as ORR catalysts. 140 The eld of S-N-codoped carbons thus represents a thriving area of materials research, and numerous studies can be expected in the near future, contributing to a quick progress and development. Meanwhile, another synthetic approach, based on nitrile functionalised thiazolium salts, has been published, showing a novel concept allowing for an easy tuning of both nitrogen and sulphur contents, simply by a variation of the carbonisation temperature.…”

Three-Dimensional Heteroatom-Doped Nanocarbon for Metal-Free Oxygen Reduction Electrocatalysis: A Review

“…Up to now, various 3D porous carbon materials have been exploited as promising and efficient catalysts for their outstanding virtues such as low cost, high conductivity, high surface area with abundant porosity, designable carbon framework, as well as high chemical and mechanical stability [100][101][102][103]. Similar to 3D CNTs and 3D graphene, 3D porous carbon can also be doped with heteroatoms for ORR electrocatalysts [104].…”

Emerging methanol-tolerant AlN nanowire oxygen reduction electrocatalyst for alkaline direct methanol fuel cell

“…The transition metal nitride catalysts also displayed methanol-tolerance for ORR reactions. In comparison with a sharp ORR current decrease of ,80% for commercial Pt/C catalyst after the addition of a 3 M methanol at 90 s in the LSV test, it was reported that a sulfur-nitrogen Co-doped carbon foam catalyst has no noticeable decrease under the same test condition 23 . The similar behavior was also found for sulfur-nitrogen Co-doped graphene oxide 24 and Co-doping carbon blacks with nitrogen-fluorine 25 .…”

“…This discovery reveals a new type of metal nitride ORR catalyst that can be cheaply produced from crystal growth method. D irect methanol fuel cell (DMFC) is one of the most attractive power sources for portable and vehicular applications due to the simplicity of the system and the adaptability of the liquid fuel 1,2 . At present, the commercialization of DMFCs is hindered by several issues, including crossover of methanol from anode to cathode 3,4 , as well as the dependence on precious Pt catalyst for methanol oxidation and oxygen reduction reactions 5,6 .…”