Shape Fixing via Salt Recrystallization: A Morphology-Controlled Approach To Convert Nanostructured Polymer to Carbon Nanomaterial as a Highly Active Catalyst for Oxygen Reduction Reaction

Abstract

Herein, we report a "shape fixing via salt recrystallization" method to efficiently synthesize nitrogen-doped carbon material with a large number of active sites exposed to the three-phase zones, for use as an ORR catalyst. Self-assembled polyaniline with a 3D network structure was fixed and fully sealed inside NaCl via recrystallization of NaCl solution. During pyrolysis, the NaCl crystal functions as a fully sealed nanoreactor, which facilitates nitrogen incorporation and graphitization. The gasification in such a closed nanoreactor creates a large number of pores in the resultant samples. The 3D network structure, which is conducive to mass transport and high utilization of active sites, was found to have been accurately transferred to the final N-doped carbon materials, after dissolution of the NaCl. Use of the invented cathode catalyst in a proton exchange membrane fuel cell produces a peak power of 600 mW cm(-2), making this among the best nonprecious metal catalysts for the ORR reported so far. Furthermore, N-doped carbon materials with a nanotube or nanoshell morphology can be realized by the invented method.

N-doped carbon nanotubes containing a high concentration of single iron atoms for efficient oxygen reduction

“…To the best of our knowledge, our CNT@Fe-N-PC catalyst showed the best ORR performance in an acidic medium compared with all previously reported Fe-N-C and other non-noble-metal catalysts (Supplementary Table 2). 11,12,13,20,22,27,28,31,[37][38][39][40] In addition to the high activity, we further studied the durability of the CNT@Fe-N-PC catalyst. Figure 3c shows that the current density decay is 12% after 40 000 s of testing, much smaller than that (57%) of commercial Pt/C.…”

“…26 Most importantly, the performance of the catalyst obtained is still unsatisfactory, that is, the overpotential versus a commercial Pt/C catalyst is generally more than 60 mV. 20,27,28 In this study, we developed a simple and scalable atomic isolation technique for synthesizing a porous Fe-N-C catalyst with a high concentration of N-coordinated single Fe atoms by pyrrole polymerization on carbon nanotubes (CNTs), followed by Fe 3+ and Zn 2+ (or Li + , Na + and K + ) ion adsorption, and finally one-step pyrolysis. The resulting catalyst is denoted CNT@Fe-N-PC.…”

Rational Design and Synthesis of Low-Temperature Fuel Cell Electrocatalysts

“…16c produced a measured area current activity of 9.9 mA cm −2 at 0.9 V iR-free and a peak power density of 0.9 W cm −2 . Other framework substrate methods, such as a combination of various carbon materials [164][165][166] and synthesis with silica template [131,167,168] or NaCl template [169], were also found to create abundant channels/pores to facilitate mass transportation.…”

Surfactant-Template Preparation of Polyaniline Semi-Tubes for Oxygen Reduction

“…The multi-technique characterization have suggested that the enviable performance should be ascribed to the formation of metal-N complexion structures as well as the carbon nanostructures such as thin graphene sheets and nanofibers [10][11][12]. It has been generally accepted that the formation of uniform and ordered carbon nanostructures is very important in enhancing the catalytic activity [10][11][12][13][14][15][16][17][18][19].…”