Stable Co/N-Doped Carbon Nanotubes as Catalysts for Oxygen Reduction

Abstract

It is an urgent and difficult task to develop low-cost, high-performance catalysts for the oxygen reduction reaction (ORR) to overcome the inherent defects of platinum-based catalysts, including low abundance, high cost, poor stability, and poor methanol tolerance. In this study, N-doped carbon nanotubes (N-CNTs) and Co/N-CNT catalysts are synthesized by grinding and subsequent calcination, and the whole process does not require strict control of the reaction conditions, thus greatly simplifying the synthesis route of the catalysts. The unique structure, in which Co nanoparticles are evenly embedded in the tube and tip of CNTs, exhibits outstanding ORR performance and electrochemical stability as a result of the Co–CNT interactions. Furthermore, due to the catalytic graphitization ability of Co nanoparticles, a high graphitization degree, large specific surface area, and abundant pore structure are achieved by adjusting the calcination temperature, thus accelerating electron transfer and oxygen diffusion. The optimized catalyst, calcined at 750 °C (Co/N-CNT-750), exhibits better ORR activity and excellent methanol tolerance in alkaline media, indicating its great potential for large-scale application in storage technologies.

PtRuFe/Carbon Nanotube Composites as Bifunctional Catalysts for Efficient Methanol Oxidation and Oxygen Reduction

“…In addition, the Tafel slopes of various catalysts were calculated so as to assess the catalytic kinetics, as depicted in Figure c–f. The Tafel slope of the Pt/CNT catalyst is 71.3 mV dec –1 , and the Tafel slopes of binary and ternary catalysts are significantly less than those of Pt/CNT and JM-Pt/C we previously reported. , Especially the PtRuFe/CNT catalyst shows the smallest Tafel slope of 36.1 mV dec –1 , implying its fastest catalytic kinetics. Figure g,h depicts the mass and specific activities of the catalysts, and JM-Pt/C was used for comparison.…”

“…The Tafel slope of the Pt/CNT catalyst is 71.3 mV dec −1 , and the Tafel slopes of binary and ternary catalysts are significantly less than those of Pt/CNT and JM-Pt/C we previously reported. 48,55 Especially the PtRuFe/CNT catalyst shows the smallest Tafel slope of 36.1 mV dec −1 , implying its fastest catalytic kinetics. Figure 7g,h , respectively, which may be attributed to the following points.…”

Intrinsic Carbon Defects in Nitrogen and Sulfur Doped Porous Carbon Nanotubes Accelerate Oxygen Reduction and Sulfur Reduction for Electrochemical Energy Conversion and Storage

“…heteroatom doping in carbon matrices. ,,− The generation of extrinsic defects can regulate the electronic structure, create plenty of unsaturated sites, and hence offer preferable active centers for accelerating electrochemical kinetics. For example, He et al synthesized Co/N doped carbon nanotubes (CNTs) by grinding and subsequent calcination, which showed remarkable ORR performance . Incorporation of nitrogen (N) atoms with stronger chemical polarity can attract electrons from adjacent carbon atoms and cause the formation of positively charged centers, thus availing oxygen chemisorption and electron transfer. , Pyridinic N not only enhances the adsorption of O 2 and subsequent breaking of the O–O bond but also offers numerous bonding sites for anchoring polysulfides, consequently boosting the reaction kinetics of both the ORR and SRR processes.…”

S/N codoped carbon nanotubes as an efficient ORR electrocatalyst for zinc–air batteries

“…), the surface of carbon nanotubes can be loaded with hydrophilic functional groups such as hydroxyl, carbonyl, and carboxyl, and then through functional group modication and heteroatom doping, their surface structure can be changed and their catalytic performance can be further improved. [31][32][33][34] A. Pendashteh et al constructed a highly bifunctional air catalyst from macroscopic CNT bers (CNTfs) through direct CVD spinning followed by a hydrothermal method. 35 The electrocatalytic properties of the samples were tuned by altering nitrogen doping and defect densities which can be readily adjusted by using different hydrothermal reaction temperatures.…”