Cobalt‐Embedded Nitrogen‐Doped Carbon Nanotubes as High‐Performance Bifunctional Oxygen Catalysts

Abstract

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key processes in various renewable‐energy technologies and call for high‐performance bifunctional ORR/OER electrocatalysts. In this study, a highly efficient bifunctional oxygen catalyst, which was made of bamboo‐like nitrogen‐doped carbon nanotubes with embedded cobalt nanoparticles (Co@NCNTs), was fabricated by a one‐step pyrolysis route. Systematic electrochemical results demonstrated that the optimized electrocatalyst only needed a small potential hysteresis of about 0.834 V to achieve 1 mA cm−2 ORR current and 10 mA cm−2 OER current, and simultaneously gave superior stability and methanol tolerance to those of commercial metal catalysts. The major factors that influenced the bifunctional catalyst performance of Co@NCNTs are discussed, among which the nitrogen chemical state and metal element play important roles. Moreover, the catalyst showed good activity and stability in rechargeable zinc–air batteries, which indicated their potential applications in metal–air batteries, fuel cells, and water‐splitting devices.

Plant Oil–Inspired 3D Flower‐Like Zn3V3O8 Nanospheres Coupled with N‐Doped Carbon as Anode Material for Li‐/Na‐Ion Batteries

“…Two peaks near 399.8 and 400.6 eV of the N XPS spectrum in Figure e correspond to N—C—N/N—H bonds deriving from the introduction of soybean oil. Relative researches have proved that doping a small amount of nitrogen in active materials can significantly enhance the conductivity, thus improving the electrochemical performances . As depicted in Figure f, the C 1s spectrum is composed of four peaks after refined fitting, the peak at 284.6 eV represents the sp 2 ‐bond carbon (C═C) signal, which was on account of the incompletely carbonizing SDBS during the synthetic process.…”

“…As shown in Figure f, during the whole charge–discharge process, the capacity curve of B‐SZVO maintains a relatively more stable and higher level than that of S‐SZVO. In addition, the capacity increases in the initial 200 cycles, which is probably ascribed to the activation of electrode materials or interfacial storage of lithium ions . With the increase in cycle number, more active materials can be exposed to lithium storage, and the increase of interfaces can also contribute to the storage of lithium ions.…”

Reducing the Cost of Zinc–Oxygen Batteries by Oxygen Recycling

“…Vanadium redox flow and lithium‐ion batteries encounter drawbacks of high cost and/or poor safety, although they have been developed rapidly in China. Among a great variety of technologies, zinc–air/oxygen batteries have attracted considerable interest as possible candidates for energy‐storage solutions due to their low cost, abundant reserves, and good safety . However, much fewer zinc–air/oxygen systems have been developed in recent years because the cyclic performance and energy efficiency are still unsatisfactory, which has led to a great increment in capital (one‐time setup costs) and running costs.…”

“…Hao et al. synthesized Co@nitrogen‐doped carbon nanotubes (NCNTs) with better activity; the voltage gap decreased to 0.81 V at 5 mA cm −2 . The CoO 0.87 S 0.13 /nitrogen‐doped graphene nanomesh (GN) catalyst developed by Chen and co‐workers showed stable cycling over 320 h, with a voltage gap of 0.77 V at 20 mA cm −2 .…”

In Situ Decorating Coordinatively Unsaturated Fe Sites for Boosting Water Oxidation Performance of TiO2 Photoanode

“…Among these catalysts, RuO 2 and IrO 2 as the representative OER catalysts have exhibited the excellent catalytic performance toward water oxidation, but the expensive cost and deficiency greatly limit its widespread application . Therefore, countless efforts have been devoted to fabricate the efficient and alternative OER cocatalysts to improve the PEC water splitting efficiency, such as transition metal oxides, metallic hydroxides, and C‐doped nanomaterials . Among these materials, the hot topic of metallic hydroxides in the field of catalysis has demonstrated that some metal atoms could show excellent OER catalytic activity, which results from the abundant metal sites acted as the active center .…”