Mn Nanoparticles Encapsulated within Mesoporous Helical N‐Doped Carbon Nanotubes as Highly Active Air Cathode for Zinc–Air Batteries

Abstract

The practical application of clean energy conversion and storage technologies, such as fuel cells and metal-air batteries, have been significantly impeded by the high cost and scarcity of precious metal catalysts used for the oxygen reduction reaction (ORR). Transitional metal/carbon compounds are a promising alternative to precious metal catalysts for the ORR. Herein, Mn nanoparticles encapsulated within mesoporous helical N-doped carbon nanotubes (Mn@HNCNTs) are developed as highly active ORR catalysts. In terms of the onset potential and half-wave potential for ORR, the optimized Mn@HNCNTs exhibit an excellent ORR performance, which is comparable to Pt/C. When the Mn@HNCNTs are assembled as air cathodes, with zinc foil as the anode in primary zinc-air cells, the obtained cell delivers a higher cell voltage and capacity than the zinc-air cell using Pt/C as the air cathode, as well as many reported cells using TM/ CNT-based air cathodes. The electrocatalytic performance in the zinc-air cell demonstrates that Mn@HNCNTs have great potential for use as ORR catalysts in metal-air batteries.

A review of helical carbon materials structure, synthesis and applications

“…TEM image of helical carbon nanotube with a spiral diameter of 200 nm and a spiral distance of 440 nm is presented in Fig. 2h [41]. With a diameter of 50-60 lm, a 0.5-mm segment contains 7 loops, which has an average linear loop density of 14 per mm and a pitch of 60-70 mm, as shown in Fig.…”

“…HCMs were also used in catalysis, energy storage devices, solar cell, etc. Wang et al encapsulated Mn nanoparticles into mesoporous N-doped helical carbon nanotubes [41]. The composite material showed high oxygen reduction reaction (ORR) activity.…”

Recent Advances in Nanoscale Based Electrocatalysts for Metal-Air Battery, Fuel Cell and Water-Splitting Applications: An Overview

“…Materials 2022, 15, 458 9 of 23 that ORR is facilitated by the pyridinic N content, while OER is promoted by the surface contents of Co-Nx and Co 3+ /Co 2+ . Further, the rapidly developed Mn nanomaterial-based mesoporous helical structured N-doped carbon nanotube (Mn@HNCNT) composite has been reported to act as a precious metal catalyst for ORR [59]. The catalyst was fabricated via molten-salt method at high temperature.…”

Uniform Bamboo-like N-Doped Carbon Nanotubes Derived from a g-C3N4 Substrate Grown via Anchoring Effect to Boost the Performance of Metal–Air Batteries

“…6,7 Nitrogen-doped CNTs (N-CNTs) showed excellent electrocatalytic performance and durability under oxygen reduction reaction (ORR) conditions in alkaline media with significant potential as a promising alternative to state-of-the-art platinum group metal (PGM)based catalysts. 8,9 In these materials, C−C bonds are distorted due to the presence of heteroatoms in carbon matrices resulting in stronger interaction with oxygen molecules which facilitates the oxygen reduction process. 10 Incorporation of electron-donating nitrogen atoms in CNTs (N-CNTs) increases their conductivity and surface alkalinity, and, in combination with the enhancement of their surface hydrophilicity, 11 results in the formation of active sites.…”

“…The sustainable development of modern society can no longer be supported by scarce and nonrenewable traditional fossil energy sources. Many environmental problems caused by the use of fossil fuels force humanity to develop clean and sustainable energy technologies. − Nanostructured carbon materials exhibit excellent catalytic performance in many electrochemical reactions used for energy storage and conversion, , among them carbon nanotubes (CNTs) have attracted much research attention due to their typical layered hollow structure, large diameter, good mechanical strength, and excellent electrical conductivity. , Nitrogen-doped CNTs (N-CNTs) showed excellent electrocatalytic performance and durability under oxygen reduction reaction (ORR) conditions in alkaline media with significant potential as a promising alternative to state-of-the-art platinum group metal (PGM)-based catalysts. , In these materials, C–C bonds are distorted due to the presence of heteroatoms in carbon matrices resulting in stronger interaction with oxygen molecules which facilitates the oxygen reduction process . Incorporation of electron-donating nitrogen atoms in CNTs (N-CNTs) increases their conductivity and surface alkalinity, and, in combination with the enhancement of their surface hydrophilicity, results in the formation of active sites. − It was reported that doped nitrogen atoms in N-CNTs form active sites of the M–N x type (M = Fe, Co, Mn, Ni) encapsulated inside CNTs, further enhancing their electrocatalytic performance. − …”