Carbon Anode in Carbon History

This study examines how the several major industries, associated with a carbon artifact production, essentially belong to one, closely knit family. The common parents are the geological fossils called petroleum and coal. The study also reviews the major developments in carbon nanotechnology and electrocatalysis over the last 30 years or so. In this context, the development of various carbon materials with size, dopants, shape, and structure designed to achieve high catalytic electroactivity is reported, and among them recent carbon electrodes with many important features are presented together with their relevant applications in chemical technology, neurochemical monitoring, electrode kinetics, direct carbon fuel cells, lithium ion batteries, electrochemical capacitors, and supercapattery.

Effect of Heteroatoms in Ordered Microporous Carbons on Their Electrochemical Capacitance

Micropores play a more important role in enhancing the electrochemical capacitance than mesopores and macropores; therefore, the effect of heteroatom doping into micropores on the electrochemical behavior is interesting. However, heteroatom doping into porous carbon materials would potentially change their pore structures and pore sizes, which also affect their electrochemical capacitive behaviors. To gain insight into the intrinsic effects of heteroatoms on the electrochemical capacitive behaviors, zeolite-templated carbon (ZTC) may be the most suitable candidate. ZTC is an ordered microporous carbon with a uniform micropore size of 1.2 nm, a high surface area, and a large micropore volume. In this work, a series of ZTCs containing oxygen, nitrogen, or boron as heteroatoms, with an ordered pore structure and the same pore size, are prepared. By examining their electrochemical capacitive behaviors in an organic electrolyte, the effect of heteroatom doping can be isolated and discussed without considering the effects of pore structure and pore size. Acid anhydride groups are found to generate pseudocapacitance in two potential ranges, -1.0 to -0.3 V (vs Ag/AgClO₄) and -0.2 to 0.4 V. B is introduced into the ZTC framework solely as -B(OH)₂, which is found to be an electrochemically inert species. N is introduced as pyridine (3.0%), pyridone/pyrrole (23.8%), quaternary (66.6%), and oxidized N (6.6%), and these species exhibit noticeable pseudocapacitance in the microporous carbon.

Templated nanocarbons for energy storage

The template carbonization method is a powerful tool for producing carbon materials with precisely controlled structures at the nanometer level. The resulting templated nanocarbons exhibit extraordinarily unique (often ordered) structures that could never be produced by any of the conventional methods for carbon production. This review summarizes recent publications about templated nanocarbons and their composites used for energy storage applications, including hydrogen storage, electrochemical capacitors, and lithium-ion batteries. The main objective of this review is to clarify the true significance of the templated nanocarbons for each application. For this purpose, the performance characteristics of almost all templated nanocarbons reported thus far are listed and compared with those of conventional materials, so that the advantages/disadvantages of the templated nanocarbons are elucidated. From the practical point of view, the high production cost and poor mass-producibility of the templated nanocarbons make them rather difficult to utilize; however, the study of their unique, specific, and ordered structures enables a deeper insight into energy storage mechanisms and the guidelines for developing energy storage materials. Thus, another important purpose of this work is to establish such general guidelines and to propose future strategies for the production of carbon materials with improved performance for energy storage applications.

Heat-Treatment and Nitrogen-Doping of Activated Carbons for High Voltage Operation of Electric Double Layer Capacitor

The electric double layer capacitor (EDLC) is considered to be one of the promising systems for electric energy storage. Both the optimization of the micropore structure of the activated carbon electrode and the higher voltage operation of the EDLC are necessary for improving the energy density of the EDLC. Thus, there are already many research examples related to the former. The author focused on the latter to achieve a breakthrough in the energy density. The author will introduce the recent results of the surface modification using nitrogen monoxide and the heat-treatment above 1000°C for the activated carbon electrode.

Enhancement mechanism of electrochemical capacitance in nitrogen-/boron-doped carbons with uniform straight nanochannels

Anodic aluminum oxide (AAO) with uniform straight nanochannels was completely coated with pure, N-doped, or B-doped carbon layer. Their electric double layer capacitances are measured in aqueous (1 M sulfuric acid) and organic (1 M Et4NBF4/polypropylene carbonate) electrolyte solutions in order to investigate the capacitance enhancement mechanisms caused by N- or B-doping. Since the three types of carbon-coated AAOs (pure, N-doped, or B-doped) have exactly the same pore structure, the observed capacitance enhancement was ascribable to only the following factors: (i) better wettability, (ii) the decrease of equivalent series resistance, (iii) the contribution of space-charge-layer capacitance, and (iv) the occurrence of pseudocapacitance. From the measurements of the wettability and the electrical resistance of the coated AAOs together with the electrochemical investigation (the cyclic voltammetry, the galvanostatic charge/discharge cycling, and the impedance analysis), it is concluded that the pseudocapacitance through faradic charge transfer (factor iv) is the most important factor to enhance the capacitance by N- or B-doping. This can be applied to not only the present carbon-coated AAOs but also any other porous carbons.