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This study aims to elucidate the role of hydrogen desorption profiles obtained through temperature programmed desorption (TPD) analysis of carbon materials for revealing their carbon edge sites. Accordingly, the H 2 desorption profiles of several carbon materials, such as activated carbon, carbon black, reduced graphene oxide (rGO), phenol resin carbon, graphite, high-temperature treated carbon, and carbon nanotubes (CNTs), were investigated. The kinetic analysis of the profiles revealed that H 2 desorption is a second-order reaction initiated by the association of edge hydrogen. Furthermore, the relationship between the total number of edge hydrogens in a sample and the peak temperature of H 2 desorption represents the spatial distribution of edge hydrogens in the carbon structure. Additionally, most of the activated carbons, carbon blacks, and rGOs exhibited a uniform distribution of edge hydrogen throughout their carbon structures. In contrast, the edge hydrogen in graphite, high-temperature treated carbon, and CNTs were heterogeneously distributed throughout their structures. [Display omitted] [ABSTRACT FROM AUTHOR]

Onion-like carbon (OLC) is known to form as an intermediate structure when nanodiamond (ND) is heat treated at 1100–1500 °C. In this letter, we report on the electrochemical activity of its oxygen reduction reaction (ORR) when prepared at temperatures from 1000 to 2000 °C. The ORR activity is found to exhibit excellent correlation with the degree of defects, with OLC prepared at 1400 °C found to have the highest activity. This is attributed to the formation of curved graphitic layers containing edges during ND-OLC transformation, which function as active sites for the adsorption and subsequent reduction of oxygen. [ABSTRACT FROM AUTHOR]

Trace amounts of edge sites in natural graphite, synthetic graphite and high-temperature treated coke are quantitatively analyzed from the numbers of hydrogen atoms and oxygen-containing functional groups at carbon edge sites. For the analysis of hydrogen content, a new analytical technique is developed. The oxygen-containing functional groups are analyzed with a highly sensitive temperature-programmed desorption (TPD) technique. These techniques allow us to estimate the trace amounts of edge sites in the range of 1–10 × 10 −4 at.% with extremely high accuracy and reveal that the concentration and the type of edges sites differ depending on the type and the particle size of these graphitized carbons. Moreover, the average sizes of graphene sheets in these carbons are estimated from the total number of edge sites. The graphene sheet size thus obtained is compared with the crystallite sizes, L a , and the average particle size, and such comparison provides deep insight into the understanding of carbon molecular structure in the graphitized carbons. [ABSTRACT FROM AUTHOR]

Hard carbons emerge as one of the most promising candidate for an anode of Na-ion batteries. This research focuses on the carbon monolith derived from resorcinol-formaldehyde (RF) gels as a model hard carbon electrode. A series of binder-free monolithic carbon electrodes heat-treated at varied temperatures allow the comparative investigation of the correlation between carbon nanotexture and electrochemical Na + -ion storage. The increase in carbonization temperature exerts a favorable influence on electrode performance, especially in the range between 1600 °C and 2500 °C. The comparison between Li + - and Na + -storage behaviors in the carbon electrodes discloses that the Na + -trapping in nanovoids is negligible when the carbonization temperature is higher than 1600 °C. On the other hand, the high-temperature sintering at 2500–3000 °C enlarges the resistance for Na + -insertion into interlayer spacing as well as Na + -filling into nanovoids. In addition, the study on the effect of pore size clearly demonstrates that not the BET surface area but the surface area related to meso- and macropores is a predominant factor for the initial irreversible capacity. The outcomes of this work are expected to become a benchmark for other hard carbon electrodes prepared from various precursors. [ABSTRACT FROM AUTHOR]

By using non-graphitizable and graphitizable carbons prepared from poly(furfulyl alcohol) and poly(vinyl chloride), respectively, an attempt is made to determine the number of carbon edge sites by analyzing their hydrogen content and the amounts of surface oxygen complexes and localized spins. It is found that, at the present preparation conditions, the number of hydrogen-terminated edges is much higher than the number of surface oxygen complexes regardless of the type of carbon and the heat-treatment temperature, but the contribution of the localized spins derived from σ free radicals in closed spaces and/or triplet carbene/carbyne species may become comparable to the hydrogen content when the heat-treatment temperature is higher. Moreover, the average sizes of graphene layers in these carbons are estimated from the total number of edge sites. This analysis suggests that the actual size in the poly(furfulyl alcohol)-derived carbons is much larger than the size detected with transmission electron microscopy. This large difference is discussed in relation to a real structure of graphene layers in non-graphitizable carbons. [ABSTRACT FROM AUTHOR]