Hydrothermal Carbon/Carbon Nanotube Composites as Electrocatalysts for the Oxygen Reduction Reaction

Abstract

The oxygen reduction reaction is an essential reaction in several energy conversion devices such as fuel cells and batteries. So far, the best performance is obtained by using platinum-based electrocatalysts, which make the devices really expensive, and thus, new and more affordable materials should be designed. Biomass-derived carbons were prepared by hydrothermal carbonization in the presence of carbon nanotubes with different oxygen surface functionalities to evaluate their effect on the final properties. Additionally, nitrogen functional groups were also introduced by ball milling the carbon composite together with melamine. The oxygen groups on the surface of the carbon nanotubes favor their dispersion into the precursor mixture and the formation of a more homogenous carbon structure with higher mechanical strength. This type of structure partially avoids the crushing of the nanotubes and the carbon spheres during the ball milling, resulting in a carbon composite with enhanced electrical conductivity. Undoped and N-doped composites were used as electrocatalysts for the oxygen reduction reaction. The onset potential increases by 20% due to the incorporation of carbon nanotubes (CNTs) and nitrogen, which increases the number of active sites and improves the chemical reactivity, while the limiting current density increases by 47% due to the higher electrical conductivity.

The role of mechanochemical treatment of carbon nanotubes in promoting glycerol etherification

“…These spheres were probably produced from glucose through hydrothermal treatment under the conditions used. 42,48 A similar effect was also obtained by Morais et al 50 Based on the textural analyses, EA and SEM results, it can be concluded that two types of mechanisms were employed in the present work to facilitate the functionalization of CNTs with sulfur. The first one was the creation of the new active graphene edges during ball-milling of CNTs, as evidenced by the breaking of large CNT aggregates (compare SEM micrographs in Fig.…”

WITHDRAWN: Mg-doped NiO Nanoparticles Decorated Multi-Walled Carbon Nanotube (MWCNT) Nanocomposite and their Biological Activities

“…Removal of lead nitrate (200 ppm) had been determined by atomic absorption spectroscopy, after incubation at room temperature with 16 g/L of Mg-doped NiO and Mg doped NiO\MWCNTs nanocomposites within 24 h. The percentage of lead nitrate was removed by using the synthesized nanoparticles as shown in Figure (7). The highest percentage of lead removal from watery phase were 62 and 43 performed in the presence of Mg-doped NiO NPs and Mg doped NiO\MWCNTs nanocomposite, respectively, with signi cant analyses of P≤ 0.001 observed in all treatments.…”

“…The MWCNTs also play an important role in preparing nanocomposites and treating water pollution [3][4][5][6]. The MWCNTs are produced from various methods including arc chemical vapor deposition (CVD) [6], hydrothermal processes [7], discharge [8], laser ablation [9], etc. To improve the performance of MWCNTs, the decorating them with metal oxides has been widely used due to good merits such as thermal stability and, high mechanical strength.…”

Enhanced electrocatalytic performance of N-doped carbon xerogels obtained through dual nitrogen doping for the oxygen reduction reaction

“…2d, among which quaternary-N and pyridinic-N are very likely to be benecial to the ORR catalytic process. [25][26][27] The contents of various N in samples according to the intensity of each peak deconvolution conducted by the tting program (Casa XPS Version 2.3.16 Pre-rel) are shown in Table 2, in which, quaternary N and pyridinic N for NCoNC sample account for 64.13% of the total N signicantly higher than those of CoNC (48.85%) and NCoC (53.67%).…”