H2 production from methane decomposition by fullerene at low temperature

• Published in: International journal of hydrogen energy Vol. 45; no. 28; pp. 14347 - 14353
• Main Authors: Tokunaga, Tomoharu, Kuno, Kohei, Kawakami, Takumi, Yamamoto, Takahisa, Yoshigoe, Akitaka
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 21.05.2020
• Subjects: Carbon catalyst; Fullerene; Hydrogen; Methane; Fullerene; Methane; Hydrogen; Carbon catalyst
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2020.03.178

Carbon materials have previously been reported to work as catalysts for hydrogen (H2) production from hydrocarbons. Mechanisms of the catalytic behavior of graphite and carbon black (CB) have often been discussed in literature. Graphite and CB is constructed from mainly 6-membered rings with sp2 bonds. To understand the catalytic behavior of carbon materials for H2 production by methane (CH4) decomposition, the catalytic behavior of fullerenes with 6-membered rings and also those comprising 5- and 7-membered rings with sp2 bonds and their associated mechanisms should be investigated. In this study, the fullerene catalyst activity has been investigated using gas chromatography and the electronic states and nanoscale structures have been analyzed. H2 production started at 400 °C and the H2 production rate gradually increased with time, and the activation energy of the fullerene for H2 production by CH4 decomposition was found to be 166 kJ/mol. Moreover, in situ heating X-ray photon spectroscopy (XPS) measurements showed that the π-π∗ transition signal becomes stronger with increasing temperature above the threshold of 300 °C. The transition of the π electrons to π∗ orbitals upon heating is expected to decompose CH4 absorbed on fullerene. Moreover, transmission electron microscopy (TEM) analysis revealed that the generated carbon atoms from the CH4 decomposition were deposited onto the surfaces of the fullerenes, forming amorphous and layered concentric sphere carbon. Amorphous carbon is reported to not work as a catalyst for CH4 decomposition at around 400 °C. From XPS analysis and TEM observations of these two structures, it is anticipated that the ring structures without 6-membered rings in carbon materials with sp2 bonding contribute to this catalytic behavior for CH4 decomposition at a low temperature of 400 °C. •Fullerenes have catalytic ability for H2 production from CH4 starting from 400 °C.•In situ heating XPS analysis showed that π electrons were exited from 400 °C.•Amorphous and concentric sphere carbon appeared only after reaction with fullerene.•H2 production rate gradually became higher with time.•Ring structures without 6-membered rings of carbon can have catalytic abilities.