Credit: Yoshikazu Ito

Despite hydrogen’s increasing prominence as a future energy source, the safe and large-scale transportation of gaseous hydrogen remains challenging. Researchers are exploring ways to transport hydrogen in the form of liquid methylcyclohexane (MCH) by reacting it with toluene.

One such approach is organic hydride electrolytic synthesis. In this process, toluene is transferred from a cathode to an iridium oxide anode under highly acidic conditions. However, toluene oxidizes on the anode surface, forming a polymer coating that remarkably degrades the electrode’s performance. This situation highlights the need for more durable and cost-effective anode materials.
In response, researchers at the University of Tsukuba have developed a high-entropy alloy anode composed of nine non-precious metal elements using a conventional arc melting method. They also elucidated the mechanism underlying the catalytic poisoning by toluene, which considerably influences the anode durability in organic hydride electrolytic synthesis.
Their findings reveal that benzoic acid, an oxidized form of toluene, contributes notably to polymerization and anode degradation. Hence, preventing the oxidation of toluene to benzoic acid is crucial because the benzoic acid could be a trigger for polymerization. The study is published in the journal ChemSusChem.
When used in organic hydride electrolytic synthesis, the high-entropy alloy anode required an additional 0.37 V for initial operations compared with conventional iridium oxide anodes which immediately degrade in the presence of toluene. However, the newly developed anode demonstrated remarkable durability and a low production cost of less than 50 yen/g.
These attributes make it a promising alternative to iridium oxide anodes, potentially advancing the development of a large-scale hydrogen supply chain.

More information:
Aimi A. H. Tajuddin et al, Toluene‐Poisoning‐Resistant High‐Entropy Non‐Noble Metal Anode for Direct One‐Step Hydrogenation of Toluene to Methylcyclohexane, ChemSusChem (2024). DOI: 10.1002/cssc.202401071

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Team synthesizes a cost-effective, high-durability, non-noble metal alloy as alternative to iridium oxide anodes (2024, October 31)
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