Team synthesizes cost-effective and durable non-precious metal alloy as an alternative to iridium oxide anodes

Despite the growing importance of hydrogen as a future energy source, transporting gaseous hydrogen safely and on a large scale 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 electrosynthesis. In this process, toluene is transferred from the cathode to the iridium oxide anode under strongly acidic conditions. However, toluene oxidizes on the anode surface and forms a polymer coating that significantly reduces electrode 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. We also elucidated the mechanism of catalyst poisoning by toluene, which greatly affects the durability of anodes in organic hydride electrosynthesis.

Their findings revealed that benzoic acid, the oxidized form of toluene, specifically contributes to polymerization and anode degradation. Therefore, it is important to prevent the oxidation of toluene to benzoic acid, as benzoic acid can trigger polymerization. The study was published in the journal ChemSusChem.

When used in the electrosynthesis of organic hydrides, the high-entropy alloy anode required an additional 0.37 V for initial operation compared to the conventional iridium oxide anode, which degrades quickly in the presence of toluene. However, the newly developed anode has excellent durability and has achieved a low manufacturing cost of less than 50 yen/g.

These properties make it a promising alternative to iridium oxide anodes and could advance the development of large-scale hydrogen supply chains.