Formic acid produced from waste plastic — Balancing circular chemical manufacturing with energy-saving hydrogen production

A research group, including Professor Akitaka Ito, Professor Takeshi Fujita, and Assistant Professor Saikat Bolar at the School of Engineering Science, Kochi University of Technology, along with Professor Masahiro Miyauchi, Associate Professor Akira Yamaguchi, and Graduate Student Meiyi Wang at the School of Materials and Chemical Technology at the Institute of Science Tokyo, has announced the development of a new catalyst created by introducing sulfur into high-entropy oxides (HEO). The team successfully produced "formic acid" from substances derived from plastic (PET) and achieved hydrogen production with reduced energy consumption during the process.

This is expected to be applied to next-generation electrolysis processes, as it will enable recycling-oriented chemical production and low-energy hydrogen generation at the same time. The results were published in ChemSusChem on March 3.

The research group synthesized multi-element acid sulfides by introducing sulfur in a single step at room temperature to HEO, whose basic elements are manganese, iron, cobalt, nickel, and copper. The synthesized HEOS was confirmed to be homogeneously mixed by scanning electron microscope images and elemental mapping.

The covalent metal-sulfur interactions of the sulfur stabilized oxygen vacancies and maintained the transition metals in a high-valence state. This created a favorable electronic state that promotes the C-C bond cleavage of ethylene glycol (EG). The electrochemical oxidation reaction of EG showed a Faraday efficiency of up to 84.6% and achieved high selective formic acid production.

Formic acid (formate) is an oxide of one carbon obtained as the main product of EG oxidation, which is obtained in the hydrolysis of PET, and is highly useful in organic synthesis. Furthermore, in a two-electrode system experiment using PET-derived EG obtained from the alkaline hydrolysis of waste PET, the HEOS selectively produced formic acid.

By using this process as an alternative to the oxygen evolution reaction typically found in water electrolysis, the team confirmed that the cell voltage could be reduced, allowing for hydrogen production with lower energy consumption. The actual operating durability also retained approximately 92% of its initial activity after 20 hours of operation at 1.5 V in an H-type cell.

Fujita stated: "These results lead to the simultaneous resolution of energy issues and the upcycling of waste plastics into high-value-added products. We will continue to study the improvement of durability and scale-up, with the aim of commercializing this technology. Multi-element catalysts have diverse possibilities, and we will continue to take on the challenge of unexplored materials."

Journal Information
Publication: ChemSusChem
Title: Sulfur-Stabilized High Entropy Oxysulfides Enable Efficient C—C Bond Cleavage in Ethylene Glycol Electrooxidation for Sustainable Plastic Upcycling to Formate
DOI: 10.1002/cssc.202502529