GIST Achieves World’s Highest Performance in Solar-Powered Bias-Free Upcycling

(From left) Professor Lee Sanghan, Department of Materials Science and Engineering, Kim Yejun, Integrated Master-PhD Program Student.

Gwangju Institute of Science and Technology (GIST) announced on August 4 that the research team led by Professor Lee Sanghan from the Department of Materials Science and Engineering has successfully achieved the world's highest performance in "bias-free upcycling" technology, which converts industrial waste into high-value-added chemicals using only sunlight.

The research team developed a photoelectrochemical system that combines an organic semiconductor-based photoelectrode with a nickel-iron-phosphorus (Ni-Fe-P) catalyst. Using this system, they succeeded in simultaneously converting glycerol and nitrate?major wastes generated in the biodiesel industry?into formic acid and ammonia, respectively.

Upcycling is a technology that recycles industrial waste or low-value substances into high-value-added products. Bias-free upcycling refers to a process in which all the energy required for recycling is supplied solely by renewable energy.

Biodiesel has been highlighted as the most suitable eco-friendly energy source for large-scale, long-distance transportation by land, sea, and air. However, its production process generates large amounts of low-value waste glycerol, and the increased concentration of nitrate in water and soil due to fertilizer use has been pointed out as a social problem.

Existing upcycling technologies for glycerol and nitrate require high external voltage and have difficulty selectively converting them into desired substances, which has limited their commercialization.

Schematic diagram of the zero-voltage solar upcycling used in this study.

To address these issues, the research team developed a nickel-iron-phosphorus (Ni-Fe-P) electrocatalyst capable of simultaneously processing nitrate reduction and glycerol oxidation. They also applied a metal foil encapsulation technique to the organic semiconductor-based photoelectrode, greatly enhancing its durability.

The nickel-iron-phosphorus (Ni-Fe-P) catalyst is produced by doping phosphorus (P) into a nickel-iron alloy, which adjusts the electronic structure of the metal catalyst, resulting in high corrosion resistance and reaction selectivity.

The research team combined the Ni-Fe-P catalyst, electroplated on copper foil, with an organic semiconductor photoelectrode. This enabled the construction of a bias-free photoelectrochemical system that simultaneously drives nitrate reduction at the photocathode and glycerol oxidation at the photoanode. As a result, they succeeded in upcycling two types of industrial waste simultaneously using only sunlight, without any external power supply.

This system converts glycerol into formic acid and nitrate into ammonia, allowing both wastes to be transformed into high-value-added chemicals without any power supply.

In actual reaction experiments, the system demonstrated a reaction current density of 11.04 mA/cm², and the Faradaic efficiency for both formic acid and ammonia production exceeded 95%, proving its high reaction activity and selectivity.

This research has laid a technological foundation for the eco-friendly production of various high-value-added chemicals, including not only ammonia but also formic acid, and is expected to have a broad impact across the chemical and energy industries in the future. In particular, the significant improvement in the durability of organic semiconductor photoelectrodes is highly regarded for its potential scalability to large-area, solar-powered chemical processes.

Professor Lee Sanghan stated, "This research is a decisive technological breakthrough that accelerates the commercialization of eco-friendly upcycling systems operating solely on sunlight, without external power." He evaluated, "It opens new possibilities for developing sustainable processes that convert industrial waste into high-value-added chemicals."

This research, supervised by Professor Lee Sanghan and conducted by doctoral student Kim Yejun from the Department of Materials Science and Engineering, was supported by the Basic Research Program (Mid-career Researcher Program) of the Ministry of Science and ICT and the National Research Foundation of Korea, as well as the Future Hydrogen Original Technology Development Project. The results were published online in the international journal 'Advanced Materials' on August 1, 2025.

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