麻豆淫院

A research team affiliated with UNIST has unveiled a technology that transforms nitrates found in wastewater into ammonia, a vital chemical and promising energy carrier, without carbon emissions. This advancement not only offers a sustainable method for ammonia production but also contributes to wastewater purification efforts.

Jointly led by Professors Kwanyong Seo and Ji-Wook Jang from the School of Energy Chemistry at UNIST, the research team successfully engineered a solar-powered photoelectrochemical (PEC) system capable of converting nitrate pollutants into ammonia under ambient conditions. The research is in the journal Advanced Materials.

Ammonia is an essential chemical used globally in agriculture and industry, with an annual consumption exceeding 150 million tons. Its high hydrogen content also positions it as a promising candidate for next-generation energy storage and transportation solutions. However, the prevailing industrial method鈥攖he Haber-Bosch process鈥攔elies heavily on high-temperature and high-pressure conditions, resulting in significant greenhouse gas emissions.

The new PEC system utilizes sunlight to drive nitrate reduction without the need for external electrical power, leveraging wastewater as a raw material. Nitrates, when present at high concentrations, pose health risks such as methemoglobinemia and gastric cancers. The new technology selectively reduces nitrates to ammonia, effectively addressing both water pollution and sustainable ammonia synthesis.

The system includes a silicon-based photocathode paired with a nickel foil catalyst. Sunlight excites the silicon, generating electrons that are then channeled via the nickel catalyst to reduce nitrates to ammonia. A key innovation lies in the formation of a thin layer of nickel hydroxide (Ni(OH)₂) on the catalyst surface during operation, which suppresses competing reactions like hydrogen evolution and enhances selectivity toward ammonia production.

This mechanism was confirmed through extensive experiments and quantum mechanical calculations. Professor Suthsu Ryu from UNIST's Department of 麻豆淫院ics, utilizing density functional theory (DFT) simulations, demonstrated that Ni(OH)₂ offers active sites that favor nitrate reduction to ammonia, lowering the energy barriers involved.

Remarkably, the system achieved a record-high ammonia production rate of 554 micrograms per square centimeter per hour without any external bias, outperforming previous technologies by more than 50%. The system maintained its performance on a larger 25 cm² scale, indicating promising potential for real-world application.

Professor Seo noted, "Converting nitrate pollutants into ammonia not only purifies water but also contributes to carbon neutrality. Our goal is to develop large-scale, practical PEC devices capable of producing ammonia outdoors, directly utilizing sunlight and wastewater as resources."