Low-Cost Catalyst Removes Ammonia and Produces Hydrogen

In an international research collaboration, Marzieh Joda, a researcher at Amirkabir University of Technology, has developed graphite-based nanostructured manganese oxide electrodes (MnOx/Graphite). The electrodes have been used in an electrochemical system designed to directly oxidize dilute ammonia solutions while simultaneously producing nitrogen and hydrogen gases.

Thanks to their favorable structure, high active surface area, and promising electrochemical performance, these electrodes have potential applications beyond energy storage technologies, particularly supercapacitors and batteries. They could also be used to treat ammonia-containing wastewater, remove ammonia pollutants, and generate hydrogen in the same process.

The research was conducted under the supervision of Narges Fallah, a faculty member at Amirkabir University of Technology, with Chin-Pao Huang from the University of Delaware, USA, serving as an advisor.

One of the key achievements was demonstrating electrochemical performance at an operating voltage of approximately 0.6 volts, significantly reducing the energy required for ammonia oxidation. Under optimized laboratory conditions, the ammonia concentration was reduced to below 1 ppm. The study also examined and confirmed the feasibility of converting ammonia into nitrogen gas while producing hydrogen.

The electrodes were fabricated using an electrodeposition method. More than 300 samples with different compositions, fabrication conditions, and heat treatments were prepared and evaluated.

Several techniques, including field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), were used to investigate the electrodes' structures and surface properties.

Their electrochemical performance was also assessed through tests such as Tafel polarization, electrochemical impedance spectroscopy (EIS), and durability and stability evaluations. These analyses helped identify the most suitable electrode configurations and optimize operating conditions to improve catalytic activity and service life.

Key innovations include the development of an integrated, durable, and low-cost electrocatalyst that does not require a binder; engineering different manganese oxide phases to improve performance and stability; increasing the electrochemical capacitance of the graphite substrate by up to 15 times; and using intelligent computational models to predict and optimize electrode performance.

Other aspects of the research include designing advanced electrodes for energy storage and investigating the mechanisms of selective ammonia oxidation. The latter involved molecular dynamics simulations, density functional theory (DFT) calculations, and machine learning techniques.

The technology could contribute to the development of energy-efficient methods for ammonia removal, hydrogen production, and more effective use of ammonia solutions in clean energy systems. It also has potential applications in reducing ammonia pollution in industrial wastewater, particularly in the petrochemical, petroleum refining, and fertilizer industries.

The findings have been developed into four scientific papers covering electrochemistry, energy storage, and environmental science. One paper has been published in the Journal of Power Sources. Three others are at different stages of publication: one is under peer review at Advanced Energy Materials, another has been submitted to Renewable and Sustainable Energy Reviews, and the fourth is being finalized for submission to the leading journal Energy & Environmental Science.

Together, these publications reflect the scientific and interdisciplinary scope of the research and its potential to contribute to internationally recognized scientific literature.

According to Amirkabir University of Technology, the next phase of the research will focus on scaling up the technology to a pilot-scale level, testing it with real industrial solutions and wastewater, extending electrode service life, and designing larger reactors.