Our dependence on fossil fuels has brought air pollution to the highest level in history and caused some environmental and health problems. Among the main pollutants, the accumulation of nitrogen oxides (NOx) can cause severe respiratory diseases and imbalances in the earth's nitrogen cycle. Therefore, reducing the accumulation of nitrogen oxides is an extremely important issue.
Recently, the conversion of nitrogen oxides into harmless and even useful nitrogen products has become a promising strategy. Particularly attractive to scientists is the reduction of NOx to hydroxylamine (NH2OH), which can be used as a renewable energy source.
A new iron catalyst can help to preferentially reduce nitric oxide to hydroxylamine, opening the door to pollution control and clean energy.
The "success or failure" step that determines the production of hydroxylamine is the catalytic electrochemical reduction of nitric oxide (NO), which can generate hydroxylamine or nitrous oxide (N2O) according to the pH value of the electrolyte and the electrode potential. Studies have shown that the production of hydroxylamine is more dominant than the production of N2O, and an acidic electrolyte with a pH of less than 0 is required. However, such an acidic environment will rapidly degrade the catalyst and limit the progress of the reaction. Professor Chang Hyuck Choi of the Gwangju Institute of Science and Technology (GIST) in South Korea said that developing a new catalyst with high activity, selectivity and stability is the next challenge. His work is the catalysis of electrochemical reactions.
In a recent study published in the journal Nature Communications, Professor Choi and his colleagues from South Korea and France studied a new iron-nitrogen-doped carbon (Fe-NC) catalyst composed of an isolated FeNxCy Partly combined with carbonaceous substrate. The catalyst was chosen for its high selectivity to the NH2OH pathway and its resistance to extreme acid conditions.
The team performed operational spectroscopy (that is, during the reaction) and electrochemical analysis of the catalyst to determine its catalytic position and the pH dependence of NH2OH production.
They determined that the active site of the catalyst is the ferrous group connected to the carbon substrate, and the rate of NH2OH generation increases with the decrease of the pH value. The team attributed this characteristic to the uncertain oxidation state of NO. Finally, they achieved a high-efficiency (71%) NH2OH output in a typical NO-H2 fuel cell, establishing the practical value of the catalyst. In addition, they found that the catalyst exhibited long-term stability, and there was no sign of deactivation even after running for more than 50 hours!
This method not only reduces harmful air pollutants, but also provides a useful by-product that may play a role in leading the renewable energy society. In addition to the application of hydroxylamine in the nylon industry, it can also be used as an alternative hydrogen carrier. Therefore, the new catalyst will not only help reduce nitrogen oxide pollutants in the atmosphere, but will also lead us to the future of renewable energy.
This new discovery brings us one step closer to a pollution-free renewable energy society!
Source: Xianji.com
