In a groundbreaking discovery, a research team from the University Alliance Ruhr, Germany, has uncovered a catalyst that has the potential to transform the way ammonia is converted into the energy carrier hydrogen and the fertilizer precursor nitrite. Traditionally, the production of hydrogen and fertilizer have been separate chemical processes, but this new approach demonstrates that the two can be combined on a laboratory scale. This innovative research, led by Ieva Cechanaviciute and Professor Wolfgang Schuhmann from Ruhr University Bochum, along with Bhawana Kumari and Professor Corina Andronescu from the University of Duisburg-Essen, was published in the journal Angewandte Chemie International Edition on June 23, 2024.
The production of hydrogen through the splitting of water into hydrogen and oxygen using electrical energy is a key process in creating a sustainable energy system. However, for this process to be truly sustainable, the energy used must come from renewable sources. This requirement presents a challenge, as countries like Germany, which aim to build an economy based on hydrogen, may need to import it from distant locations due to constraints on renewable energy sources. The transportation of hydrogen in its liquid form requires a significant amount of energy, as it can only exist as a liquid at extremely low temperatures or high pressures. This issue has led to the exploration of alternative concepts, such as converting hydrogen into ammonia, which has a higher energy density and becomes liquid at a more manageable temperature.
Ammonia has emerged as a promising carrier for energy due to its liquid state at higher temperatures compared to hydrogen. A tank filled with liquid ammonia can transport substantially more energy than liquid hydrogen, making it a more efficient option for energy transportation. However, the challenge lies in converting ammonia back into hydrogen at the point of use, which is typically achieved through the reverse Haber-Bosch reaction. In this process, ammonia is converted back into nitrogen and hydrogen, with hydrogen being the more valuable product. The team’s innovative approach involves combining the reverse Haber-Bosch reaction with a second electrolysis of water to produce nitrite instead of nitrogen, which can be further processed into fertilizer.
One of the critical elements in realizing this new method was finding a suitable catalyst that could facilitate the conversion of ammonia into nitrite. The inherent challenge in this process is the strong nitrogen-nitrogen triple bond in ammonia, which tends to convert into nitrogen rather than nitrite. The team successfully navigated this challenge by utilizing multi-metal catalysts, which enabled them to convert a high percentage of transferred electrons into nitrite. Additionally, the researchers were able to avoid the undesirable by-product of oxygen during water electrolysis, further validating the feasibility of their innovative approach.
The research conducted by the team from the University Alliance Ruhr represents a significant step forward in the field of sustainable energy production. By combining the production of hydrogen and fertilizer into a single process, this groundbreaking catalyst has the potential to revolutionize the way we approach energy conversion and storage. As we continue to strive towards a more sustainable future, innovations like these will play a crucial role in shaping the energy landscape of tomorrow.
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