Electrochemical Ammonia Generation
Globally, the discovery and commercialization of the Haber-Bosch process for the production of ammonia from nitrogen and hydrogen over 100 years ago revolutionized how crops are fertilized. As a result, food production, and the global population, increased exponentially, and we currently depend on the Haber-Bosch process for food production and availability today. However, the Haber-Bosch process, which operates at high temperature and pressure, is energetically inefficient, and the source of hydrogen primarily comes from methane gas steam reforming. Steam reforming of methane, or coal, results in the production of carbon dioxide, and thus, Haber-Bosch ammonia production is one of the top producers of greenhouse gases world-wide. Today, we look towards other potential processes and technologies as potentially more efficient and environmentally friendly alternatives to Haber-Bosch. One of the potential alternatives is the electrochemical reduction of nitrogen gas to ammonia through electrolysis of water, where the hydrogen atoms in a water molecule become the source of hydrogen for ammonia molecule formation. An electrochemical process for the reduction of nitrogen to ammonia would operate similar to an electrolyzer, where catalysts are used on the cathode and anode to reduce nitrogen and also enable oxygen evolution, respectively. This technology is scalable and potentially integratable with renewable energy sources (e.g., wind or solar), which would make the technology independent of fossil fuels. However, the electrochemical reduction of nitrogen to ammonia is extremely difficult due to a competing reaction, water reduction to hydrogen, that occurs within the same potential range as nitrogen reduction. Thus far, there has been little progress in the development of successful catalyst materials. Our research currently focuses on several unique approaches to the innovative design of non-precious metal catalysts to address the issue of reaction selectivity. Our research activities span from fundamental measurements of gas and water vapor adsorption to scale up and device-level testing of synthesized catalysts.
Press and Commentary on the field of electrochemical ammonia synthesis:
2019 ACS Energy Letters Energy Focus article: MacLaughlin, C., Role for Standardization in Electrocatalytic Ammonia Synthesis: A Conversation with Leo Liu, Lauren Greenlee, and Douglas MacFarlane. ACS Energy Letters 2019, 1432-1436.
2018 Science magazine news article: Service, R., Ammonia—a renewable fuel made from sun, air, and water—could power the globe without carbon.
Award Number: DE-SC0016529
Project: Peptide Control of Electrocatalyst Surface Environment and Catalyst Structure: A Design Platform to Enable Mechanistic Understanding and Synthesis of Active and Selective N2 Reduction Catalysts
Electrochemistry for Nutrient Recycling and Water Resource Sustainability
Nutrients such as ammonia, nitrate, and phosphate have traditionally been thought of as water contaminants in the water treatment arena. However, these compounds are critical nutrients that are used for fertilization in agriculture. These nutrients sustain life for plants, animals, and humans, and yet, we largely lose these nutrients within our current wastewater treatment processes and through runoff into the environment. This one-way flow of nutrients results in additional energy use, emissions release, and resource consumption as additional fertilizer is produced commercially to supplement food production. We are interested in understanding how electrochemical, and other, technologies might be used or developed to treat nutrients in water resources as recoverable rather than as contaminants that must be simply removed and discarded. We investigate electrochemically-driven precipitation, electrocatalytic conversion, and electrocoagulation chemistry in water matrices. We are interested in recovery of specific compounds, such as struvite (magnesium ammonium phosphate), that could be processed and reused as fertilizer compounds, as well as the conversion of compounds such as nitrate.
Award Number: 1739473
Events: 2018 INFEWS NSF Workshop at the University of Arkansas
For our work with the USDA and NIFA in the AFRI Water for Food Production program, we focus on the liquid wastewaters produced during animal production farming operations, particularly for dairy and hog farms. We are interested in approaches that might be amenable to on-farm water recycling and water reuse, and our goal as a team is to work on technology solutions with direct feedback from farmers such that we are working towards solutions that might be directly implementable. In addition to technology development and testing, we are also evaluating the life cycle and economics of technology implementation, as well as building a user interface and decision making tool that will enable farmers to understand what technologies are available for water recycling and how to make a decision regarding these technologies. This work spans the states of Arkansas, Missouri, and Nebraska and includes outreach and extension activities aimed at bringing knowledge and information to the general public and the farming communities that we aim to benefit.
Award Number: 2018-68011-28691
Project: Water and Nutrient Recycling: A Decision Tool and Synergistic Innovative Technology