CAREER: Single-Atom Alloy Nanocrystals for Catalyzing Sustainable Nitrogen Cycling

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

The industrial production of fertilizer – produced from ammonia (NH3) generated by the energy-intensive, fossil fuel-dependent Haber-Bosch (H-B) process - has disrupted the natural nitrogen cycle, resulting in groundwater pollution from nitrates (NO3-). The project utilizes electrochemistry to react nitrate compounds with hydrogen (derived sustainably from water) to manufacture NH3, while simultaneously decomposing the nitrate pollutants and restoring balance to the nitrogen cycle. Specifically, the research focuses on the discovery and design of catalysts that enable efficient nitrate-to-ammonia transformation driven by renewable electricity. Beyond the technical aspects, the project will train students from diverse groups at the interface of catalysis, chemistry, and engineering. The research will be integrated with educational and outreach efforts to illustrate the importance of sustainability in daily life while stimulating excitement for STEM amongst K-12 youth, especially those from low-income families. The electrochemical nitrate reduction reaction (NO3RR) offers a potentially attractive distributed NH3 production route, because it utilizes nitrate pollutants as the N-source, thus circumventing activation of the strong N≡N triple bond associated with the H-B process. The project will develop design strategies for single-atom alloy (SAA) electrocatalysts for the NO3RR and advance the fundamental understanding of both the catalytic active sites and the elementary mechanisms. The project is built on the central hypothesis that surface doping of Cu nanocrystals with isolated metal atoms (for example, Pt, Pd, Rh, or Ru) creates well-defined sites that activate water molecules and generate H-atoms that spill over to the Cu. The H-atoms hydrogenate N-species at low overpotentials and selectively tailoring of the binding strength of NO3RR surface intermediates through narrowly distributed d-states of single atoms for high-rate production of NH3, can potentially go beyond adsorption-energy scaling limitations. Catalyst synthesis, characterization, and electrochemical evaluation will be facilitated by advanced characterization techniques including operando surface-enhanced infrared absorption spectroscopy, differential electrochemical mass spectrometry, in-situ X-ray absorption spectroscopy, advanced electron microscopy, and computational tools such as density functional theory. The educational components of the project include (1) integrating research into the curriculum, (2) interdisciplinary student training, (3) involving diverse underrepresented students in science and engineering, and (4) implementing STEM-based outreach programs through the Center for Enhancement of Engineering Diversity at Virginia Tech and summer programs at Wonder Universe: A Children’s Museum. In addition, the newly launched Virginia Clean Energy and Catalysis Club will be leveraged as a platform to promote student training. The outreach plan also includes the development of an interactive play-based pedagogical platform, “Sustainable City in Minecraft,” that will provide young students the opportunity to design and construct a futuristic sustainable city. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.