2025 AIChE Annual Meeting

(119d) Operando Understanding Nitrate Reduction to Ammonia on Titanium: Product Quantification & Surface Changes

Authors

Jinyu Guo, Stanford University
Ryan Hannagan, Tufts University
Adam Nielander, SLAC National Accelerator Laboratory
Michaela Burke Stevens, Stanford University
William Tarpeh, Stanford University
Thomas Jaramillo, Stanford University
Reactive nitrogen species are a key commodity and serve as fertilizers that sustain the global agricultural system, however, their use poses two significant challenges. First, most reactive nitrogen compounds are synthesized from ammonia (NH3) generated via the Haber-Bosch process. The Haber-Bosch process is energy-intensive, as it accounts for 2% of the world’s annual energy use (19.3 kWh/kg-N).1 Secondly, fields are often times overfertilized, leading to the release of reactive forms of nitrogen, such as nitrate (NO3-), to the environment. This reactive nitrogen pollution can lead to harmful algal blooms, hypoxic dead zones in open water and other harmful effects to the environment.2

Recently, our group has developed an analytical method using ion and gas chromatography (IC and GC), nuclear magnetic resonance (NMR), gas chromatography-mass spectroscopy (GC-MS) and 15N isotope labeling to track all possible NO3-R products to close the nitrogen mass balance. Thus far we have identified and quantified the aqueous and gaseous products of NO3-, NO2-, NOx, NH3, NH4+, N2O and H2. Furthermore, to understand the NO3-R mechanism on Ti, we have implemented operando electrochemical mass spectroscopy (EC-MS) to identify and quantify gaseous products at various given potentials. This technique, paired with ex-situ characterization elucidates properties of NO3-R to NH3 and product production that can inform the experimentation and molecular design of NO3-R systems.

References

  1. Erisman, J. W.; Sutton, M. A.; Klimont, Z.; Galloway, J.; Winiwarter, W. How a century of ammonia synthesis changed the world; Nature Publishing Group, 2008.
  2. Guest, J. S.; Skerlos, S. J.; Barnard, J. L.; Beck, M. B.; Daigger, G. T.; Hilger, H.; Jackson, S. J.; Karvazy, K.; Kelly, L.; Macpherson, L.; et al. A new planning and design paradigm to achieve sustainable resource recovery from wastewater. Environ Sci Technol 2009, 43 (16), 6126-6130. DOI: 10.1021/es9010515 From NLM Medline.