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6548 Forest Park Pkwy, St. Louis, MO 63112, USA

https://imse.wustl.edu/
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Dr. Stephan Lany, Senior Scientist, National Renewable Energy Laboratory

Currently, 80% of the global final energy consumption occurs in form of fuels and only 20% as electricity, but renewable energy additions come almost exclusively in the form of electricity (dominantly photovoltaics and wind). Thus, a successful energy transition will require enormous growth in renewables, sufficient to convert excess electricity into fuels, as well as the development of non-electricity based solar fuel technologies, which currently do not exist at production scale. This presentation focuses on solar thermochemical (STC) energy conversion and specifically hydrogen generation (STCH). The bottleneck of STCH lies in the narrow thermodynamic window of opportunity requiring oxide materials with specific thermochemical properties, i.e., enthalpies and entropies of reduction. Here, first-principles defect theory is the basis for both materials search and discovery and for the development of thermodynamic models to simulate the performance of existing and hypothetical materials. This presentation covers several aspects of our recent works: [1] The high defect concentrations required for STCH can cause defect interactions not captured by conventional dilute-defect models. We address this problem within a formalism for evaluating the free energy of defect interaction. [2] The conventional thermochemical analysis using the van’t Hoff method has several shortcomings. The chemical potential method is proposed as an alternative approach, enabling the evaluation of the temperature dependences of the reduction enthalpy and entropy, which carry important information about the defect mechanism. Simulating the STCH redox process with data from computational models reveals the importance of defect ionization and the limits of STCH performance in hypothetical materials. [3] To accelerate materials discovery, we developed a defect graph neural network (dGNN) machine learning method. This approach facilitates fast and broad materials screening.

[1] A. Goyal, M.D. Sanders, R.P. O’Hayre, S. Lany, PRX Energy 3, 013008 (2024). https://doi.org/10.1103/PRXEnergy.3.013008 

[2] S. Lany, JACS 146, 14114 (2024). https://doi.org/10.1021/jacs.4c02688  

[3] M.D. Witman, A. Goyal, T. Ogitsu, A.H. McDaniel, S. Lany, Nat. Comput. Sci. (2023). https://doi.org/10.1038/s43588-023-00495-2  

  • Justine Craig-Meyer
  • Robert Wexler
  • Yarielis Lopez

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