Multiscale Simulation Guided Electric Field-Enhanced Ammonia Catalytic Cracking

Ammonia catalytic cracking offers an efficient solution for hydrogen production, storage, and distribution, making it ideal for onboard hydrogen generation in maritime propulsion systems when integrated with fuel cells. However, conventional heating methods, even with highly active ruthenium (Ru) catalysts, require high temperatures to achieve satisfactory performance, posing a challenge for industrial implementation. A promising strategy to address this limitation is the application of strong external electric fields, which can lower the temperature requirement through interactions between fields and the dipoles of polarized species during ammonia cracking. To explore such a field-dipole effect, we developed a multiscale simulation framework that integrates density functional theory (DFT) calculations with microkinetic modeling. This framework provides mechanistic insights, identifies key rate-limiting steps, and optimizes conditions for field-enhanced ammonia catalytic cracking over Ru. Our results show that at 673 K, applying a -1 V/Å negative electric field dramatically increases the turnover frequency from 0.03 s^-1 (zero field) to 1435.2 s^-1. Similarly, at a higher temperature of 823 K, the negative electric field enhances the turnover frequency by 4 orders of magnitude compared to the no field conditions. In addition, applying a -1 V/Å electric field reduces the operating temperature from 750 K (zero field) to 586 K while maintaining a given turnover frequency (e.g., 5 s^-1). Sensitivity analysis further identifies NH dehydrogenation over Ru(1013) as the rate-limiting step across various electric fields and temperatures. This multiscale model enhances the understanding of field-enhanced catalysis, offering valuable insights into the development of more efficient hydrogen production processes.