Catalytic Resonance of Methane Steam Reforming by Dynamically Applied Charges

Catalyst design has traditionally focused on tuning active site properties to optimally bind reaction intermediates and balance the kinetic requirements of multiple, often sequential chemical processes, as necessitated by the Sabatier principle. It has recently been proposed that for reactions following certain potential energy landscapes the activity limit imposed by the Sabatier principle may be overcome by using programmed oscillations of surface electron density at the time scales of surface reactions (i.e., ‘catalytic resonance’). Here, we use a combination of density-functional theory (DFT) simulations and transient kinetic models (TKMs) to simulate the kinetics of steam reforming of methane (SRM) on Ru(211) surfaces under static and dynamic applied charges. DFT-calculated binding energies of SRM intermediates and transition states exhibit strong sensitivity to positive applied charges and follow scaling relationships unique from periodic trends across transition metals. Our simulations demonstrate that applying a small positive charge to Ru dramatically enhances the steady-state turnover frequency (TOF) of SRM by up to five orders of magnitude above the TOF observed over neutral Ru. Thus, statically charging Ru catalysts may be an effective strategy to lower the temperature requirements for SRM. Dynamic square wave oscillations in charge resulted in SRM catalytic resonance over a broad range of frequencies (f ~ 106 Hz – 1011 Hz), with the corresponding average TOFs exceeding the statically charged Ru surface by an additional 15%. Based on sensitivity analyses performed for the two endpoints of oscillation, we propose that dynamic TOF improvement beyond the Sabatier maximum can be expected when the system is oscillated between two kinetic regimes that are uniquely controlled by distinct elementary steps.