(678f) Programmable Catalysis for Steam Reforming of Methane on Ruthenium Catalysts

Methane (CH₄) is the second-most abundant greenhouse gas with a warming potential 25 times as great as carbon dioxide. Short-term action plans directed toward diminishing the effects of global warming should therefore include mitigation of methane emissions. Direct capture of stranded methane emitted from relatively intractable sources with irregular emission patterns like livestock for subsequent large-scale industrial processing faces severe economic challenges. On-site treatment of CH₄ via catalyzed steam reforming (SMR) in mobile, dynamically operated modular reactors can overcome the economic barriers of capturing stranded CH₄.

Recently, researchers at the Center for Programmable Energy Catalysis (CPEC) have showed that the interdependence of the binding energies of surface intermediates can be leveraged to enhance the catalyst turnover beyond the Sabatier limit by several orders of magnitude for a relatively simple model reaction. Practically, modulation of intermediate energies can be achieved using the electron condenser, a novel device that periodically changes the electron density at the catalyst surface via applied potentials in a programmable pattern. Energies of adsorbed intermediates at different surface charges (electron densities) were obtained by using density functional theory (DFT) calculations. Linear scaling relationships between the binding energies at different surface charges on ruthenium catalyst were identified. The charge-based scaling relations were validated with conventional metal-based relations in literature. Transition kinetic model was employed to simulate the resonance of reaction rate to dynamic change of binding energies of surface intermediates. We explored the theoretical potential of exceeding the Sabatier limit for SMR by modulating the binding energies as a square wave for a broad range of frequencies. The band of frequencies that corresponds to maximal rate enhancement is identified.