Catalytic resonance of ammonia synthesis by simulated dynamic ruthenium crystal strain

Gerhard R Wittreich; Shizhong Liu; Paul J Dauenhauer; Dionisios G Vlachos

doi:10.1126/sciadv.abl6576

Catalytic resonance of ammonia synthesis by simulated dynamic ruthenium crystal strain

Sci Adv. 2022 Jan 28;8(4):eabl6576. doi: 10.1126/sciadv.abl6576. Epub 2022 Jan 26.

Authors

Gerhard R Wittreich^{1

2}, Shizhong Liu¹, Paul J Dauenhauer^{3

4}, Dionisios G Vlachos^{1

2

4}

Affiliations

¹ Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St., Newark, DE 19716, USA.
² RAPID Manufacturing Institute and Delaware Energy Institute (DEI), University of Delaware, 221 Academy Street, Newark, DE 19711, USA.
³ Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE, Minneapolis, MN 55455, USA.
⁴ Catalysis Center for Energy Innovation, University of Delaware, 221 Academy Street, Newark, DE 19711, USA.

Abstract

Ammonia affords dense storage for renewable energy as a fungible liquid fuel, provided it can be efficiently synthesized from hydrogen and nitrogen. In this work, the catalysis of ammonia synthesis was computationally explored beyond the Sabatier limit by dynamically straining a ruthenium crystal (±4%) at the resonant frequencies (10² to 10⁵⁺ Hz) of N₂ surface dissociation and hydrogenation. Density functional theory calculations at different strain conditions indicated that the energies of NH_x surface intermediates and transition states scale linearly, allowing the description of ammonia synthesis at a continuum of strain conditions. A microkinetic model including multiple sites and surface diffusion between step and Ru(0001) terrace sites of varying ratios for nanoparticles of differing size revealed that dynamic strain yields catalytic ammonia synthesis conversion and turnover frequency comparable to industrial reactors (400°C, 200 atm) but at lower temperature (320°C) and an order of magnitude lower pressure (20 atm).