Three-Dimensional Dual-Site Catalysts for Industrial Ammonia Synthesis at Dramatically Decreased Temperatures and Pressures

Industrial ammonia (NH3) production via the Haber-Bosch (H-B) process is a great achievement of the 20th century, but its energy-intensive character renders NH3 production costly. Despite considerable efforts, progress in developing an efficient H-B catalyst that operates under near-ambient conditions has been slow. In this study, we leverage the confinement concept to facilitate low-temperature and low-pressure NH3 synthesis by constructing three-dimensional (3D) dual-site environments. Through first-principles calculations and microkinetic modeling, we demonstrate that the 3D confined dual site on diporphyrins can surpass the limitations imposed by energy-scaling relations, resulting in a significantly increased turnover frequency (TOF) for NH3 production. Notably, the calculated TOF is 2-3 orders of magnitude higher than that of the commercial ruthenium catalyst at the same working conditions, thus enabling a much-milder H-B process, e.g., at a dramatically decreased working pressure of 10 bar at 590 K. We believe that the strategy will pave the way for the development of economically viable alternatives to current industrial processes.

Automated summary

This study demonstrates that the use of three-dimensional confined dual site environment can significantly improve the turnover frequency for NH3 production, surpassing the limitations of energy-scaling relations and enabling a milder Haber-Bosch process.