Prediction of a low-temperature N₂ dissociation catalyst exploiting near-IR-to-visible light nanoplasmonics.

Abstract

Despite more than a century of advances in catalyst and production plant design, the Haber-Bosch process for industrial ammonia (NH₃) synthesis still requires energy-intensive high temperatures and pressures. We propose taking advantage of sunlight conversion into surface plasmon resonances in Au nanoparticles to enhance the rate of the N₂ dissociation reaction, which is the bottleneck in NH₃ production. We predict that this can be achieved through Mo doping of the Au surface based on embedded multireference correlated wave function calculations. The Au component serves as a light-harvesting antenna funneling energy onto the Mo active site, whereby excited-state channels (requiring 1.4 to 1.45 eV, near-infrared-to-visible plasmon resonances) may be accessed. This effectively lowers the energy barriers to 0.44 to 0.77 eV/N₂ (43 to 74 kJ/mol N₂) from 3.5 eV/N₂ (335 kJ/mol N₂) in the ground state. The overall process requires three successive surface excitation events, which could be facilitated by amplified resonance energy transfer due to plasmon local field enhancement.