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

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.