A Mesoporous Carbon-Supported and Cs-promoted Ru Catalyst with Enhanced Activity and Stability for Sustainable Ammonia Synthesis

A mesoporous carbon-supported Ru catalyst with Cs promotor and an open mesostructure (Cs-Ru/MPC) was prepared by a stepwise wet impregnation method and used for sustainable ammonia synthesis under mild reaction conditions using a wide range of space velocities (SV). The Cs-Ru/MPC catalyst showed higher activity and stability for ammonia synthesis than a reference catalyst with a microporous framework prepared by the same method (an active-carbon-supported and Cs-promoted Ru catalyst (Cs-Ru/AC)). It was found that the mesoporous carbon framework is a suitable medium for the dispersion of the Ru nanoparticles within a narrow size distribution, and it also protected the small Ru nanoparticles against sintering during ammonia synthesis. However, the sintering of Ru nanoparticles on the outer surfaces of the Cs-Ru/AC catalyst was observed, resulting in its deactivation. The results suggest that the Cs-Ru/MPC catalyst is applicable to real operating conditions, where there may be short warm-up and shut-down periods for hydrogen production via the electrolysis of water using intermittently available renewable electricity.