Highly Dispersed Co Nanoparticles Prepared by an Improved Method for Plasma-Driven NH3 Decomposition to Produce H2

Previous studies reveal that combining non-thermal plasma with cheap metal catalysts achieved a significant synergy of enhancing performance of NH3 decomposition, and this synergy strongly depended on the properties of the catalyst used. In this study, techniques of vacuum-freeze drying and plasma calcination were employed to improve the conventional preparation method of catalyst, aiming to enhance the activity of plasma-catalytic NH3 decomposition. Compared with the activity of the catalyst prepared by a conventional method, the conversion of NH3 significantly increased by 47% when Co/fumed SiO2 was prepared by the improved method, and the energy efficiency of H2 production increased from 2.3 to 5.7 mol(kW·h)−1 as well. So far, the highest energy efficiency of H2 formation of 15.9 mol(kW·h)−1 was achieved on improved prepared Co/fumed SiO2 with 98.0% ammonia conversion at the optimal conditions. The improved preparation method enables cobalt species to be highly dispersed on fumed SiO2 support, which creates more active sites. Besides, interaction of Co with fumed SiO2 and acidity of the catalyst were strengthened according to results of H2-TPR and NH3-probe experiments, respectively. These results demonstrate that employing vacuum-freeze drying and plasma calcination during catalyst preparation is an effective approach to manipulate the properties of catalyst, and enables the catalyst to display high activity towards plasma-catalytic NH3 decomposition to produce H2.