Production of hydrogen from water-gas shift reaction over Ru-[BMIM]BF4/ZnO catalyst

•Ru nanoparticles in ionic liquids deposited on ZnO was studied for WGS reaction.•The shape/crystal plane of ZnO showed a great effect on the catalyst activity.•The rodlike ZnO supported catalyst showed the highest catalytic activity.•{100} planes improved the catalyst activity by lowering the activation energy.

In this study, four kinds of Ru-[BMIM]BF4/ZnO catalysts were prepared by the deposition of Ru nanoparticles in ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF4 on the different types of ZnO supports with specific shape. A strong shape/crystal plane effect of ZnO on the activity of Ru-[BMIM]BF4/ZnO catalysts was observed for the water-gas shift (WGS) reaction. The rodlike ZnO supported catalyst enriched by {100} planes showed higher WGS catalytic activity than dislike ZnO supported catalyst enriched {002} planes. Kinetic studies indicated that the activation energy of the Ru-[BMIM]BF4/ZnO-rod3 (43 kJ/mol) was much lower than that of Ru-[BMIM]BF4/ZnO-disk catalyst (60 kJ/mol). Physically experiments and control experiments indicated that the {100} planes of ZnO in the Ru-[BMIM]BF4/ZnO catalyst improved the adsorption of CO and increased the concentration of steam around the catalytic sites, and much more metallic Ru nanoparticles were present. In situ DRIFT experiments indicated that Ru-[BMIM]BF4/ZnO-disk catalyst showed a stronger adsorption ability toward CO2 than that of Ru-[BMIM]BF4/ZnO-rod catalysts, and the adsorbed CO2 might cover some active sites, lowering the catalytic activity of Ru-[BMIM]BF4/ZnO-disk catalyst, while formates were much easier formed in Ru-[BMIM]BF4/ZnO-rod catalysts, improving its catalytic activity.