https://doi.org/10.1016/j.cej.2022.135394
“A hydrothermal process, as previously reported, was used to synthesize CeO2 nanorods [33]. Typically, 1.730 g cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and 20.0 g of sodium hydroxide (NaOH) were dissolved in 10 mL and 70 mL of deionized water to get the solution A and B, respectively. The mixture obtained by adding solution A into solution B was stirred for 30 min at room temperature, and then transferred into a stainless-steel autoclave (100 mL) and maintained at 100 °C for 24 h. After cooling down to room temperature, the products were separated by centrifugation and then washed with water until the pH reached 7 and dried at 80 °C overnight to obtain CeO2 nanorods.
A wet impregnation method was used to prepare CeO2 supported catalysts. Typically, a predetermined amount of nickel nitrate hexahydrate Ni(NO3)2·6H2O, corresponding to 0.5 wt%, 1 wt% and 5 wt% of Ni was dissolved into 16 mL deionized water and then 0.8 g CeO2 nanorods were added. The mixture solution was stirred at room temperature for 8 h, before the evaporation of water at 80 °C and then dried overnight. The samples were reduced at 550 °C in 5% H2/N2 for 3 h at a heating rate of 2 °C min−1, and are identified as 0.5%Ni/CeO2, 1%Ni/CeO2 and 5%Ni/CeO2, respectively. When the heating rate increased to 10 °C min−1, the catalyst is designated 5%Ni/CeO2-10. The reduction temperature was determined by H2-TPR of the synthesized materials (isolated before reduction), as shown in Fig. S1, with nickel nitrate fully reduced below 550 °C. H2-TPR was carried out on VDSorb-91i purchased from Quzhou Vodo Instrument Co. Ltd. 100 mg of synthesized catalyst was placed into a U-shape tube and pre-treated at 100 °C for 30 min in pure N2. After cooling to 50 °C, H2-TPR was conducted under 5% H2/N2 (30 mL min−1) at a heating rate of 10 °C min−1 up to 800 °C.”