2.3 Synthesis of Ni NPs deposited on AC
The catalyst of Ni@AC was prepared by the wetness impregnation method. Ni(OAc)2•4H2O (0.1106 g) was first dissolved in 20 mL deionized water, and then 0.3 g of AC was added to the Ni solution. The resulting slurry was stirred for 24 h and then dried in oil bath at 80 °C. The dried slurry was subjected to a heating process in a tube furnace with an H2/N2(1:9) gas flow at a flow rate of 100 mL/min. The tube furnace was programmed as follows: raise to 120 °C at 2 °C/min and hold for 20 min; then further raise to 400 °C at 1 °C/min, cool down to room temperature.