2.2 Synthesis of Ni@N-C SAC
A total of 1 g Ni(OAc)2•4H2O was combined with 20 g melamine and D-glucosamine hydrochloride followed with thorough mixing. The mixture was then placed in a ceramic boat and calcined with a two-stage pyrolysis procedure: The temperature was raised to 600 °C with a heating rate of 2.0 °C/min and hold for 1 h; After that, the temperature was further raised to 800 °C with the same heating rate; Finally, the sample was cooled down to room temperature. For comparison, Ni@NC was synthesized by the above method without the addition of melamine. Similarly, 1 g D-glucosamine hydrochloride was directly calcined at 800 °C for 1h, the obtained sample was co-pyrolyzed with Ni(OAc)2•4H2O and melamine using the same process as the Ni@N-C SAC and the resultant sample was named as Ni@C. The contrastive samples were synthesized in parallel by the same method as that for Ni@N-C SAC except for the chitosan/lignin instead of D-glucosamine hydrochloride.