in
a vertical stainless steel reactor under magnetic stirring for 2 h and
then dried at 130 ◦C for 4 h. The reactor containing the dry mixture
was set into a furnace under N2 flow of 100 cm3 min−1, and heated
at the rate of 20 ◦C min−1 to the final temperature of 700 ◦C, which
was maintained for 1.5 h. After cooling