All chemicals used in the experiment were analytical reagents and were
used as received. In a typical procedure, 0.05 mol Bi(NO3)3 was dissolved by
30mL0.05 mol L−1 HNO3 to obtain transparent Bi3+ aqueous solution, to which
20mL polyethylene glycol (PEG-4000) was added as dispersant. Then 50mL
4 mol L−1 NaOH aqueous solution was quickly poured into the mixed solution
under vigorous stirring, which immediately resulted in the formation of yellowish
precipitates in the container. After kept at 90 ◦C for 2 h under stirring,
the as-produced precipitates were filtered, washed with alcohol and deionized
water for several times, and then dried at 60 ◦C in a vacuum drier to obtain the
final faint yellow Bi2O3 samples.