Simple thermal decomposition of bismuth citrate to Bi/C/α-Bi2O3 with enhanced photocatalytic performance and adsorptive ability

Exploring a simple method to prepare efficient photocatalyst is a very important technique for practical application. Herein, α-Bi2O3, β-Bi2O3 and C/Bi/α-Bi2O3 were easily obtained by calcining bismuth citrate under different conditions. Especially, C/Bi/α-Bi2O3 obtained at 450 °C in nitrogen atmosphere exhibited superior photocatalytic activity for methyl orange (MO) and malachite green (MG) degradation under visible light irradiation, higher than β-Bi2O3 and α-Bi2O3 calcined in air at 350 °C and above 450 °C, respectively. The presence of non-burned carbon in N2 atmosphere benefits to complete transformation of β-Bi2O3 into α-Bi2O3 at a annealing temperature low to 300 °C, as well as partial reduction of Bi2O3 into Bi nanoparticles. More importantly, the remaining carbon and metal Bi could enhance visible light absorption of α-Bi2O3, generate hot charge carriers and boost electron migration efficiency, which thus dramatically improve photocatalytic activity of α-Bi2O3. Furthermore, these bismuth oxides exhibit exceptionally strong adsorption ability for cationic dyes like MG and methyl violet (MV) with help of trace amount of ethylene diamine tetraacetic acid disodium salt (EDTA-2Na) and the maximum adsorption capacity for MG on α-Bi2O3 reached 312 mg/g. The as-prepared C/Bi/α-Bi2O3 also possesses good stability and recyclibility in photocatalysis and adsorption.