Sonochemical synthesis of bismuth sulfide-based nanorods for hydrogen production

Bismuth-based nanostructures have been used as promising materials for catalytic hydrogen production. Herein, a sonochemical method was developed to prepare solid solutions like Bi_2-xZn_1.5xS₃ in order to strengthen the Bi₂S₃ redox ability. Thioglycolic acid (TGA) was used as a complexing agent of Bi³⁺ to slow down Bi₂S₃ precipitation, making zinc insertion into the sulfide structure easier. The results of XRD, TEM, EDS, XPS, and DRS analyses suggest the formation of nanocomposites consisting of nanorods of Bi_2-xZn_1.5xS₃ covered by ZnS nanoparticles, with bandgap widening from 1.16 eV (Bi₂S₃) to 2.37 eV (Bi_1.53Zn_0.6S₃/ZnS/Zn(OH)₂). The hydrogen generation in an ethanol aqueous solution was investigated under sonolysis, photocatalysis and simultaneous sonolysis and photocatalysis (sonophotocatalysis) in the presence of bismuth sulfide-based nanorods. The hybrid action of light and ultrasounds determined a remarkable synergistic effect on the hydrogen production of the solid solutions. The most outstanding results were found in the presence of nanocomposites containing Bi_2-xZn_1.5xS₃, which can have an origin in better charge separation after zinc incorporation.