A green method to prepare magnetically recyclable Bi/Bi25FeO40-C nanocomposites for photocatalytic hydrogen generation

A green method to prepare magnetically recyclable Bi/Bi25FeO40-C for photocatalytic hydrogen generation and 4-nitrophenol reduction. [Display omitted] •Alg plays an important role in successful preparation of Bi/Bi25FeO40-C.•Bi and C can suppress electron-hole recombination and promote light absorption.•This synergy effect enhance photocatalytic activity of Bi/Bi25FeO40-C in H2 generation.•Its catalytic activity in p-nitrophenol reduction is even higher than some noble metallic nanoparticles. In the present work, magnetically recyclable Bi/Bi25FeO40-C nanocomposites were synthesized through a one-step hydrothermal approach and then analyzed. The analysis results manifested that non-toxic and biodegradable sodium alginate takes a key role in successful preparation of Bi/Bi25FeO40-C. Sodium alginate can totally suppresses the formation of BiFeO3 because it changes the alkalinity of the medium, and at the same time Fe precursor greatly restrains the reduction of Bi3+ to Bi by sodium alginate, so the final product is Bi/Bi25FeO40 with a small amount of Bi instead of Bi, BiFeO3 or Bi/BiFeO3. Bi/Bi25FeO40-C showed enhanced photocatalytic activity in hydrogen generation as compared with pure Bi25FeO40 due to the surface plasmonic resonance effect of Bi and electron conductivity of carbon, which promote electron-hole separation and light absorption of the Bi/Bi25FeO40-C, resulting in high photocatalytic efficiency. The Bi/Bi25FeO40-C even exhibited higher catalytic efficiency than noble metallic nanoparticles and good reusability in p-nitrophenol reduction. This work provides a green way to prepare Bi/Bi25FeO40-C for catalytic reactions.