Photocatalytic CO2 reduction over Nb2O5/basic bismuth nitrate nanocomposites

In this work, CO2 was photocatalytic converted to valuable chemicals using photoactive basic bismuth nitrates (Bi6O(4+x)(OH)((4-x))NO3)((6-x))center dot nH(2)O, x = 0-2, n = 0-3) and niobium pentoxide nanocomposites (BBN/Nb2O5). Milder hydrothermal synthesis (at 120 degrees C) maintained the crystal lattice of the BBN precursor (Bi6O5(-OH)(3)(NO3)(5)center dot 3H(2)O), while the synthesis carried out at 230 degrees C led to lamellar Bi2O2(OH)(NO3). Despite of the sample treated at 230 degrees C did not present the required band edge positions to reduce CO2, all the other materials were active for CO2 photoreduction. CO (similar to 2.8 mu mol g(-1) h(-1)) was identified as the main product, followed by C2H4 (similar to 0.1 mu mol g(-1) h(-1)), with the latter being favored using the nanocomposite produced at 120 degrees C. Scavenger experiments revealed that the photocatalytic mechanism is based on a Z-scheme, where molecules are oxidized in the valence band of Nb2O5 and CO2 is reduced in the conduction band of BBN.