Photocatalytic CO2 reduction over Nb2O5/basic bismuth nitrate nanocomposites

Abstract

In this work, CO2 was photocatalytic converted to valuable chemicals using photoactive basic bismuth nitrates (Bi6O(4+x)(OH)(4-x)(NO3)(6-x)).nH2O, x = 0–2, n = 0–3) and niobium pentoxide nanocomposites (BBN/Nb2O5). Milder hydrothermal synthesis (at 120 °C) maintained the crystal lattice of the BBN precursor (Bi6O5(OH)3(NO3)5.3H2O), while the synthesis carried out at 230 °C led to lamellar Bi2O2(OH)(NO3). Despite of the sample treated at 230 °C did not present the required band edge positions to reduce CO2, all the other materials were active for CO2 photoreduction. CO (∼2.8 μmol g−1 h−1) was identified as the main product, followed by C2H4 (∼0.1 μmol g−1 h−1), with the latter being favored using the nanocomposite produced at 120 °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.