Iron-substituted hydroxyapatite as a potential photocatalyst for selective reduction of CO2 with H2

Aiming at developing photoactive materials on the photocatalytic reduction of CO2 with H2 under UV light, iron-doped hydroxyapatites were evaluated through online diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) coupled with quadrupole mass spectrometer (QMS). The photocatalysts with iron content ranging from 0 to 26 wt% had a specific surface in the range of 32.6–128.0 m2.g−1 and bandgap energy values between 2.08 and 4.92 eV, respectively. Mossbauer spectroscopy combined with X-ray diffraction results confirmed the iron dispersion in the hydroxyapatite structure even in the sample with the highest metal content. The production of H2O, CO, and O2 confirmed all photocatalysts were actives for CO2 reduction. However, only the ≥ 10 wt% iron content samples presented selectivity for CH4 and C2H4 on this photoreaction. These results revealed iron-modified hydroxyapatite as a selective photocatalyst to obtain hydrocarbons.