1. Time-dependent CO evolution over CeO₂, Ce_1-xBi_xO_2-δ and Bi₂O₃

2. TEM images of (a) CeO₂ and (b) Ce_0.6Bi_0.4O_2-δ, (c) EDX elemental mapping images of Ce_0.6Bi_0.4O_2-δ

3. High resolution XPS spectra of (a) Ce3d, (b) Bi4f, (c) O1s on the surface of Ce_0.6Bi_0.4O_2-δ and (d) Raman spectra of CeO₂ and Ce_0.6Bi_0.4O_2-δ

4. In-situ FT-IR spectra of CO₂ adsorption on the surface of (a) CeO₂ and (b) Ce_0.6Bi_0.4O_2-δ (the spectra of the samples swept by N₂ for 1 h as the background); In-situ FT-IR spectra of CO₂ photoreduction on (c) CeO₂ and (d) Ce_0.6Bi_0.4O_2-δ at different irradiation time (The spectra collected at 0 min of irradiation in humid CO₂ as background)

5. Scheme of the possible mechanism of CO₂ reduction on Ce_0.6Bi_0.4O_2-δ

S1. XRD patterns of CeO₂ and Ce_1-xBi_xO_2-δ

S2. EPR spectra of CeO₂ and Ce_1-xBi_xO_2-δ

S3. UV-Vis absorption spectra of CeO₂ and Ce_1-xBi_xO_2-δ with inset showing the plots of (αhυ)²versus photon energy

S4. (a) Mott-Schottky plots and (b) Electrochemical impedance spectroscopy (EIS) Nyquist plots (-0.4 V (vs Ag/AgCl), in dark) of CeO₂ and Ce_0.6Bi_0.4O_2-δ

S5. Transient photocurrent responses of CeO₂ and Ce_0.6Bi_0.4O_2-δ