The rational design of photocatalyst that can effectively reduce CO2 under visible light (λ ＞ 400 nm),and simultaneously precise control of the products syngas (CO/H2) ratio is highly desirable for the Fischer-Tropsch reaction.In this work,we synthesized a series of CeO2-decorated layered double hydroxides (LDHs,Ce-x) samples for photocatalytic CO2 reduction.It was found that the selectivity and productivity of CO and H2 from photoreduction of CO2 in conjunction with Ru-complex as photosensitizer performed an obvious “volcano-like” trend,with the highest point at Ce-0.15 and the CO/H2 ratio can be widely tunable from 1/7.7 to 1/1.3.Furthermore,compared with LDH,Ce-0.15 also drove photocatalytic CO2 to syngas under 600 nm irradiation.It implied that an optimum amount of CeO2 modifying LDH promoted the photoreduction of CO2 to syngas.This report gives the way to fully utilize the rare earth elements and provides a promising route to enhance the photo-response ability and charge injection efficiency of LDH-based photocatalysts in the synthesis of syngas with a tunable ratio under visible light irradiation.