Cobalt enhanced (H/C-CdS)/CeO2 activity for visible light catalytic oxidation of formaldehyde at room temperature

The visible light catalytic oxidation of formaldehyde (HCHO) at room temperature is of great interest for improving the indoor air quality. Here, a cobalt (Co)-doped CdS-based catalyst ((H/C-CdS)/CeO2) with high visible light catalytic activity was successfully synthesized for HCHO removal at room temperature. Co addition enhanced the catalytic activity of (H/C-CdS)/CeO2, and the HCHO conversion rate reached 99.5 % for a 1 mg/L aqueous HCHO solution on the Co–(H/C-CdS)/CeO2 catalyst after 1 h at room temperature under visible light, which was greater than that of (H/C-CdS)/CeO2 (92.0 %). The (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 catalysts were systemically characterized, and the results showed that the interfacial phase junction between the hexagonal (H) and cubic (C) phases of the CdS nanoparticles (NPs) and the synergistic effect of the type II heterojunction between the CdS NPs and CeO2 nanosheets (NSs) promoted the separation of e-/h+. Moreover, the addition of Co species strongly promoted the separation of photogenerated carriers. The excellent photocatalytic activity was attributed to the good dispersion of CdS NPs, which broadened the light absorption range, exposed more active sites, and provided close contact, decreasing the migration distance of photogenerated electron-hole pairs. After that, the visible light catalytic oxidation mechanism of HCHO on both (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 followed the reaction pathway of HCHO to (CO2 + H2O).