Construction of heterojunctions CeO2 interfaced Nb, Sn, Ti, Mo and Zn metal oxide catalysts for photocatalytic oxidation of α-pinene inert C-H

Abstract

• Heterojunctions CeO 2 -M (M = Zn, Ti, Sn, Mo, Nb) metal oxides catalysts are synthesized by sol–gel method. • CeO 2 -M catalysts show varying photoactivity for oxidation of α-pinene to aroma oxygenates. • CeO 2 -Mo shows the best photocatalytic performance for α-pinene conversion and selectivity to pinene oxide. • The contribution from interfaced redox, oxygen vacancies, and efficient separation of e - /h + are accountable for the enhanced photoactivity of CeO 2 -M catalysts than CeO 2 . • Pinene oxide is obtained with up to 64% selectivity at 66% α-pinene conversion within 5 h of reaction irradiation time. Construction of heterojunctions semiconductors provide an improvement in photo-optics for light absorption, photo carriers generation, and transfer for their efficient utilization in redox reactions. Herein, heterostructured CeO 2 catalysts containing Ti, Mo, Nb, Sn and Zn oxides nanostructures are synthesized and evaluated for their photoactivity in α-pinene selective oxidation using acetonitrile solvent at 25 °C reaction temperature. Both conversion and selectivity are affected by the nature of the hetero-interfaced metal oxide to CeO 2 . CeO 2 -Mo shows the best photocatalytic performance to achieve pinene oxide selectivity of 64% at 66% of pinene conversion after 5 h of light irradiation. The enhanced photoactivity of CeO 2 heterostructured catalysts compared to CeO 2 is ascribed to their red-shift light absorption edges to visible region because of the two metal oxides interactions and structure modifications, which improved the e - /h + charge carrier’s generation and separation for their efficient transfer due to suppressed recombination. Importantly, the combination of redox nature of interfaced CeO 2 heterostructured catalysts and oxygen vacancies shows to be pivotal for the photocatalytic activity enhancement in the selective oxidation of pinene inert C-H bond.