One-step fabrication of Bi2MoO6 nanowires-g-C3N4 composites for outstanding photocatalytic performance in cyclohexane oxidation

Abstract

Selective oxidation of cyclohexane into cyclohexanone (K) and cyclohexanol (A) stands as a pivotal process in industrial chemistry. However, the challenges associated with activating the C-H bond and the vulnerability of KA oil to over-oxidation detract from the economic significance of this reaction. This study focuses on the preparation of a bismuth molybdate ultrathin nanowires-carbon nitride (Bi2MoO6-g-C3N4) heterojunction through a one-step hydrothermal approach for significantly improving the photocatalytic oxidation of cyclohexane. Bi2MoO6 ultrafine nanowires with the diameter of 6 nm were adhered tightly on the surface of g-C3N4 nanosheets with the assistance of oleyl amine. The type II heterojunction of Bi2MoO6-g-C3N4 composite facilitated a more efficient separation of charges and boosted the photocatalytic performance in the cyclohexane oxidation. The Bi2MoO6-g-C3N4 composite demonstrated outstanding photocatalytic performance with a 10.66 % conversion rate of cyclohexane, surpassing the individual efficiencies of Bi2MoO6 and g-C3N4 by 1.9 and 2.2 times, respectively. Moreover, it demonstrated an outstanding KA oil selectivity of 99.32 %, showcasing exceptional levels of both conversion and selectivity simultaneously. Through the utilization of photoelectrochemical analysis, research on band structures, experiments on radical trapping and monitoring, we have extensively investigated the mechanism of photocatalysis. The type II charge transfer in Bi2MoO6-g-C3N4 heterojunction restricted the redox capacity of electrons in the conduction band and holes in the valence band, effectively curbing over-oxidation reactions of KA oil, thus achieving remarkable KA oil selectivity. It offers a valuable insight into the creation of heterojunctions to boost the efficiency of photocatalytic oxidation of cyclohexane, showing promise for advancing the field of photocatalysis.