Constructing S-scheme heterojunction of carbon nitride nanorods (g-CNR) assisted trimetallic CoAlLa LDH nanosheets with electron and holes moderation for boosting photocatalytic CO2 reduction under solar energy

Abstract

Well-designed template free synthesis of one dimensional (1D) graphitic carbon nitride nanorods (g-CNR) coupled with two dimensional (2D) trimetallic CoAlLa-LDH to construct 1D/2D interface heterostructures with strong electrostatic interactions between positively charged 2D LDH sheets and negatively charged 1D g-CNR has been investigated. The lanthanum doped CoAlLa-LDH with unsaturated metal centers has increased reductive sites and oxygen vacancies that led to enhanced charge separation. The 1D g-CNR provides extra active reaction sites for the photocatalytic reaction and permit fast photogenerated charge carriers separation across the interface. The coupling of g-CNR and CoAlLa-LDH with excellent properties resulted in 1D/2D interface heterojunction with S-scheme mechanism for charge carrier transfer by maintaining and effectively utilizing useful charge carriers. The 1D/2D g-CNR/CoAlLa-LDH showed remarkable photocatalytic performance for CO2 reduction with H2O resulting in maximum CO and CH4 production of 17.85 and 14.66 µmole, respectively. The photocatalytic bireforming (BRM) of methane resulted in the production of syngas (CO/H2) with 12.32 and 5.96 µmole of CO and H2, respectively. The enhancement of photocatalytic activity is mainly due to the excellent interfacial contact of g-CNR with ternary metallic CoAlLa-LDH, thus resulting in better transfer and separation of photogenerated charge carriers due to the formation of S-scheme heterojunction. Additionally, the optimum g-CNR/CoAlLa-LDH nanocomposite acquired high photostability after consecutive experimental runs with no apparent variation. The spent catalyst showed no change in morphology, thus proving further good stability of the g-CNR/CoAlLa-LDH photocatalyst. The findings of this work would be beneficial to design template free heterojunction for photocatalytic CO2 reduction and other solar energy application.