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

• Fabrication of 1D/2D g-CNR and trimetallic CoAlLa-LDH heterojunction for CO 2 reduction. • 1D g-CNR provides extra active reaction place and permits fast photogenerated charge carriers separation. • 2D/2D g-CNR/CoAlLa-LDH interface heterojunction showed S-scheme mechanism for efficient CO 2 reduction. • The photocatalytic bireforming of methane resulted in syngas (CO/H 2 ) evolution. • The enhanced visible light activity attributed to the formation of S-scheme with good stability. 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 CO 2 reduction with H 2 O resulting in maximum CO and CH 4 production of 17.85 and 14.66 µmole, respectively. The photocatalytic bireforming (BRM) of methane resulted in the production of syngas (CO/H 2 ) with 12.32 and 5.96 µmole of CO and H 2 , 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 CO 2 reduction and other solar energy application.