Photocatalytic CO2 reduction to CO and CH4 using g-C3N4/RGO on titania nanotube arrays (TNTAs)

Abstract

Well-designed titania nanotubes (TNTs) arrays with hierarchical structure were anchored with graphitic carbon nitride (g-C3N4) and reduced graphene oxide (RGO) to construct ternary 2D/2D/1D g-C3N4-RGO-TNTs heterojunction for stimulating photocatalytic CO2 reduction. Controlled architecture of TNTs with outstanding length was obtained, providing excellent performance of electron transporting with proficient sorption process. Using optimized g-C3N4-RGO-TNTs composite, the highest CH4 and CO production of 3322.1 and 47,117.4 μmole m−2, respectively, was achieved after 4 h irradiation, which represent a significant improvement in the production of both the products compared to pristine TNTs. This enhancement is mainly attributed to interface charge transfer with their efficient separation within the ternary heterojunction due to RGO sandwich which acted as a solid electron mediator to suppress the charge recombination rate of charges in both the semiconductors with the synergistic effect of anatase/rutile phases. The ternary composite also exhibited the best quantum yield for CH4 and CO. By increasing pressure, the productivity was further increased due to the enhanced mass transfer. Furthermore, the stability analysis has shown good performance and durability of the composite in multiple cycles without any obvious decline. The newly developed structured composite with controlled growth of TNTs anchored with g–C3N4 and RGO would be a promising approach for other solar energy applications.