Defect engineering in polymeric carbon nitride with accordion structure for efficient photocatalytic CO2 reduction and H-2 production

Herein, simultaneously adjustable N-vacancy defect containing and C-doped graphitic carbon-nitride nanosheets (g-CN-X) in accordion-like architectural structures have been synthesized through ethanol containing steam process for the first time. The band-gap energy of the g-CN-X could be precisely tuned enhancing visible light absorption up to the whole visible spectrum region. Henceforth, the optimized catalyst (g-CN-10) has demonstrated an impressive hydrogen evolution rate of 27.6 mmol h(-1) g(-1) which is 16.2 times higher than the bulk-g-CN, with an apparent quantum yield of 9.1 % at 420 nm wavelength. Furthermore, the g-CN-10 has showed CO2 photoreduction yield to CO production rate of 226.1 mu mol h(-1)g(- 1), about 28.6 times higher than bulk g-CN (7.9 mu mol h(-1) g(-1)). Both the performances are distinctly higher than all other previous reports. Theoretical calculations show that the defect sites lead to a more localized charge density distribution and promote photocatalytic active spots, which uplift the light absorption efficiency and improve the transport of charge carriers involved in the photocatalysis, demonstrating the importance of defect engineering to achieve highly efficient and multi-functional photocatalysis.