The Research On The Modification And Photoelectrocatalytic Performance For Graphitic Carbon Nitride

The depletion supply of fossil energy and the serious pollution of ecological environment force human to strengthen the development of new clean energy and the government of environmental pollution.Photoelectrocatalysis has great potential in the field of sustainable energy conversion and environment governance,especially,photoelectrocatalysis driven by solar energy has attracted increasing attention.Traditional precious metal and metal-based photoelectrocatalyst possess high catalytic activity and efficiency,however,the low reserves of precious metal,the instability of metal compounds and the low response of sunlight prevent them from commercial application.Recently,graphitic carbon nitrogen（g-C₃N₄）has shown great potential in the field of photoelectrocatalysis due to its special graphite-like structure and photoelectric characteristics.However,the photoelectrocatalytic activity of g-C₃N₄still needs to be improved in practical applications.In this paper,the composition,structure and morphology of g-C₃N₄are modified by the construction of heterojunction and the dope of heteroelement.The changes of photoelectrocatalytic performance of g-C₃N₄is studied before and after modification,and the modification mechanism of g-C₃N₄is investigated.Specific overview is as follows:（1）The g-C₃N₄/g-C₃N₄metal-free homojunction with lamellar structure is synthesized through partial hydrolysis of melamine in alkali solution and subsequent thermal treatment,which features with large exposed surface area,abundant interface contact and more channels for mass transfer.The Z-scheme transfer mechanism in the homojunction promotes the efficient separation of photogenerated carriers and the production of active species.The g-C₃N₄/g-C₃N₄homojunction shows excellent performance for photoelectrocatalytic OER and HER with a small overpotential of 383.4 mV and 150.1 mV at 10 mA cm^-2,low Tafel slope of 69.52 mV dec^-1and 67.93 mV dec^-1for OER in 1.0 M KOH solution and HER in 0.5 M H₂SO₄solution,respectively.And still stable in alkali solution for 7 h.This work provides a facile but effective approach for the construction of metal-free HER/OER bifunctional catalysts with high photo-response performance,achieving higher activity for catalyst-assisted water splitting.（2）A modified g-C₃N₄with Fe doping and lamellar rod-like morphology is synthesized by the influence of Fe intervene.The appropriate amount of Fe doping directly optimized the morphology of g-C₃N₄,so that g-C₃N₄retained the original rod-like structure of the precursor,and generated lamellar structure on the surface.The formation of lamellar rod structure enhance the adsorption capacity,charge transfer and the collection of visible light of g-C₃N₄,which is beneficial to the adsorption of contaminant molecule and the generation of photogenic carriers for photocatalysis.As a result,the photocatalytic performance is greatly improved:the photocatalytic degradation efficiency of Rh B is up to 90%,and the degradation rate is 0.501 h^-1,which is about 3.4 times higher than that of bulk g-C₃N₄.This work provides a new ideal for the construction of photocatalyst with high activity and wide light response for efficient decomposition of organic pollutants.