Construction Of High Efficiency G-C₃N₄-based Photocatalyst With Amino Resin As The Structrure-directing Agent

At present,energy shortages and environmental pollution are becoming increasingly serious.It is imperative to seek green and sustainable method to solve these two major problems.As a simple,environmentally friendly technology,photocatalytic hydrogen production has aroused great attention.Graphitic carbon nitride（g-C₃N₄）,because of its unique electronic and energy band structure,excellent thermal and chemical stability,non-toxic and low-cost characteristics,has been widely concerned by the research community.However,g-C₃N₄ with low surface area limits absorption in the visible region,and the fast photo-induced carries recombination rate severely hampers the photocatalytic activity.Therefore,it is essential to make great efforts to modify the g-C₃N₄ based photocatalytic materials.In this paper,g-C₃N₄ as the research object,amino resin as the structure-directing agent,through the simple copolymerization method to construct two kinds of g-C₃N₄-based photocatalysts with special morphologies.On the one hand,effectively improving the composition and structure of g-C₃N₄,increase the specific surface area;on the other hand,optimizing energy band structure,expanding spectral absorption range,enhancing the electron transport performance and photoinduced separation rate,and thus greatly improving the photocatalytic activity of the materials.At the same time,the internal relationship between the preparation,composition,structure and photocatalytic performance of the catalysts is discussed in detail.The main contents are as follows:1.Inspired by "leaf mosaic" in botany,we successfully synthesized vine-like gC₃N₄（V-CN）using dicyandiamide-formaldehyde resin（DF-resin）as a structuredirecting agent.V-CN,unique "leaf mosaic" structure,effectively increases the specific surface area and the light utilization of the material.In addition,the introduction of DF-resin further optimizes the energy band structure of V-CN,extends its visible light response range,improves its crystalline and interfacial charge transport properties,and thus exhibits ultra-high photocatalytic activity and good catalytic stability.When DF-resin was added in an amount of 100 μL,the prepared material had the best hydrogen production activity,and hydrogen production rate was as high as 13.6 mmol h-1g-1,which was 38 times than that of melamine-derived pure g-C₃N₄,and the apparent quantum efficiency（AQE）at420 nm and 500 nm are 12.7% and 2.0%,respectively.It is one of the best photocatalytic g-C₃N₄ based photocatalysts reported.This study not only provided a new idea for the design of g-C₃N₄ nanostructures,but also made significant reference in simulating the fine structure of natural photosynthetic systems.2.We used melamine-formaldehyde resin（MF-resin）as a structure-directing agent,the tubular g-C₃N₄（TCN）was synthesized by a simple thermal condensation method.The unique tubular structure of TCN not only reduces the mass transfer resistance during the catalytic reaction,but also benefits multiple reflection and scattering of incident light,which enhances the catalyst’s utilization of light.In addition,the addition of MF-resin allows the introduction of N defects and oxygen-containing species in the TCN structure,reducing the energy level,enhancing visible light absorption,and improving the hydrophilicity of the TCN.All of these factors make TCN exhibit excellent photocatalytic activity and stability.when the addition amount of MF-resin is 0.1 ml,the prepared TCN exhibits the best photocatalytic activity,and its hydrogen production rate is 7.50 mmol h-1g-1,which is 6 times than that of g-C₃N₄,and the apparent quantum efficiency（AQE）at 420 nm is 19.2%.In this work,the simple and unique method may deepen our understanding of the preparation of g-C₃N₄-based photocatalysts with special morphology,and provide important insights into the design of new and efficient visible light catalysts based on polymer-modified g-C₃N₄.