Preparation Of G-C₃N₄-Based Photocatalytic Materials Modified By Bimetallic Phosphides And Their Properties Of Water Decomposition For Hydrogen Production Under Visible Light

With the accelerated economic development of various countries and the further depletion of world petroleum energy,the energy problem has become more and more severe.Therefore,it is urgent to explore a new and eco-friendly way of producing new energy to solve energy shortage.In recent years,the g-C₃N₄ is a cheap and readily available photocatalytic material,which possesses high thermal stability and good resistance for acid and alkali corrosion.Meanwhile,it also has been a new research hotspot in the field of photocatalytic hydrogen evolution under visible light.The g-C₃N₄ has lots of advantages,but the rapid recombination of photo-generated electron-hole pair and the low efficiency of light utilization of g-C₃N₄ lead to the reduce of photocatalytic activity,which seriously restricts the development of its application in many fields.However,there are still many modification methods used to improve the photocatalytic performance of g-C₃N₄.Among many surface modification methods,the bimetallic phosphides modified g-C₃N₄ is an effective way to improve photocatalytic activity.At present,bimetallic phosphide is seen as premium co-catalyst for its ideal conductivity,synergistic effect and structural stability of bimetallic atoms.In this chapter,g-C₃N₄ was modified by different bimetallic phosphide,and three experimental methods were successfully designed.The main contents of this chapter were as follows:?1?Firstly,bulk g-C₃N₄ was made by thermal polycondensation of urea,and then ultrathin g-C₃N₄ was obtianed by further heat treatment.CoNiP/g-C₃N₄ photocatalyst composites were successfully prepared by electrostatically driven self-assembly method and phosphating.The results of structural characterization and performance test of CoNiP/g-C₃N₄ showed that the charge separation efficiency of g-C₃N₄ was improved by CoNiP which is modified by g-C₃N₄ without changing the structure of g-C₃N₄.Thus,its photocatalytic hydrogen production performance(71.5?mol·h^-1)was greatly improved,and it is 35 times the performance of original g-C₃N₄,and CoNiP/g-C₃N₄ also had excellent stability?cycling time was 64h?.The electrochemical impedance and transient photocurrent responses test showed that the catalyst had a faster electron transfer rate,which was an effective proof to improve the photocatalytic performance of the catalyst.?2?The bulk g-C₃N₄ was synthetized by the method of thermal condensation polymerization with urea as semifinished material,and then ultrathin g-C₃N₄ was prepared at 500?.Photocatalyst was successfully prepared by electrostatically driven self-assembly and phosphating.A series of structural and photoelectrochemical characterization of this catalyst showed that the g-C₃N₄ photocatalyst which was modified by Mo-Ni₂P did not changed structure of g-C₃N₄,and the lifetime of photongenerated carriers was enhanced.The photocatalyst of Mo-Ni₂P/g-C₃N₄showed excellent photocatalytic performance.The measurement of electrochemical impedance and transient photocurrent responses indicated that Mo-Ni₂P/g-C₃N₄ had lower electron transmission resistance and higher electron utilization efficiency,which was a good proof to improve the rate of photocatalytic hydrogen evolution.?3?The bulk g-C₃N₄ was prepared by urea in the muffle furnace at 500?,then the ultrathin g-C₃N₄ was got by air stripping under 500?.Mn_0.67Co_1.33P/g-C₃N₄photocatalyst was prepared by ethanol solvothermal and phosphating.A series of structural and photoelectrochemical tests were performed on the catalyst.The results showed that the modification of g-C₃N₄ by Mn_0.67Co_1.33P did not change the structure and characteristics of g-C₃N₄.Moreover,the photocatalytic performance and stability were enhanced.The measurement of Physical and chemical indicated that Mn_0.67Co_1.33P/g-C₃N₄ had a lower interfacial transport resistance.This is an effective proof of improving the hydrogen evolution performance of the catalyst.