Modification Of Surface Defects And Pt Cocatalyst To Enhance The Photocatalytic Hydrogen Evolution Performance Of G-C₃N₄

The rapid development of industry is increasing the consumption of energy.Finding and developing new energy has become an urgent requirement to solve the current energy crisis.As a green and sustainable technology,photocatalytic technology can convert solar energy into hydrogen energy with high unit mass combustion value.However,there are two major problems in photocatalyst:low separation efficiency of photogenerated carriers and poor solar light response.As a new photocatalytic material,graphitic carbon nitride（g-C₃N₄）is a promising visible-light-responsive photocatalyst.However,the pure g-C₃N₄photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers,which limit the practical application of photocatalysts.In this paper,from the point of view of surface defect modification,the particle size,dispersion and coordinance of Pt are controlled by introducing defects into g-C₃N₄structure,so as to improve the efficiency of electron and hole separation of g-C₃N₄ and its photocatalytic activity.At the same time,the reason for the obvious difference of photocatalytic activity of Pt/g-C₃N₄ prepared by different methods was explored.The main contents of this paper are as follows:（1）The g-C₃N₄ nanosheet was synthesized by high temperature thermal polymerization.Pt was supported on g-C₃N₄ by liquid-phase chemical reduction.Defects were introduced into the structure of g-C₃N₄ after hydrogen nitrogen mixture atmosphere treatment.At the same time,the dispersion and particle size of Pt were regulated.The photocatalytic activity of water splitting was improved by loading different amount of Pt.It was found that with the increase of Pt loading,the photocatalytic activity showed a volcanic relationship that first increased and then decreased.When the loading amount of Pt is1.0%,the catalyst with the best catalytic performance is treated in hydrogen nitrogen atmosphere treatment after Pt loading by liquid-phase chemical reduction,and its hydrogen production activity can reach reached 2.316 mmolg^-1h^-1,which is 8.6 times higher than that of simple impregnation.The existence of g-C₃N₄ defects helps to stabilize metal atoms and limit the migration of metal atoms on the support to prevent the aggregation of Pt particles and to maintain the dispersion of metals,which is conducive to the improvement of photocatalytic activity.（2）In order to further study the structure-activity relationship between photocatalyst and metal co-catalyst,the activity differences of g-C₃N₄ prepared by different methods were systematically investigated.Among them,the best treatment is hydrogen nitrogen atmosphere treatment after Pt loading by liquid phase chemical reduction.Different treatment methods will affect the morphology and structure of g-C₃N₄ as well as the particle size,dispersion and the coordinance of Pt.The change of the morphology and structure of g-C₃N₄ can expose more active sites.Small Pt metal particle size and high Pt dispersion results in high photocatalytic activity.Adjusting the morphology and structure of the photocatalytst,the size,dispersion and coordinance of the supported metal co-catalyst is a effective way to enhance the photocatalytic activity.