Biomolecule Assisted Construction Of G-C₃N₄ Based Photocatalytic Composite And Its Performance

The semiconductor heterojunction with high efficiency visible light catalytic activity has great application prospects in the field of environmental pollution control and new energy.g-C₃N₄and sulfide are two representative materials with visible photocatalytic activity.The heterojunction composed of them can not only broaden the light response range of semiconductor,but also inhibit the recombination of photogenerated carriers.However,how to further improve the interface combination,improve the separation efficiency of photogenerated carriers,and obtain photogenerated electrons and holes with appropriate redox ability is still a scientific and technological problem to be solved.Based on this,we use protonated g-C₃N₄as the matrix,Au and g-C₃N₄and sulfide semiconductor heterojunction with tight binding interface through utilizing the interaction of surface abundant functional groups on the surface of biomolecules with protonated g-C₃N₄and electron transport carrier.The specific research contents and results of this paper are as follows:1.The ternary composite Cu In S₂/Au/g-C₃N₄was successfully prepared by L-cysteine biomolecules assisted hydrothermal method.The theoretical calculation and experimental results show that the cysteine molecule is beneficial to improve the interface bonding between g-C₃N₄and sulfide semiconductor.The introduction of Au nanoparticles can effectively regulate the morphology and quantity of Cu In S₂.At the same time,as an electron transport carrier,Au realizes the Z-scheme charge transfer mechanism in the heterojunction.The yields of CO and CH₄produced by the ternary heterojunction in the process of photocatalytic CO₂reduction are 5.04 and 2.87 times of g-C₃N₄,respectively,and the degradation efficiency of tetracycline is 2.07 times of g-C₃N₄.This may be due to the construction of all solid-state Z-scheme structure,which not only suppresses the recombination of photocarriers,but also effectively guarantees the redox ability of photogenerated electrons and holes.2.By adjusting the content of Cu In S₂in Cu In S₂/Au/g-C₃N₄composite,the composite with the best photocatalytic activity was selected.The results show that the agglomeration of Au/Cu In S₂can be effectively inhibited by changing the content of Cu In S₂,which can disperse on the surface of g-C₃N₄more finely and evenly,thus increasing the number of heterojunctions.When the mass ratio between Cu In S₂and g-C₃N₄is 0.8:1,it shows the best performance of photocatalytic CO₂reduction.At the same time,because Cu In S₂has good near-infrared light response performance,the efficiency for tetracycline degradation over Cu In S₂/Au/g-C₃N₄composite reached45.1%in 5 hours under near-infrared light irradiation.3.A series of Cu In S₂/Au/g-C₃N₄composites were successfully prepared by using L-cysteine biomolecules assisted hydrothermal method with graphene instead of noble metal Au nanoparticles.After the introduction of graphene,the visible light absorption ability of the composite was significantly enhanced.Under the irradiation of visiblelight,the yield of CO and CH₄produced by the composite in the process of photocatalytic reduction of CO_`is 5 times and 1.93 times of that of g-C₃N₄,respectively.The degradation efficiency of p-nitrophenol reached 85%in 75 min,which was better than that of g-C₃N₄.