Preparation And Photocatalytic Performance Of Bioinspired Catalyst Of Zinc Oxide Based Noble Metal Heterojunction

Nowadays,the energy crisis and environmental problems are becoming more and more serious.Solar energy is a kind of inexhaustible,clean and renewable energy,which has attracted the attention all over the world.At present,the photocatalytic oxidation technology is considered as one of the most promising technologies to solve environmental pollution problems.It is of great significance to develop a new type of photocatalytic material with high visible light use efficiency for the practical application of solar energy conversion.Green plants in nature can convert solar energy to chemical energy through photosynthesis based on the special biological structure and function characteristics.We prepare a variety of bioinspired ZnO based photocatalysts with either the powdery or three-dimensional bionic structure.In addition,we test the photocatalytic and electrochemical properties.First,we prepared a rod-like photocatalyst of Au/ZnONRs with a relatively uniform size and shape in colloidal solution with the assistance of PVP.Au nanospheres(AuNSs)are uniformly distributed on the outer surface of ZnO prism.The effect of loading of AuNSs in Au/ZnONRs was adjusted to optimize the photocatalytic activity.In addition,the effect of the diameter of Au nanoparticles on the photocatalytic properties of the heterojunction of Au/ZnONRs was investigated.The Au/ZnONRs with the medium size of AuNSs shows the best photocatalytic activity.Interestingly,the Au-ZnONRs with 40-nm AuNSs demonstrate higher photocatalytic activity than the nanohybrids with AuNSs of either smaller or larger sizes.A possible ‘‘trade-off” mechanism between efficient charge transfer for smaller NSs and stronger LSPR effect for larger ones is proposed.Second,we synthesized the photocatalyst of AuNR/ZnONDKs through in situ growth of ZnO in the colloid solution of AuNR for the first time.In the heterojunction of AuNR/ZnONDK,the AuNRs are uniformly modified on the surface of the round ZnO disk.Furthermore,the aspect ratios of AuNRs in nanohybrids of AuNR/ZnONDKs have also been tuned to achieve tunable and broad LSPR bands for obtaining an optimized photocatalytic performance.In this scenario,the AuNR-707/ZnONDKs exhibit superior photocurrent generation property due to enhanced charge transfer and quantum efficiency induced by AuNRs working as electron sink and superior solar energy absorption among the three AuNR/ZnONDKs.Recently,assembling inorganic NPs into sponge-like 3D architectures has become an important nature-inspired strategy in nano-research,which can bridge the gap between individual NPs and the collective structures intended for practical applications.Based on the structure-bionic idea,we have synthesized Au/ZnO/rGO sponge and PANI@rGO sponge nanocomposites with 3D macroporous structure through template method.They show superior electrochemical performance to planar structures,which not only has good photocatalytic degradation property of organic pollutants,but also has good hydrogen evolution activity.In addition,the effects of UV and visible light on the photocatalytic performance of Au/ZnO/CPS were investigated using different irradiation light range.We found that with the existence of both ultraviolet and visible light,a two-way traffic of electrons exists,leading to more active sites for radical production and hence higher photocatalytic efficiency.Lastly,we synthesized a bioinspired spinach leaf like Au/ZnO(s-Au/ZnO)by the method of sacrificing biological template.s-Au/ZnO not only well maintained the multi-level complex structure of spinach leaves,but also showed excellent photocatalytic property of degradation of organic pollutants and good photoelectric conversion properties.In detail,the photocatalyst of s-Au/ZnO demonstrates superior properties compared with other bionic photocatalysts reported in this paper,which holds great potential for the application in both environmental purification and solar-to-hydrogen energy conversion.