Controlled Synthesis And Photocatalytic Properties Of GaN/ZnO Solid Solution Hierarchical Nanostructures

Semiconductor photocatalysis,which can make use of solar energy for pollutant degradation,water splitting,carbon dioxide reduction etc,is a promising ideal green technology for solving the environment pollution and energy crisis issues.In order to effectively utilize the solar energy,a lot of efforts have been paid on development of visible-light-active photocatalysts by means of dye-sensitizing,ion-doping,semiconductor-hybridizing etc.Making solid solution using two or more semiconductors with similar crystal structure but different electronic structures has been proven to be an effective band engineering method for developing visible-light-responsive photocatalysts.Recently,GaN/ZnO solid solution has been attracting more and more attention because of its unique band structure: the conduction band?CB?bottom is mainly composed of Ga4 s and Ga4 p orbitals,while the valence band?VB?top consists of N2 p and Zn3 d orbitals,from which the p-d repulsion results in narrowing of the band gap while keeping the CB bottom unchanged.In this thesis,we used various methods including sol-gel and chemical vapor deposition etc.to synthesize hierarchical GaN/ZnO solid solution nanostructures,and studied their photocatalytic properties.We synthesized porous GaN/ZnO solid solution nanosheets by using a sol gel method.Due to the high specific surface area and gas adsorption ability,the IPA photodegradation activity of the porous GaN/ZnO solid solution nanosheets was 15 times that of the particulate solid solution.By using different sacrificial reagents ·OH,holes and O₂·-,IPA degradation was conducted and the results indicated that both the electrons and holes played an important role in the photodegradation process.A long-term course of reaction confirmed the stability of the GaN/ZnO solid solution.Moreover,loading noble metal cocatalyst on the surface of porous GaN/ZnO solid solution nanosheets was found to favor the separation/transportation of photoexcited charge carriers,thus significantly enhancing the activity of IPA degradation to CO₂ by three-electron reaction;whereas,IPA could only be degraded to acetone by one-electron reaction without cocatalyst.We also studied the synthesis and photocatalytic property of lamellar GaN/ZnO solid solution.Since the exposed surface of two-dimensional lamellar structure was mainly composed of the highly active crystal planes,the photocatalytic activity was significantly improved.The evidence was that the activity of photocatalytic IPA degradation over the lamellar structure was 9 times that of the particulate sample.In addition,GaN/ZnO solid solution nanowires were synthesized for photocatalytic CO₂ reduction.The results showed that,owing to the superior charge carrier transport property,the one-dimensional GaN/ZnO solid solution nanowires exhibited a much higher activity than the particulate solid solution sample.