Study On Chemical Conversion Of Inorganic-organic Hybrids Into In₂S₃ And WO₂/C Porous Catalytic Nanomaterials

Chemical transformation can synthesize a target material from another one, acting as an efficient strategy to obtain functional nanomaterials with particular structure and component. However, it remains a big challenge to prepare hierarchical porous ultrathin nanomaterials and porous transition metal oxides with high concentration of oxygen vacancies via a handy chemical transformation reaction. Meanwhile, how to effectively and facilely fabricate less-toxic photocatalytic and electrocatalytic materials, and study their structure- and component-dependent activity is a hotspot in fields of material chemistry and energy catalysis. In this thesis, we adopt the inorganic-organic hybrids as precursors, and describe their chemical transformation strategies to prepare two nano-catalysts, systematically studying their morphology, structure and components, as well as exploring their applications in photodegradation of methyl orange or electrocatalytic hydrogen evolution reaction. The main works of this thesis are summarized as follows:1. Via the organic-component depletion method of inorganic-organic InS-TETA hybrids, three dimensional (3D) hierarchical porous In2S3 microspheres stacked by ulthathin nanosheets have successfully been prepared. By the characterizations of products under different conditions, the reaction mechanism is proposed, in which TETA molecules in inorganic-organic hybrids will dissolve into the solvent during the reaction, causing the generation of pores and inducing the formation of ultrathin nanosheets, and as-prepared nanosheets will grow on precursors due to the less required supersaturation here. So that the microsphere-like morphology of inorganic-organic precursors is maintained with the generation of unique hierarchical porous ultrathin structure. Furthermore, as-prepared samples possess an enhanced performance toward the photodegradation of methyl orange.2. We propose a novel "oxygen extraction" method to synthesize less-toxic metallic WO2-carbon mesoporous nanowires with high concentration of oxygen vacancies from inorganic-organic nanowire-like WO3-EDA hybrids. This "hitting three birds with one stone" strategy endows the products with three features:1) mesoporous structure,2) in-situ formed carbon acting as rigid substrate with good electron conductivity,3) a large amount of oxygen vacancies which can make products metallic and provide much more active sites. The whole transformation mechanism is confirmed by testing the components of off-gas, in which nitrogen atoms in organic component can extract oxygen atoms in tungsten oxides of inorganic-organic hybrid precursors, and some carbon atoms will become in-situ formed carbon materials in products. This mechanism can be broadened into the preparation of MoO2-carbon from inorganic-organic MoO3-EDA hybrids. Electrocatalytic hydrogen evolution reaction (HER) tests reveal an excellent hydrogen generation activity of products, which has been experimentally and theoretically ascribed to the pores, closely-attached carbon materials and unique electron structure (metallic feature) caused by the large amount of oxygen vacancies.