Construction And Properties Of Hybrid Catalysts Based On Two-dimensional Nanomaterials

With the decreasing fossil resources and worsening of environment, utilization of solar energy and transforming harmful substance into useful resource are both good solutions, meanwhile, the catalysts play an important role in the above-mentioned ways. Development and utilization of the catalyst has attracted many countries’ attention. In the last decade, the rapid development of two-dimensional materials (2D) creates an opportunity for obtaining catalysts with high activity. The 2D components greatly improve catalytic activities of the hybrid nanocatalysts owning to their unique structure. So far, the insufficient studies on synthetic techniques, structure designs and catalytic mechanism researches have greatly limited application and development of 2D nanocatalysts. The present thesis attempts to obtain high-activity hybrid catalysts based on 2D substances with simple and high-efficiency construction methods. Main works are presented as follows:Firstly, the CdS/RGO nanocomposite was successfully synthesized by a reflux condensation method in water-DMF mixed solution. DMF was used as both solvent and reducing agent. The effect of RGO content in CdS/RGO nanocomposites on the photocatalytic degradation of Rhodamine B (RhB) was investigated. RGO was replaced with GO in nanocomposite so as to investigate what a role conductivity played in photocatalytic process. The selectivity of the catalyst was studied by changing the substrate types. In the end, the mechanism of the improvement of photocatalytic activity of CdS anchored on RGO under solar irradiation was suggested and testified. The results showed that the optimum content of RGO to CdS was 5% while the photocatalytic activity of CdS/RGO nanocomposite was about 300% times higher than that of pure CdS. Conductivity of RGO in nanocomposite played an important role in photocatalytic process. A higher photocatalytic degradation rate was achieved for RhB compared to MB and MO. The mechanism of the improved photocatalytic activity of CdS/RGO nanocomposite could be attributed to the decrease probability of the recombination of photoexcited electron-hole pairs from semiconductor CdS and produce powerful reactive species (i.e. OH radical).Secondly, two-dimensional CUS/MoS2 nanocatalyst with high photocatalytic activity was successfully obtained by a simple wet chemical method and hydrothermal process. The role of NaOH was discussed during nanocomposite preparation. The absorption and catalysis properties of CuS/MoS2 nanocomposite were investigated under dark and solar radiation conditions, respectively. The visible light catalysis activity of CUS/MoS2 nanocomposite was predicted by the combination of DRS and theoretical calculation. Then, the photocatalytic mechanism of CUS/MoS2 nanocomposite was stdutied in detail based on EIS and theoretic calculation. The results showed that NaOH played a vital role in forming neat phase of CuS. CUS/MoS2 nanocomposite presented a very strong adsorption property resulted from its unique structure. Simultaneously, CuS/MoS2 nanocomposite possessed highly efficient solar light-driven photocatalytic activity. EIS demonstrated the more efficient transfer of charge carriers was obtained over CUS/MoS2 than CuS. Thus, the introduction of MoS2 in CuS could lead to its performance improvement. Eventually, Ag/RGO hydrogenation catalyst was fabricated by a simple hydrothermal method and convenient impregnation reduction process. The catalytic activity and durability of Ag/RGO catalyst were investigated via hydrogenation of 4-Nitrophenol (4-NP) and the catalytic activity of Ag/RGO nanocomposite was also detected through hydrogenation of several other kinds of dyes. Investigations presented that Ag nanoparticles with sizes from several to tens of nanometers were anchored uniformly on the RGO nanosheets and no aggregation was observed. The hydrogenation of organic substrates with Ag/RGO nanocatalyst could be fully completed within 10 min, showing high catalytic efficiency. The repeated tests indicated that the Ag/RGO nanocatalyst had excellent stability. The superior catalytic activity of Ag/RGO nanocatalyst might be caused by the following reasons. On one hand, highly concentrated Ag nanoparticles were anchored on the RGO nanosheets leading to improvement of both numerous active sites and enormous specific area. On the other hand, RGO provided abundant adsorption sites due to π-π stacking interaction between 4-NP and RGO, causing a high concentration of the substrates near to Ag nanoparticles.