Synthesis And Photocatalytic Performance Of Ag₂CO₃-based Semiconductor Composites

Nowadays the pollution problems has becoming increasingly globalized, and the discharge of pollutants in waste water exhibit diversity. Water pollution causes great damage to eco-systems, social development and human health. Although several commonly used photocatalytic materials including metal oxide semiconductors exhibit promising photocatalytic activity, there are still several problems need to be overcome. Therefore, it is a big challenge for researchers to develop novel visible-light-driven semiconductor photocatalysts for water purification and disinfection. This paper aims to synthesize silver carbonate based composite photocatalysts to improve the separation efficiency of photogenerated electron-hole pairs, thereby enhancing the photocatalytic activity and stability. The main research work can be summarized as follows:?1? Ag₂CO₃ particles have been fabricated with AgNO₃ and Na₂CO₃?10H₂O via a facile precipitation reaction. The morphology and size of the Ag₂CO₃ crystals can be regulated via the choice of various solvents and different ratio of water and organic solvent. The textural, morphological and optical properties were characterized by XRD, SEM, TEM, BET and UV-vis diffuse reflectance spectroscopy. Ag₂CO₃ microcrystals obtained in the DMSO and water with the ratio of 1:1 exhibit considerably higher photoactivity activity due to its larger surface area and stronger visible light absorption capability. The quenching effects of different scavengers suggest that holes were the main reactive species responsible for the pollutant degradation while ?OH radicals played the minor role.?2? Ag₂CO₃/AgX?X= Cl, Br, I? heterojunction photocatalysts were achieved using AgX and Ag₂CO₃ as precursors via ion exchange method. The influence of halide resources on structure, size and crystal phases of samples were studied, and photocatalytic activity was also studied by controlling various contents of AgBr. AgX nanoparticles were growth on the surface of Ag₂CO₃ particles by chemical bonding. Ag₂CO₃/AgX?X= Cl, Br, I? heterojunction photocatalysts exhibit higher photocatalytic activity and stability than that of pure Ag₂CO₃, and the sample of Ag₂CO₃/AgBr?20 wt%? shows the best photocatalytic activity. The results show that the formation of heterojunction interfaces and the matching energy level are beneficial to the efficiency separation of photogenerated electron-hole pairs, thereby enhancing the photocatalytic activity and stability.?3? A facile precipitation method was developed for the synthesis of g-C₃N₄/Ag₂CO₃ composite photocatalysts with g-C₃N₄ as precursors. Ag₂CO₃ particles were growth on the surface of g-C3N4 sheets and g-C3N4/Ag₂CO₃ were shown excellent photocatalytic activity compared with pure Ag₂CO₃. In particular, the sample of g-C₃N₄/Ag₂CO₃?4 wt%? exhibited the optimum photocatalytic activity, and the photodegradation rate constant k of g-C₃N₄/Ag₂CO₃?4 wt%? was 0.131 min-1, which was 2.68 times higher than that of pure Ag₂CO₃. More attractively, silver particles were generated on the surface of Ag₂CO₃ after five successive cycles. Based on the experimental results, the Z-scheme mechanism for the photodegradation over g-C₃N₄/Ag₂CO₃ composites was proposed. The results indicated that the enhanced photocatalytic activity and stability of g-C3N4/Ag₂CO₃ composites were attributed to the Z-scheme mechanism, which were beneficial to prevent the recombination of the photogenerated electron-hole pairs.