A new multicomponent CDs/Ag@Mg-Al-Ce-LDH nanocatalyst for highly efficient degradation of organic water pollutants

A novel type of multicomponent and recyclable nanocatalyst CDs/Ag@Mg-Al-Ce-LDH was successfully assembled by functionalizing a magnesium-aluminum layered double hydroxide support doped with Ce (denoted as Mg-Al-Ce-LDH) with carbon dots (CDs) and silver nanoparticles (Ag NPs). The selection of CDs was governed by their ability to act as both the stabilizing and the reducing agent, allowing accomplishing an in situ reduction of Ag+ ions to Ag NPs at the surface of the Mg-Al-Ce-LDH matrix. The obtained CDs/Ag@Mg-Al-Ce-LDH nanocatalyst and the related CDs@Mg-Al-Ce-LDH and Ag@Mg-Al-Ce-LDH materials were fully characterized by standard methods. The catalytic activities of all these materials for the reduction of 4-nitrophenol (4-NP) and discoloration of common organic water pollutants were investigated in detail. Among the tested heterogeneous catalysts, the multicomponent CDs/Ag@Mg-Al-Ce-LDH nanocatalyst revealed an excellent catalytic performance. All the reactions are very quick and proceed in aqueous medium under ambient conditions. Such a high activity of CDs/Ag@Mg-Al-Ce-LDH could be explained by a significant synergic effect between CDs and Ag NPs, while the Mg-Al-Ce-LDH carrier itself acts as a co-catalyst wherein cerium ions also increase charge separation efficiency between surface electrons. In addition, the CDs/Ag@Mg-Al-Ce-LDH nanocatalyst can also be easily recovered and successfully reused in several consecutive reaction cycles. This CDs/Ag@Mg-Al-Ce-LDH nanocatalyst thus represents one of the most efficient and recyclable systems so far reported for the reduction of similar kinds of organic water pollutants.