A facile pyrolysis synthesis of Ni doped Ce2O3@CeO2/CN composites for adsorption removal of Congo red: Activation of carbon nitride structure

Sheet-like Ni doped Ce2O3@CeO2/CN composite is synthesized by tuning the introduction of nickel in a facile and low-cost pyrolysis process. Due to the activation of the shell-core Ce2O3@CeO2 structure, the nitrogen chemical state in the carbon nitrides is mainly in the form of an N-(C3) structure, inducing the production of excellent electronic conductivity and positive charges on carbon nitrides. For the pyrolytic synthesis of the composite, the amount of nickel doping is a crucial factor. Under no nickel condition, only CeO2 is synthesized and positively charged. With increasing nickel content, Ni doped CeO2/CN composite is prepared and negatively charged due to its main component of CeO2 and the change of its carbon nitride structure. Ni doped CeO2 prepared with high enough nickel content presents individual NiO particles and its negatively charged surface. The removal of these designed composites for anionic Congo red is utilized to reveal the significant influence of their surface structure. Ni doped Ce2O3@CeO2/CN composite depicts the highest removal performance. Ni doped CeO2/CN composite, despite the great change in its carbon nitride structure, still has much higher removal efficiency than pure CeO2. However, Ni doped CeO2 is found to have lower adsorption performance than pure CeO2.