Synthesis of Au-CeO2 and its catalytic activity for reduction of p-Nitrophenol / Nurul Syafiqah Fadzli

Cerium oxides (CeO2) possess remarkable optical properties, high warm solidity, good electrical conductivity, and diffusivity. They are widely used in sensors, absorbents, and catalytic materials. Specifically for catalysis, the CeO2 are used as support for gold (Au) nanocatalyst to improve the stability of the gold and prevent it from agglomeration. Various method for producing CeO2 in form of nanoparticles has been investigated including hydrothermal, sol-gel, co-precipitation and mechanochemical. However, these methods are expensive, lengthy preparation procedures and requires the use of surfactant. Therefore, this work proposed a simple and low-cost co-precipitation method that uses cerium nitrate and potassium carbonate as precursors. This work aims to optimize the preparation of CeO2 in terms of cerium nitrate pH and calcination temperature. Furthermore, the optimized CeO2 were used as support for the gold catalyst (Au-CeO2). The Au-CeO2 was prepared by deposition and precipitation (DP) method and this catalyst was tested for the reduction of p-nitrophenol (p-NP). Characterization of CeO2 by FTIR showed the optimized cerium nitrate pH at 6 and calcination temperature of 800 oC produced a pure CeO2 without impurities. Moreover, the characterization of Au-CeO2 catalyst by FTIR confirmed the immobilization of Au on CeO2 support as the shifting from 3394 to 3412 cm-1 for the O-H band and 570 to 548 cm-1 for Ce-O band occurred respectively. The catalytic activity of p-NP reduction achieved 58.22% conversion to p-aminophenol (p-AP) with the rate constant (k) of 0.0359 min-1. The successful reduction of p-nitrophenol over Au-CeO2 catalyst proved the CeO2 prepared by co-precipitation method is a good support for Au catalyst.