Photocatalytic properties of amorphous and graphitic carbon dots based on citric acid

The simplicity of synthesis of carbon dots with the required energetic and optical properties determines the interest in their use as photoabsorbers in photocatalytic hydrogen generation systems. In order to effectively use carbon dots with the desired characteristics, proper purification of carbon dots from low molecular weight reaction products, which can significantly alter the final properties of carbon dots, is critical. In this work, amorphous and graphitic carbon dots were prepared from citric acid and their purification procedure was carried out. Further, structural, optical and photocatalytic characterization of both the initial and purified carbon dots was performed. Analysis of the obtained data showed that low molecular weight reaction products contribute significantly to the ability of photocatalytic systems to generate hydrogen. The application of a proper procedure for purification of carbon dots is essential to obtain correct results in photocatalytic hydrogen generation experiments.