Solar photocatalytic H2 production over CeO2-based catalysts: Influence of chemical and structural modifications

Different CeO2-based materials employed as unconventional photocatalysts for H-2 production were here examined. The performances of bare CeO2 prepared by precipitation were compared with those of CeO2-WO3 composites synthetized by co-precipitation and surfactants-mediated precipitation. The bare CeO2 and the best CeO2-WO3 composite were treated with laser irradiation to investigate the modifications of cerium oxide due to this process. Considering the photocatalytic performance, the CeO2-WO3 composite prepared with the HMTA (hexamethylenetetramine) surfactant and irradiated with laser increased the H2 production up to 4 times compared to the bare CeO2, whereas the laser-modified CeO2 and the CeO2-WO3 synthetized by co-precipitation led to a smaller increase of H-2 evolution (1.4 and 1.2 times higher than the as-prepared CeO2, respectively). On the basis of the characterization data (Raman, UV-vis Diffuse Reflectance, Photoluminescence, X-ray photoelectron spectmscopies, Transmission electron microscopy and N-2 physisorption measurements) it was established that the addition of the HMTA gave higher WO3 dispersion, whereas the subsequent laser treatment facilitated the progressive incorporation of WO3 into CeO2, resulting in a more efficient doping process and a more defective CeO2. All these features were beneficial for the photopmduction of hydrogen. The tuning and the combination of the chemical and the structural modifications of ceria can be a promising route for the solardriven photocatalysts designed for the green production of H-2.