Synthesis And Photocatalytic Properties Of Doped HCa₂Nb₃O₁₀

Production of H2 from H2O decomposition by using photocatalysts and solar energy is a convenient and inexpensive method to obtain H2. The key factor in this method is to obtain photocatalysts with high activity.Recently, with continuously being investigated the method of photocatalytic oxidation using semiconductors , layered niobates have been attracted extensive attention. Especially, more and more layered compounds have been used as catalysts owing to their unique structural feature and excellent photocatalyitc activities.A series of layered niobate were synthesized by conventional solid-state reactions, for example, HCa₂Nb₃O₁₀, HLaNb₂O₇, H₂FeNb₃O₁₀, HTiNbO₅, H₄Ta₂Nb₄O₁₇. And then the layered HCa₂Nb₃O₁₀ that was doped with various metal elements such as molybdenum, chromiuma and lanthanum were prepared by solid–stated reaction followed by an ion–exchange reaction; Pt was incorporated into the the interlayer of the host layer by successive soft chemical reaction processes under UV light irradiation. Then the samples obtained were characterized by TG-DSC, XRD, DRS, SEM. The results suggested that doping low concentration Mo(Cr,La)will not change its crystalline configuration,but its energy gap will alter.The photocatalytic activities of the samples were measured by the hydrogen gas production rate from 500 ml of 0.1 M methanol solution containing 1 g of dispersed catalyst under irradiation from a 100 W mercury lamp. The results indicated that Mo (Cr, La)-doped HCa₂Nb₃O₁₀ /Pt showed excellent hydrogen evolution activity and the activity was impacted by the doping concentration. When the doping concentration of Mo (Cr, La)-doped HCa₂Nb₃O₁₀/Pt was each best, the hydrogen evolution rate was 253 ml/h, 186ml/h and 169ml/h respectively; while the hydrogen evolution rate of undoped HCa₂Nb₃O₁₀ /Pt was just 116ml/h. Therefore, doping the host layer with metal elements was a effective method to enhance the photocatalytic activity of the catalysts.