Photodegradation catalyst screening by combinatorial methodology

In this work, a combinatorial methodology was developed for photodegradation catalyst screening. A fluorescence imaging detection system was designed for high throughput analysis, 1,6-hexamethylenediamine was used as the probe molecule for catalyst testing. The photodegradation activity of catalysts was evaluated by 1,6-hexamethylenediamine consumption during the photodegradation reaction. The methodology could provide reliable results. We found that pure TiO2, ZrO2, Nb2O5, MoO3, and WO3 did not show much activity for 1,6-hexamethylenediamine photodegradation under visible light. TiO2 catalysts doped with different metal ions were tested. When TiO2 was doped with Ta2O5, Nb2O5, V2O5, MoO3, or WO3, higher activity for photodegradation was observed. The doping of La3+, Ba2+, and Br− to TiO2 did not improve the catalytic activities. When doping TiO2 with Mn2+, Cl−, Al3+, Cu2+, Fe3+, Na+, Mg2+, Li+, F−, Co2+, or K+, catalytic activity was lower than that of pure TiO2. After elaborate catalysts screening, we discovered new catalysts, such as 50-70% TiO2/0-20% WO3/20-40% VO2.5 and 20-30% TiO2/30-50% MoO3/40-60% VO2.5 as well as 30% WO3/20% ZrO2/50% NbO2.5 (synthesized from ZrCl4, NbCl5, and (NH4)5H5[H2(WO4)6]·H2O in ethanol solution or suspension) and 60-70% WO3/Nb2O5 (synthesized from WCl6 and NbCl5 in ethanol solution). We observed that the catalytic activity is sensitive to preparation methods and catalyst specific surface areas. When P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H, designated EO20PO70EO20) was used as template to synthesize mesoporous materials, the mesoporous catalysts showed higher activity than regular catalytic materials.