Alginate as template in the preparation of active titania photocatalysts

Abstract

[EN] A simple and reliable procedure to prepare TiO2 and Au/TiO2 samples with high photocatalytic activity for hydrogen generation from water/methanol mixtures is reported, which uses natural alginate as the templating agent. Aqueous solutions of sodium alginate are flocculated as beads by Ti=O2+ ions in the presence or absence of AuCl4 . The resulting alginate beads containing approximately 25 wt% of Ti and various Au contents are dehydrated by ethanol washings before drying under supercritical CO2 conditions. The key step in the preparation method is to obtain Au/Ti-containing alginate aerogels of approximately 700 m2g 1 Brunauer¿Emmett¿Teller surface area. The surface area of the TiO2 and Au/TiO2 samples obtained after calcination of the organic biopolymer at 4508C under air ranges from 187 to 136 m2g 1, and the Au content has been varied from 1.3 to 0.05 wt% to optimize the photocatalytic activity of the samples. TiO2 forms in the anatase phase according to XRD and Raman spectroscopy. The highest activity Au/TiO2 sample (containing 0.556 wt% of Au) prepared by means of the biopolymer templating method was approximately eight times more active for hydrogen generation using a solar simulator than was an analogous Au-containing TiO2 P25 sample prepared by means of the conventional deposition¿precipitation method.