SYNTHESIS AND CHARACTERIZATION OF PHOTOCATALYSTS FOR HYDROGEN GENERATION FROM WATER AND RENEWABLE

Abstract

In this work, we have studied hydrogen generation via photocatalytic water splitting using commercially available titania (P25) as semiconductor and various co-catalyst systems. To explore most active metal, different photocatalysts were synthesized by depositing 1 wt.% of Pt, Pd, Au, Ag, Cu and Ni at P25 surface via PVA-assisted sodium borohydride chemical reduction method. As-synthesized photocatalysts (M@P25) were characterized using UV-vis DRS, XRD, TEM, and XPS techniques. H2 evolution activities were determined on GC-TCD (Shimadzu 2014) using Hg-lamp (100W, 365nm) as light source and 5 vol% ethanol as sacrificial reagent. The photocatalytic activities of photocatalysts were found 17.92, 20.61, 13.92, 1.24, 5.0 and 0.61 mmol g−1h−1 respectively. The results revealed that Pd@P25 exhibits the highest H2 generation activity as compared to Pt, Au, Cu, Ni, and Ag deposited over P25. In order to further enhance the photocatalytic efficiency of Pd/P25 system, the effect of addition of alkaline earth metal oxide (AEMO) was studied. In this study, various photocatalysts i.e. Pd/SrO@P25, Pd/BaO@P25 and Pd/CaO@P25 were synthesized by depositing different wt.% ratio of Pd/Sr, Pd/Ba and Pd/Ca (overall 2 wt.%), respectively at P25 surface via in-situ reduction by NaBH4. The effect of different wt. ratio of Pd/AEMO on the photocatalytic activity was studied. The results revealed that Pd1.8Ba0.2/P25, Pd1.8Sr0.2/P25 and Pd1.0Ca1.0/P25 were found most active photocatalysts amongst each respective series, exhibiting activity of 29.2, 24.5 and 22.57 mmol g−1h−1, respectively. Thus, following activity trend; Pd:BaO/P25 > Pd:SrO/P25 > Pd:CaO/P25 was obtained. Finally, we have explored that activity of Ag@P25; a very low active photocatalyst can also be promoted via addition of SrO. In this series, the photocatalyst with different wt.% ratio of Ag/Sr@P25 were synthesized and the most active catalyst Ag2.0Sr0.5/P25 showed hydrogen generation value of 8.77 mmol g−1h−1. Overall, a better strategy which could add a better e−/h+ separation to acknowledge higher photo catalytic H2 generation activity has been demonstrated in this study.