Asian Research Thesis Index

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.

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