Remarkable effect of BaO on photocatalytic H2 evolution from water splitting via TiO2 (P25) supported palladium nanoparticles

Abstract

Here we report a versatile strategy based on the use of BaO as an electron promoter to boost the photocatalytic activity of TiO2 based, Pd supported photocatalysts for hydrogen production from water splitting. Pd-BaO nanoparticles were deposited on the TiO2 surface by simple chemical reduction method using NaBH4 as reductant. The as-synthesized Pd-BaO/TiO2 photocatalysts showed a remarkably high performance in hydrogen production, approximately 29.6 mmol g−1h−1 using an ethanol-water mixture (5% ethanol and 95% water), which is two times higher than Pd/TiO2 photocatalyst, where the latter is already regarded as the most active metal based TiO2 photocatalysts for H2 production. This high hydrogen production efficiency was attributed to the inherent high catalytic activity of palladium nanoparticles and electronic promotional effect of BaO. The Ba (in the form of BaO) greatly enhanced the electron transfer from the semiconductor conduction band to Pd centers by raising the Fermi level of TiO2 during photo-irradiation. Most importantly, Pd is present exclusively in zero oxidation state, which is ideal for proton reduction in the as-prepared photocatalysts due to close proximity of highly electropositive BaO. The structural morphologies and mechanistic aspects of the Pd-BaO/TiO2 photocatalysts are addressed by using UV–Vis/DRS, XRD, TEM, and XPS characterization techniques.