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Photocatalytic hydrogen production using mesoporous TiO2 doped with Pt

ABSTRACT

A series of mesoporous TiO2 (meso-TiO2) were synthesized using the sol-gel technique. A Pluronic F127 triblock-copolymer, a structure-directing agent, was incorporated as a soft template into the sol-gel. In addition, and during a separate synthesis, the sol-gel was doped with a Pt precursor. Semiconductors were prepared with 1.00 wt. %, 2.50 wt. %, 5.00 wt. % Pt nominal loadings, respectively. They were calcined at 500 °C and 550 °C following synthesis. Morphological and structural properties were studied by: a) X-ray diffraction, b) UV-Vis spectrophotometry, c) N2 adsorption-desorption (BET, BJH), and d) X-ray photoelectron spectroscopy (XPS). Optical band gap values for meso-TiO2 and Pt-meso-TiO2 were calculated by Kubelka-Munk (K-M) function coupled with Tauc plot methodology. It was observed that the prepared semiconductors displayed pore sizes in the 10 to 40 nm range with bimodal distributions. Their photocatalytic activity for hydrogen production via water splitting was established in a Photo-CREC Water-II reactor under near-UV light irradiation. The aqueous solution contained 2% v/v ethanol, employed as a renewable organic scavenger. The prepared semiconductors showed that the mesoporous 2.50 wt. % Pt-TiO2 has the highest photoactivity for hydrogen generation. This suggests the important role played by the loading of platinum as a TiO2 dopant, reducing the optical band gap, increasing electron storage and diminishing, as a result, electron-hole recombination. The measured Quantum Yield (QY), obtained using a rigorous approach, was established for the mesoporous 2.50 wt. % Pt-TiO2 at a promising level of 22.6%.

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