AUTHOR=El Hakim Sara , Chave Tony , Nada Amr A. , Roualdes Stéphanie , Nikitenko Sergey I. 

TITLE=Tailoring Noble Metal-Free Ti@TiO2 Photocatalyst for Boosting Photothermal Hydrogen Production

JOURNAL=Frontiers in Catalysis

VOLUME=1

YEAR=2021

URL=https://www.frontiersin.org/journals/catalysis/articles/10.3389/fctls.2021.669260

DOI=10.3389/fctls.2021.669260

ISSN=2673-7841

ABSTRACT=<p>In this work, we provide new insights into the design of Ti@TiO<sub>2</sub> photocatalyst with enhanced photothermal activity in the process of glycerol reforming. Ti@TiO<sub>2</sub> nanoparticles have been obtained by sonohydrothermal treatment of titanium metal nanoparticles in pure water. Variation of sonohydrothermal temperature allows controlling nanocrystalline TiO<sub>2</sub> shell on Ti<sup>0</sup> surface. At 100 &lt; T &lt; 150°C formation of TiO<sub>2</sub> NPs occurs mostly by crystallization of Ti(IV) amorphous species and oxidation of titanium suboxide Ti<sub>3</sub>O presented at the surface of Ti<sup>0</sup> nanoparticles. At T &gt; 150°C, TiO<sub>2</sub> is also formed by oxidation of Ti<sup>0</sup> with overheated water. Kinetic study highlights the importance of TiO<sub>2</sub> nanocrystalline shell for H<sub>2</sub> generation. Electrochemical impedance spectroscopy points out more efficient electron transfer for Ti@TiO<sub>2</sub> nanoparticles in correlation with photocatalytic data. The apparent activation energy, E<sub>a</sub> = (25–31) ± 5 kJ·mol<sup>−1</sup>, assumes that photothermal effect arises from diffusion of glycerol oxidation intermediates or from water dynamics at the surface of catalyst. Under the heating, photocatalytic H<sub>2</sub> emission is observed even in pure water.</p>