Hematite nanostructures: An old material for a new story. Simultaneous photoelectrochemical oxidation of benzylamine and hydrogen production through Ti doping

• Published in: Nano energy 2019-07, Vol.61, p.36-46
• Main Authors: Mazzaro, Raffaello, Boscolo Bibi, Sara, Natali, Mirco, Bergamini, Giacomo, Morandi, Vittorio, Ceroni, Paola, Vomiero, Alberto
• Format: Article
• Language: English
• Subjects: Benzylamine; Experimental Physics; Experimentell fysik; Hematite; Hydrogen; Photoanode; Photoelectrochemistry
• ISSN: 2211-2855; 2211-3282
• DOI: 10.1016/j.nanoen.2019.04.013

Overall water splitting represents one of the most promising approaches toward solar energy conversion and storage, which is, however, severely challenged by the four-electron/four-proton nature of the oxygen evolution reaction (OER). One option to overcome this issue is to replace OER with a more useful reaction, for simultaneous production of both hydrogen and chemicals of interest. For the purpose, in this paper a cheap, hydrothermally prepared Ti-doped nanostructured hematite photoanode was employed for the first time as highly stable, heterogeneous catalyst for the low bias, efficient and highly selective photoinduced oxidation of benzylamine to N-benzylidenebenzylamine, and for the simultaneous production of hydrogen in a double solvent/environment cell. A preliminary estimate indicates the possibility to obtain a ∼150 μmol h−1 H2 production, with the contemporary production of stoichiometric benzylidene N-benzylamine in a 5 × 5 cm2 area electrode. This study contributes to overcome the 40-year lasting issues limiting the use of hematite in industrial photoelectrochemical sunlight conversion and storage, due to poor performance of hematite and lack of economic value of oxygen production, providing solid evidence for the use of hematite in alternative oxidation reactions of industrial importance. [Display omitted] •Photoinduced oxidation of benzylamine and simultaneous hydrogen evolution in a double solvent/environment cell.•Ti-doped nanostructured hematite photoanodes prepared by hydrothermal synthesis.•External bias as low as +0.6 V needed for complete photoelectrochemical process.•∼150 μmol h−1 H2 production rate and contemporary production of stoichiometric N-benzylidenebenzylamine in a 5 × 5 cm2 electrode.•The role of Ti doping thoroughly investigated by electrochemical impedance spectroscopy.