Phase controlled synthesis of bifunctional TiO2 nanocrystallites via d-mannitol for dye-sensitized solar cells and heterogeneous catalysis

Abdullah M Al-Enizi; T A J Siddiqui; Shoyebmohamad F Shaikh; Mohd Ubaidullah; Ayman Yousef; Rajaram S Mane; Abu Ul Hassan Sarwar Rana

doi:10.1039/d0ra01366h

Phase controlled synthesis of bifunctional TiO₂ nanocrystallites via d-mannitol for dye-sensitized solar cells and heterogeneous catalysis

RSC Adv. 2020 Apr 14;10(25):14826-14836. doi: 10.1039/d0ra01366h. eCollection 2020 Apr 8.

Authors

Abdullah M Al-Enizi¹, T A J Siddiqui², Shoyebmohamad F Shaikh¹, Mohd Ubaidullah¹, Ayman Yousef³, Rajaram S Mane², Abu Ul Hassan Sarwar Rana⁴

Affiliations

¹ Department of Chemistry, College of Science, King Saud University Riyadh 11451 Saudi Arabia mtayyab@ksu.sa.
² Swami Ramanand Teerth Marathwada University Nanded-431606 MS India rajarammane1970@srtmun.ac.in.
³ Department of Mathematics and Physics Engineering, Faculty of Engineering at Mataria, Helwan University Cairo 11718 Egypt.
⁴ Department of Intelligent Mechatronics Engineering, Sejong University Seoul South Korea rana@sejong.ac.kr.

Abstract

The crystal architecture of TiO₂ was successfully tailored via a low-temperature (≤200 °C) hydrothermal process in the presence of d-mannitol for feasible applications in dye-sensitized solar cells (DSSCs) and heterogeneous catalysis. In the development of anatase-TiO₂ (A-TiO₂), d-mannitol does not merely acts as a complexing agent to manage the zigzag chains of octahedral TiO₆ ^2- with dominant edge sharing but also performs as a capping agent by influencing the hydrolysis process during nucleation, as confirmed by Fourier-transform infrared spectroscopy and dynamic light scattering studies. After physical measurements, the as-synthesized nanocrystallites (NCs) of A-TiO₂ were used in DSSCs, where a fascinating power conversion efficiency (PCE) of 6.0% was obtained, which showed excellent performance compared with commercial anatase-TiO₂ (CA-TiO₂: 5.7%) and rutile-TiO₂ (R-TiO₂) obtained without d-mannitol (3.7%). Moreover, a smart approach was developed via the A-TiO₂ catalyst to synthesize pharmaceutically important C-3 alkylated 4-hydroxycoumarins through different activated secondary alcohols under solvent-free, and heat/visible light conditions. In addition, the catalytic activity of the so-produced A-TiO₂ catalyst under solvent-free conditions exhibited remarkable recyclability with up to five consecutive runs with negligible reduction, which is superior to existing reports, and clearly reveals the novelty, and green, sustainable nature of the as-synthesized A-TiO₂ catalyst. A plausible reaction mechanism of both coupling partners was activated through the interaction with the A-TiO₂ catalyst to produce valuable C-3 alkylated 4-hydroxycoumarins with 95% yield and high selectivity.