Enhanced Photocatalytic Alcohol Oxidation at the Interface of RuC-Coated TiO2 Nanorod Arrays

Shuya Li; Eric Wolfgang Shuler; Debora Willinger; Hai Tien Nguyen; Saerona Kim; Hyeong Cheol Kang; Jae-Joon Lee; Weiwei Zheng; Chang Geun Yoo; Benjamin D Sherman; Gyu Leem

doi:10.1021/acsami.1c20795

Enhanced Photocatalytic Alcohol Oxidation at the Interface of RuC-Coated TiO₂ Nanorod Arrays

ACS Appl Mater Interfaces. 2022 Feb 23. doi: 10.1021/acsami.1c20795. Online ahead of print.

Authors

Affiliations

¹ Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210, United States.
² Department of Chemistry and Biochemistry, College of Science and Engineering, Texas Christian University, Fort Worth, Texas 76129, United States.
³ Department of Energy and Materials Engineering, Research Center for Photoenergy Harvesting & Conversion Technology (phct), Dongguk University, Seoul 04620, Republic of Korea.
⁴ Department of Chemistry, Syracuse University, Syracuse, New York 13244, United States.
⁵ Department of Chemical Engineering, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210, United States.
⁶ The Michael M. Szwarc Polymer Research Institute, 1 Forestry Drive, Syracuse, New York 13210, United States.

PMID: 35195406
DOI: 10.1021/acsami.1c20795

Abstract

Visible-light-driven organic oxidations carried out under mild conditions offer a sustainable approach to performing chemical transformations important to the chemical industry. This work reports an efficient photocatalytic benzyl alcohol oxidation process using one-dimensional (1D) TiO₂ nanorod (NR)-based photoanodes with surface-adsorbed ruthenium polypyridyl photocatalysts at room temperature. The photocatalyst bis(2,2'-bipyridine)(4,4'-dicarboxy-2,2'-bipyridine)Ru(II) (RuC) was covalently anchored onto TiO₂ nanorod arrays grown on fluorine-doped tin oxide (FTO) electrode surfaces (FTO|t-TiO₂|RuC, t = the thickness of TiO₂ NR). Under aerobic conditions, the photophysical and photocatalytic properties of FTO|t-TiO₂|RuC (t = 1, 2, or 3.5 μm) photoanodes were investigated in a solution containing a hydrogen atom transfer mediator (4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl, ACT) as cocatalyst. Dye-sensitized photoelectrochemical cells (DSPECs) using the FTO|t-TiO₂|RuC (t = 1, 2, or 3.5 μm) photoanodes and ACT-containing electrolyte were investigated for carrying out photocatalytic oxidation of a lignin model compound containing a benzylic alcohol functional group. The best-performing anode surface, FTO|1-TiO₂|RuC (shortest NR length), oxidized the 2° alcohol of the lignin model compound to the C_α-ketone form with a > 99% yield over a 4 h photocatalytic experiment with a Faradaic efficiency of 88%. The length of TiO₂ NR arrays (TiO₂ NRAs) on the FTO substrate influenced the photocatalytic performance with longer NRAs underperforming compared to the shorter arrays. The influence of the NR length is hypothesized to affect the homogeneity of the RuC coating and accessibility of the ACT mediator to the RuC-coated TiO₂ surface. The efficient photocatalytic alcohol oxidation with visible light at room temperature as demonstrated in this study is important to the development of sustainable approaches for lignin depolymerization and biomass conversion.

Keywords: TiO2 nanorods; alcohol dehydrogenation; dye-sensitized photoelectrosynthesis cell; lignin conversion; mild conditions; photo-oxidation.