The effect of hydrophobicity of ruthenium complex dyes on photocatalytic water electrolysis

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2024-08, Vol.130 (8), Article 569
• Main Authors: Sharif, Hossain Md, Shen, Xiao-Feng, Watanabe, Motonori
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Dyes; Electrolysis; Hydrophilicity; Hydrophobicity; Interface stability; Machines; Manufacturing; Nanotechnology; Optical and Electronic Materials; Optoelectronic devices; Photoanodes; Photoelectric effect; Photoelectric emission; Photoelectricity; Physics; Physics and Astronomy; Processes; Ruthenium compounds; Surfaces and Interfaces; Thin Films; Titanium dioxide; Titanium oxides
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-024-07730-1

Bis(2,2′-bipyridine)bis(isothiocyanato)ruthenium complexes are organo-metallic dyes having broad absorption properties in the visible region that are widely used in dye-sensitized opto-electronic devices. Here, we report the photocurrent measurement and stability studies of three Ru-complexes, cis -bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II) ( N3 ), its hydrophobic analogues cis -bis(isothiocyanato)(2,2’-bipyridyl-4,4’-dicarboxylato)(4,4’-di-nonyl-2’-bipyridyl)ruthenium(II) ( Z-907 ) and hydrophilic analogues (di-tetrabutylammonium cis -bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II), ( N719 ). Z907 shows higher stability and photoelectric conversion efficiency after 2 h analysis than its hydrophilic counter-molecules, N3 and N719 . The Z907 -TiO 2 system exhibited a 1.09 mA/cm 2 photocurrent density after 2 h of analysis, with 78% of its performance retained even after an extended 48 h of analysis. The activity of N719 -TiO 2 and N3 -TiO 2 sharply decreased after 2 h of analysis, and significant desorption of the dye present on titanium oxide was also observed. This study suggests that hydrophobicity at the electrode-dye interface is a major factor supporting the stability of the dye-sensitized photoanode.