Solvent-dependent self-assembly of a ruthenium(II) complex bearing triazino-phenanthrenes and its applications in photocatalytic ascorbate fuel cells

Abstract

The triazine-based metal-organic frameworks (MOFs) are of great significance in a photocatalytic or electrocatalytic system. This paper reports solvent-dependent self-assembly and photoelectrochemical properties of [Ru(ptp)2]2+ (ptp = 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6,f]phenanthrene) and its photoelectrocatalysis to ascorbate (AA) oxidation and oxygen reduction in photocatalytic fuel cells. [Ru(ptp)2]2+ can be dissolved in ethanol (E), ethanol/water mixtures (M), or water (W) to produce three forms of aggregates, which are further assembled into [Ru(ptp)2]2+ modified CdS photoanodes. The MOF form of [Ru(ptp)2]2+-M shows the maximum absorbance at ethanol/water of 1:1 (Ve/Vw), and the resulting [Ru(ptp)2]2+-M/CdS electrode has better conductivity, larger light-harvesting efficiency and photovoltaic response compared with that of [Ru(ptp)2]2+-E/CdS. Furthermore, [Ru(ptp)2]2+-M exhibits enhanced photoelectrocatalytic activity towards ascorbate oxidation and oxygen reduction. The simultaneous presence of [Ru(ptp)2]2+-M on CdS photoanode and single-walled carbon nanotubes (SWCNTs) cathode used in visible light-excited ascorbate fuel cells, leads to a 1.1-fold or 4.5-fold increase in the open-circuit voltage or maximum power density. This present study provides a significant platform for solvent-dependent self-assembly of triazino-phenanthrene-containing metal complexes and improvement of photocatalytic fuel cell performances.