Oligomeric Ruthenium Polypyridyl Dye for Improved Stability of Aqueous Photoelectrochemical Cells

Abstract

Water-splitting dye-sensitized photoelectrochemical cells rely on molecular sensitizers to harvest light energy and drive the catalytic reactions necessary to generate hydrogen and oxygen from water. The desorption of sensitizer molecules from the semiconductor−aqueous electrolyte interface is a significant barrier to the practical implementation of these cells. To address this problem, we synthesized an oligomeric ruthenium dye ([RuP] n ) that has dramatically improved stability as a photosensitizer for TiO 2 electrodes over the pH range of interest (4−7.8) for DSPECs. Additionally, the efficiency of photoelectrochemical charge separation is known to depend on the rate of cross-surface hole diffusion between dye molecules. The oligomeric dye ([RuP] n ) shows an order of magnitude faster cross-surface hole diffusion than the commonly used monomeric [Ru(bpy) 2 (4,4-PO 3 H 2 ) 2 bpy] 2+ (RuP) sensitizer. The enhanced stability of the polymeric dye also enables the use of intensity-modulated photovoltage spectroscopy to measure the recombination rate of photogenerated electrons and holes as a function of electrolyte pH.Article pubs.acs.org/JPCC

Metal Complexes for Dye-Sensitized Photoelectrochemical Cells (DSPECs)

“…In addition, 8 was stable in a neutral (pH 7) or basic (pH 9) aqueous buffer solution, clearly suggesting that the pyridyl anchoring moiety is likely a more suitable choice for photocatalytic applications under a water medium. A recent strategy was achieved by Mallouk by employing a phosphonate oligomeric ruthenium dye (11) [65], which resulted in a dramatically improved electrode adhesion in the range of pH between 4 and 7.8. The authors highlighted a faster cross-surface hole diffusion for the multinuclear species (≈ one order of magnitude) if compared to the monomeric one.…”

Organic Semiconductors as Photoanodes for Solar-driven Photoelectrochemical Fuel Production

“…In addition to the OERC, another factor which affected the stability was the photosensitizer itself. It is hypothesized that in DS-PECs, the loss of stability is primarily due to detachment of the dye from the metal oxide, [78,79] or the oxidative decomposition of the chromophore. [72,76] To address these issues, additional protective overlayers were used to enhance the stability.…”

Organic Semiconductors for Photoelectrochemical Applications

“…In addition to the OERC, another factor which affected the stability was the photosensitizer itself. It is hypothesized that in DS-PECs, the loss of stability is primarily due to detachment of the dye from the metal oxide [92,93] or the oxidative decomposition of the chromophore. [85,89] To address these issues, additional protective overlayers were used to enhance the stability.…”