Photopotential and Polarization Characteristics of Ruthenizer Complex Sensitized TiO2 Electrode for Marine Microbial Fuel Cell

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
H. Nay Wunn, S. Motoda, and M. Morita (Tokyo University of Marine Science and Technology)
We have been studied the performance of TiO2 electrode which is assembled in Marine Microbial Fuel Cell (MMFC). To increase the performance of TiO2 electrode and to improve conversion efficiency from solar energy, dye sensitizing was introduced to TiO2 electrode. The dye used for this experiment is a Ruthenizer complex, Di-tetrabutylammonium cis- bis (isothiocyanato) bis (2, 2-bipyridyl-4, 4’-dicarboxylato) ruthenium (II), well known as N719 dye, which shows high reproducibility and stability performance in dye-sensitized solar cells (DSSC). We also tried forming of Hydroxyapatite (HAp) layer on TiO2 surface before dye sensitizing for the purpose of anchorage effect of dye on TiO2 surface. The measurement of photopotential and polarization property were carried out in the artificial seawater as an electrolyte which does not include the redox couple as a mediator.

Photopotential and polarization was measured with a standard calomel electrode (SCE) as a reference electrode under the irradiation of a 150 W Xenon Lamp, and a platinum electrode was used as a counter electrode for polarization curve. In the measurement of photopotential, the potential dropped to active direction when the light was turned on. Once it reached to the most active potential value, it went back to noble direction slightly for 5 to 15 minutes after the light was on. The change in photopotential after that duration became small and it tended to be stable for 2 hours. This behaviour of photopotential was similar in all measurement of test electrodes.

The amount of Ruthenizer after 2-hour measurement of photopotential became relatively smaller compared to that before measuring. This is because dye recombination with TiO2 electrons took place with artificial seawater electrolyte in the absence of a redox couple for dye regeneration. But, the photopotential of dye-sensitized TiO2 electrode with HAp layer showed more active than that without HAp. This showed good compatibility of HAp since it did not disturb the performance of photo-catalytic reaction of TiO2 and it may show the ion or electron selectivity between Ruthenizer and TiO2 phases. The polarization measurement showed no distinct effectiveness of Ruthenizer sensitizing on TiO2 surface other than suppressing the TiO2 photo-catalytic reaction.

As the results, Ruthenizer sensitizing on TiO2 electrode showed lower photo-catalytic effect by the recombination of oxidized Ruthenizer electron due to absence of a redox mediator. On the other hand, using HAp on TiO2 electrode for Ruthenizer sensitizing showed improvement in photopotential characteristics of TiO2 electrode.