New Transparent Laser-Drilled Fluorine-doped Tin Oxide covered Quartz Electrodes for Photo-Electrochemical Water Splitting

Significance Statement

 Photo-catalytic water-splitting, also known as “artificial photosynthesis”, offers a promising way for clean, low-cost and environmentally friendly production of H2 by solar energy. Current research on this field focus, on one side, on improving  the photo-catalyst materials and, on the other,  on developing low cost integrated devices for the direct solar-to-fuel conversion.

Thanks to a collaboration between teams from Politecnico di Torino, Istituto Italiano di Tecnologia (IIT@POLITO) and Solaronix SA, an efficient and small scale device for testing H2 production through water splitting has recently been fabricated. The design and the technologies employed in the device fabrication, together with the results obtained on new transparent laser-drilled Fluorine-doped Tin Oxide (FTO)-covered quartz electrodes, were recently reported by Hernández et. al. in: Electrochimica Acta 131, 2014, 184-194. In such work, quartz slides (350 um-thick, 2.5 x 2.2 cm2) have been covered by thin films of FTO (40 Ω/sq) and subsequently laser-treated in order to obtain a region (1 x 1 cm2) with an array of holes permitting the permeation of water and gas molecules. This groundbreaking transparent, conductive and porous electrode constitutes an optimun support for photo-active materials: it allows the flow of the produced gases, the mobility of protons (H+) through the electrolyte, the collections of generated electrons (through FTO) and the application of a bias voltage. The FTO-drilled electrodes have been successfully employed as a support for TiO2 nanoparticles, coupled with a polymeric electrolyte membrane and a Pt electrode to obtain a transparent membrane electrode assembly (MEA), which has a good conductivity, wettability and porosity.

Photoelectochemical and electrochemical analysis have been employed to study the main charge transfer and transport phenomena’s behaving in the system, which evidenced that this new electrode architecture is an ideal support for testing new anodic and cathodic photoactive materials, working in tandem configuration for solar fuels production by water photo-electrolysis.

 

New Transparent Laser-Drilled Fluorine-doped Tin Oxide covered Quartz Electrodes for Photo-Electrochemical Water Splitting. Advances In Engineering

 

 

 

 

 

 

 

Journal Reference

Electrochimica Acta, Volume 131, 2014, Pages 184-194. Simelys Hernández1, , Mauro Tortello2, Adriano Sacco1, Marzia Quaglio1, Toby Meyer3, Stefano Bianco1, Guido Saracco2, C. Fabrizio Pirri1, 2, Elena Tresso1, 2

[expand title=”Show Affiliations”]

1 Center for Space Human Robotics, IIT@POLITO, Istituto Italiano di Tecnologia, C.so Trento 21, 10129, Turin, Italy and

2 Department of Applied Science and Technology (DISAT), Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129, Turin, Italy and

3 Solaronix SA, Rue de l’Ouriette 129, CH-1170, Aubonne VD, Switzerland

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Abstract

A new-designed transparent, conductive and porous electrode was developed for application in a compact laboratory-scale proton exchange membrane (PEM) photo-electrolyzer. The electrode is made of a thin transparent quartz sheet covered with fluorine-doped tin oxide (FTO), in which an array of holes is laser-drilled to allow water and gas permeation. The electrical, morphological, optical and electrochemical characterization of the drilled electrodes is presented in comparison with a non-drilled one. The drilled electrode exhibits, in the visible region, a good transmittance (average value of 62%), a noticeable reflectance due to the light scattering effect of the hole-drilled internal region, and a higher effective surface area than the non-drilled electrode. The proof-of-concept of the applicability of the drilled electrode was achieved by using it as a support for a traditional photocatalyst (i.e. commercial TiO2 nanoparticles). The latter, coupled with a polymeric electrolyte membrane (i.e.Nafion 117) and a Pt counter electrode, forms a transparent membrane electrode assembly (MEA), with a good conductivity, wettability and porosity. Electrochemical impedance spectroscopy (EIS) was used as a very powerful tool to gain information on the real active surface of the new drilled electrode and the main electrochemical parameters driving the charge transfer reactions on it. This new electrode architecture is demonstrated to be an ideal support for testing new anodic and cathodic photoactive materials working in tandem configuration for solar fuels production by water photo-electrolysis.

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