Photoelectrolysis of water at second generation carbon modified (cm)-n-Fe 2O 3 films in a photoelectrochemical cell under solar simulated light and sunlight illuminations

Abstract

In this article the results of photoelectrolysis of water at second generation carbon modified (CM)-n-Fe 2O 3 films in a photoelectrochemical cell, CM-n-Fe 2O 3 {double pipe}Pt under solar simulated light and sunlight illuminations are given. The highest photoresponse for water splitting was observed for the flame made CM-n-Fe 2O 3 samples synthesized under optimum conditions at flame temperature of 850 °C and oxidation time of 15 minutes. At measured potential of 0.1 V/SCE the CM-n-Fe 2O 3 sample showed a photocurrent density of 4.8 mA cm -2 compared to 1.71 mA cm -2 for the electric oven made n-Fe 2O 3 under illumination intensity of 100 mW cm -2 from a solar simulator. For water splitting reaction the corresponding maximum photoconversion efficiencies of 3.1% and 1.46% were found for the flame made CM-n-Fe 2O 3 and electric oven made n-Fe 2O 3 respectively. This indicates more than two fold increase in photoconversion efficiency for the CM-n-Fe 2O 3 compared to regular n-Fe 2O 3. This enhanced photoresponse can be attributed to increase in conductivity; band gap lowering from 2.3 eV to 1.95 eV as well as increase in absorption coefficient of light in CM-n-Fe 2O 3. Under monochromatic light illumination a total photocurrent density 4.0 mA cm-2 and 3.7 mA cm-2 were observed under solar simulated light and sunlight illuminations respectively at the same measured potential of 0.0 V/SCE. This lower photocurrent density under sunlight illumination was due to absence of light below wavelength of 300 nm in the sunlight. This indicates that solar simulated light is 7.5% skewed towards UV region compared to sunlight. EDS and XRD results showed the presence of carbon in CM-n-Fe 2O 3 but not in n-Fe 2O 3. © 2012 by American Scientific Publishers.