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Spray pyrolysis deposition and photoelectrochemical properties of n-type BiOI nanoplatelet thin films.

ACS nano (2012-08-16)
Nathan T Hahn, Son Hoang, Jeffrey L Self, C Buddie Mullins
ABSTRACT

Bismuth oxy-iodide is a potentially interesting visible-light-active photocatalyst; yet there is little research regarding its photoelectrochemical properties. Herein we report the synthesis of BiOI nanoplatelet photoelectrodes by spray pyrolysis on fluorine-doped tin oxide substrates at various temperatures. The films exhibited n-type conductivity, most likely due to the presence of anion vacancies, and optimized films possessed incident photon conversion efficiencies of over 20% in the visible range for the oxidation of I(-) to I(3)(-) at 0.4 V vs Ag/AgCl in acetonitrile. Visible-light photons (λ > 420 nm) contributed approximately 75% of the overall photocurrent under AM1.5G illumination, illustrating their usefulness under solar light illumination. A deposition temperature of 260 °C was found to result in the best performance due to the balance of morphology, crystallinity, impurity levels, and optical absorption, leading to photocurrents of roughly 0.9 mA/cm(2) at 0.4 V vs Ag/AgCl. Although the films performed stably in acetonitrile, their performance decreased significantly upon extended exposure to water, which was apparently caused by a loss of surface iodine and subsequent formation of an insulating bismuth hydroxide layer.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Bismuth(III) oxide, ReagentPlus®, powder, 10 μm, 99.9% trace metals basis
Sigma-Aldrich
Bismuth(III) oxide, powder, 99.999% trace metals basis
Sigma-Aldrich
Bismuth(III) iodide, 99%
Sigma-Aldrich
Bismuth(III) oxide, nanopowder, 90-210 nm particle size, 99.8% trace metals basis
Sigma-Aldrich
Bismuth(III) iodide, ≥99.998% trace metals basis
Sigma-Aldrich
Bismuth(III) oxide, purum, ≥98.0% (KT)