Nanostructured Indium Oxide Coated Silicon Nanowire Arrays: A Hybrid Photothermal/Photochemical Approach to Solar Fuels.
The field of solar fuels seeks to harness abundant solar energy by driving useful molecular transformations. Of particular interest is the photodriven conversion of greenhouse gas CO2 into carbon-based fuels and chemical feedstocks, with the ultimate goal of providing a sustainable alternative to traditional fossil fuels. Nonstoichiometric, hydroxylated indium oxide nanoparticles, denoted In2O3-x(OH)y, have been shown to function as active photocatalysts for CO2 reduction to CO via the reverse water gas shift reaction under simulated solar irradiation. However, the relatively wide band gap (2.9 eV) of indium oxide restricts the portion of the solar irradiance that can be utilized to ∼9%, and the elevated reaction temperatures required (150-190 °C) reduce the overall energy efficiency of the process. Herein we report a hybrid catalyst consisting of a vertically aligned silicon nanowire (SiNW) support evenly coated by In2O3-x(OH)y nanoparticles that utilizes the vast majority of the solar irradiance to simultaneously produce both the photogenerated charge carriers and heat required to reduce CO2 to CO at a rate of 22.0 μmol·gcat(-1)·h(-1). Further, improved light harvesting efficiency of the In2O3-x(OH)y/SiNW films due to minimized reflection losses and enhanced light trapping within the SiNW support results in a ∼6-fold increase in photocatalytic conversion rates over identical In2O3-x(OH)y films prepared on roughened glass substrates. The ability of this In2O3-x(OH)y/SiNW hybrid catalyst to perform the dual function of utilizing both light and heat energy provided by the broad-band solar irradiance to drive CO2 reduction reactions represents a general advance that is applicable to a wide range of catalysts in the field of solar fuels.
Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Laura B
LB
Hoch
Department of Mechanical Engineering, Lassonde School of Engineering, York University , Toronto, Ontario M3J 1P3, Canada.
Paul G
PG
O'Brien
Department of Materials Science and Engineering, University of Toronto , 184 College Street, Toronto, Ontario M5S 3E4, Canada.
Abdinoor
A
Jelle
Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Amit
A
Sandhel
Department of Materials Science and Engineering, University of Toronto , 184 College Street, Toronto, Ontario M5S 3E4, Canada.
Douglas D
DD
Perovic
Department of Chemical Engineering and Applied Chemistry, University of Toronto , 200 College Street, Toronto, Ontario M5S 3E5, Canada.
Charles A
CA
Mims
Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Geoffrey A
GA
Ozin
broadband solar irradiance; gas phase; indium oxide; photocatalysis; photothermal catalysis; silicon nanowires; solar fuels