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SURFACE-CHARGE-ENABLED PHOTOLYTIC HYDROGEN GENERATION IN V2O5·H2O/Au NANOCONJUGATES

Published online by Cambridge University Press:  20 April 2016

Sunith Varghese ,
Charuksha Walgama ,
Mark Wilkins ,
Sadagopan Krishnan  and
Kaan Kalkan
Sunith Varghese
Affiliation:
Functional Nanomaterials Laboratory, Oklahoma State University, Stillwater, OK, USA
Charuksha Walgama
Affiliation:
Chemistry Department, Oklahoma State University, Stillwater, OK, USA
Mark Wilkins
Affiliation:
Biosystems/Agricultural Engineering, Oklahoma State University, Stillwater, OK, USA
Sadagopan Krishnan
Affiliation:
Chemistry Department, Oklahoma State University, Stillwater, OK, USA
Kaan Kalkan*
Affiliation:
Functional Nanomaterials Laboratory, Oklahoma State University, Stillwater, OK, USA
*
*(Email: kaan.kalkan@okstate.edu)
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Abstract

The present work investigates sol-gel synthesized vanadium oxyhydrate (V2O5·H2O) nanowires decorated with Au nanoparticles as potential photolytic H2 generators. As determined by UV photoelectron and optical spectroscopies, the conduction band edge of V2O5·H2O lies 0.6 eV below standard H+ reduction potential, implying no H2 can be generated. On the contrary, as measured by gas chromatography, our nanoconjugates yield reproducible light-to-hydrogen conversion efficiency of 5.3%, for the first hour of photolysis under 470 nm excitation. To explain the observed hydrogen reduction, we have hypothesized the vanadia electron energy levels are raised by some negative surface charge. With the objective of validating this hypothesis, we have performed cyclic current-voltage measurements. The derived conduction and valence band edge energies are not only consistent with the optical band gaps, but also validate the hypothesized energy increase by 1.6 eV, respectively. The negative surface charge is also corroborated by the ζ-potential. Based on the measured pH of 2.4, we attribute the negative surface charge to Lewis acid nature of the nanowires, establishing dative bonding with OH−. The present work establishes the importance of surface charge in photoelectrochemical reactions, where it can be instrumental and enabling in photolytic fuel production.

Keywords

energetic materialnanostructureH
Type
Articles
Information
MRS Advances , Volume 1 , Issue 46: Energy and Environment , 2016 , pp. 3121 - 3126
Copyright
Copyright © Materials Research Society 2016 

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References

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