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Harnessing Visible Light and Limited Near IR Photons Through Plasmon Effect of Gold Nanorod with AgTiO2 Kshirodra Kumar Patra, and Chinnakonda S. Gopinath J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b10289 • Publication Date (Web): 18 Dec 2017 Downloaded from http://pubs.acs.org on December 18, 2017
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The Journal of Physical Chemistry
Harnessing Visible Light and Limited Near IR Photons Through Plasmon Effect of Gold Nanorod with AgTiO2 Kshirodra Kumar Patra,a and Chinnakonda S. Gopinatha,b,c,* a
Catalysis Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India.
b
Centre of Excellence on Surface Science, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India.
c
Network of Institutes for Solar Energy (NISE), NCL Campus, Pune 411 008, India.
*Author for correspondence: Email:
[email protected]; Ph: 0091-20-25902043
ABSTRACT: The utilization of the red-green-blue (RGB) and limited near IR photons for solar hydrogen evolution (SHE) has been reported in a single plasmonic nanocomposite. Present study describes the use of AgTiO2 (AgT) decorated with Au nanorods (AgT-AuNR) to enhance the absorption of entire visible light and limited near IR wavelength range in the sunlight for SHE from photocatalytic water splitting reaction. It is demonstrated that the longitudinal plasmon resonance of AuNR in AgT-AuNR induces SHE between 550 and 800 nm, whereas TiO2-AuNR or AgT shows no activity in this wavelength range. The key aspect of achieving the high photocatalytic activity of AgT-AuNR in the solar spectrum is the electronic integration among metal NPs as well as with TiO2, and the heterojunctions among them. Presence of such heterojunctions has been supported by different characterization studies. However, gold nanorod exhibits field effect and further enhances light harvesting. Although the absolute amount of energy harvested only from near IR photons is low, when combined with high energy visible light photons within one sun conditions, it shows a multiplier effect rather than a simple additive effect. Likely, this is the first report, where SHE has been achieved with significant amount of light absorption at λ ≥ 550 nm with a plasmonic nanocomposite.
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INTRODUCTION In the not-so-distant future, photocatalytic solar hydrogen evolution (SHE) could become one of the promising method for solar light harvesting towards the production of carbon free clean fuel such as hydrogen, and reduction of CO2 to fuels/chemicals.1-3 Among the many semiconductors, TiO2 is the most extensively studied semiconductor due to its rightly positioned valence band (VB) and conduction band (CB) for oxidation and reduction half reactions of water, respectively.4,5 However, TiO2 has a critical limitation, which is the limited light absorption to UV region (≤ 380 nm) and hence an effective utilization of sunlight was not possible.6 Many strategies were developed to overcome this limitation, such as sensitizing wide band gap TiO2 with a narrow band gap semiconductor, like CdS, CdSe, and by doping metal and non-metal ions.7-9 Apart from this, very less work has been reported on the utilization of the visible light with high λ or low photon energy (λ ≥ 550 nm) and near IR (up to 1000 nm), which constitute almost half of solar spectrum for photocatalytic solar water splitting (SWS) reaction. Cui et al has reported a WO2NaxWO3 hybrid material for IR driven photocatalytic hydrogen evolution.10 This hybrid absorbs only near IR region and hence the activity is very low for SHE. Stucky et al. demonstrated the plasmon enhanced hydrogen evolution of 11.6 µmol h-1g-1 in visible + NIR light with AuNR-TiO2 nanocomposite system.11 The direct utilization of the photons available (
