Understanding the effect of plasmonic enhancement on photocatalytic activity of TiO2 nanotube arrays

Plasmonic effects in wide-bandgap photocatalysts loaded with noble metal nanoparticles (NPs) have been shown to enhance visible light absorption as well as charge transfer. TiO2 owing to its superior photostability, abundance and non-toxcitiy, especially in form of nanotube arrays (NTAs) to maximize surface interactions, has been often used as a photoactive template. However systematic studies of photoelectrochemical properties in plasmonic TiO2 NTAs are rare and usually involve Au NPs only. Here, we examine the effect of Ag NP loading of TiO2 NTAs via photoreduction of different concenrations of AgNO3 (20 mM-1100 mM) in order to establish the optimum value at which photoactivity is maximal. Remarkably, the system prepared from 200 mM aqueous solution were found to exhibit an unprecedented 680-fold increase in photocurrent density as compared to the bare anatase NTAs (0.041 mA.cm(-2) versus 0.06 mu A.cm(-2)). Furthermore, hydrogen evolution under AM 1.5G illumination was improved by 350% from 40 mu L.cm(-2) in pristine anatase NTAs to 180 mu L.cm(-2) in optimally decorated NTAs.