Plasmonic stimulated photocatalytic/electrochemical hydrogen evolution from water by (001) faceted and bimetallic loaded titania nanosheets under sunlight irradiation

Abstract

This study demonstrates the synthesis of TiO2 nanosheets (TNST) exhibiting high percentage (54%) of exposed (001) facets and decorated with co-deposited gold and platinum nanoparticles (NPs). The as synthesized as well as modified sheets are then investigated for the photo-reduction of water under sunlight irradiation using different alcohols as hole-scavengers. Structural and morphological studies manifest the formation of well-defined sheet structure of TiO2 with average dimensions of 55 nm × 46 nm. The measured d spacing of 0.34 nm and 0.23 nm corresponds to (101) and (001) facets of anatase TiO2. The presence of Au and Pt was confirmed by electron diffraction and X-ray photoelectron spectroscopy. TiO2 nanosheets (TNST's) with 0.4 and 0.75 wt % of Au and Pt (Au0.4/Pt0.75-TNSTs), respectively were found to exhibit higher efficiency. Furthermore, photo-electrochemical (PEC) water splitting studies revealed the increase in photocurrent from 2 mA at 0.5 V to 4.5 mA at 0.65 V for Au0.4/Pt0.75-TNST photoelectrodes, which otherwise was 0.15 mA for the bare TNST photoelectrodes at the same potential. The observed PEC performance was well supported by impedance analysis, wherein Au0.4/Pt0.75-TNSTs (338 Ω) are found to exhibit lower resistance in comparison to bare TNST (737 Ω), which could be due to brilliant photo conductance and interfacial charge transfer properties of Au0.4/Pt0.75-TNSTs. Photocatalytically the Au0.4/Pt0.75-TNST produced ∼143 μmol h1 of H2 gas under direct sunlight irradiation, which is found equivalent to 16.1% apparent quantum efficiency.