Plasmonic enhancement of visible-light water splitting with Au–TiO2 composite aerogels

Abstract

We demonstrate plasmonic enhancement of visible-light-driven splitting of water at three-dimensionally (3D) networked gold-titania (Au-TiO2) aerogels. The sol-gel-derived ultraporous composite nanoarchitecture, which contains 1 to 8.5 wt% Au nanoparticles and titania in the anatase form, retains the high surface area and mesoporosity of unmodified TiO2 aerogels and maintains stable dispersion of the ~5 nm Au guests. A broad surface plasmon resonance (SPR) feature centered at ~550 nm is present for the Au-TiO2 aerogels, but not Au-free TiO2 aerogels, and spans a wide range of the visible spectrum. Gold-derived SPR in Au-TiO2 aerogels cast as films on transparent electrodes drives photoelectrochemical oxidation of aqueous hydroxide and extends the photocatalytic activity of TiO2 from the ultraviolet region to visible wavelengths exceeding 700 nm. Films of Au-TiO2 aerogels in which Au nanoparticles are deposited on pre-formed TiO2 aerogels by a deposition-precipitation method (DP Au/TiO2) also photoelectrochemically oxidize aqueous hydroxide, but less efficiently than 3D Au-TiO2, despite having an essentially identical Au nanoparticle weight fraction and size distribution. For example, 3D Au-TiO2 containing 1 wt% Au is as active as DP Au/TiO2 with 4 wt% Au. The higher photocatalytic activity of 3D Au-TiO2 derives only in part from its ability to retain the surface area and porosity of unmodified TiO2 aerogel. The magnitude of improvement indicates that in the 3D arrangement either a more accessible photoelectrochemical reaction interphase (three-phase boundary) exists or more efficient conversion of excited surface plasmons into charge carriers occurs, thereby amplifying reactivity over DP Au/TiO2. The difference in photocatalytic efficiency between the two forms of Au-TiO2 demonstrates the importance of defining the structure of Au[parallel]TiO2 interfaces within catalytic Au-TiO2 nanoarchitectures.

Surface Plasmon-Assisted Solar Energy Conversion

“…A cobalt-based oxygen evolution catalyst was deposited on the exposed Au sides, whereas Pt NPs were deposited on TiO 2 as reducing sides. Considering high surface areas for enhancing the activity of photoanodes, DeSario et al reported the preparation of gold-titania aerogels (3D Au/TiO 2 ) via the sol-gel method and investigated the performance in photoelectrochemical water splitting [173]. The synthesis contained the simultaneous gelation of colloidal alkanethiolate-stabilized Au nanoparticles in the Ti-precursor sol.…”

Synthesis of cube-like Ag/AgCl plasmonic photocatalyst with enhanced visible light photocatalytic activity

“…As a result, a tremendous effort has been made to explore visible lightdriven photocatalysts. Recently, nano-scale noble metals have received intense attention because of their localized surface plasmon resonance (LSPR) [6][7][8][9]. This is much favorable for the full use of sunlight and this kind of material is named as plasmonic photocatalyst.…”

The role of photonics in energy

“…For example, modification of TiO 2 with surface plasmon resonance (SPR) active gold (Au) nanoparticles has recently emerged as a viable strategy for enhancing visible light absorption. [236][237][238][239] PEC water splitting at TiO 2 PCs modified with 10-nm Au nanoparticles was enhanced by a factor of 2 relative to Au-modified nanocrystalline (but nonphotonic) TiO 2 films. 240 Alternative materials to TiO 2 for photocatalytic water splitting [194][195][196] also benefit from PC-enabled improvement of light utilization.…”