Plasmonic photocatalysis applied to solar fuels

• Published in: Faraday discussions Vol. 214; pp. 417 - 439
• Main Authors: Bardey, Steven, Bonduelle-Skrzypczak, Audrey, Fécant, Antoine, Cui, Zhenpeng, Colbeau-Justin, Christophe, Caps, Valérie, Keller, Valérie
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 23.05.2019
• Subjects: Catalysis; Chemical Sciences
• ISSN: 1359-6640; 1364-5498
• DOI: 10.1039/c8fd00144h

The induction of chemical processes by plasmonic systems is a rapidly growing field with potentially many strategic applications. One of them is the transformation of solar energy into chemical fuel by the association of plasmonic metal nanoparticles (M NPs) and a semi-conductor (SC). When the localized surface plasmon resonance (LSPR) and the SC absorption do not match, one limitation of these systems is the efficiency of hot electron transfer from M NPs to SC through the Schottky barrier formed at the M NP/SC interfaces. Here we show that high surface area 1 wt% Au/TiO 2-UV100 , prepared by adsorption of a NaBH 4 -protected 3 nm gold sol, readily catalyzes the photoreduction of carbon dioxide with water into methane under both solar and visible-only irradiation with a CH 4 vs. H 2 selectivity of 63%. Tuning Au NP size and titania surface area, in particular via thermal treatments, highlights the key role of the metal dispersion and of the accessible Au-TiO 2 perimeter interface on the direct SC-based solar process. The impact of Au NP density in turn provides evidence for the dual role of gold as co-catalyst and recombination sites for charge carriers. It is shown that the plasmon-induced process contributes up to 20% of the solar activity. The plasmon-based contribution is enhanced by a large Au NP size and a high degree of crystallinity of the SC support. By minimizing surface hydroxylation while retaining a relatively high surface area of 120 m 2 g −1 , pre-calcining TiO 2-UV100 at 450 °C leads to an optimum monometallic system in terms of activity and selectivity under both solar and visible irradiation. A state-of-the-art methane selectivity of 100% is achieved in the hot electron process. We show the impact of structural, chemical and interfacial features of gold-titania composites on solar and visible photocatalytic gas phase reduction of CO 2 and the specificities of the hot electron-based process.