Plasmonic nanoparticle-semiconductor composites for efficient solar water splitting

Abstract

Photoelectrochemical (PEC) water splitting is a promising technology that uses light absorbing semiconductors to convert solar energy directly into a chemical fuel (i.e., hydrogen). PEC water splitting has the potential to become a key technology in achieving a sustainable society, if high solar to fuel energy conversion efficiencies are obtained with earth abundant materials. This review article discusses recent developments and discoveries in the mechanisms by which the localized surface plasmon resonance (LSPR) in metallic nanoparticles can increase or complement a neighbouring semiconductor in light absorption for catalytic water splitting applications. These mechanisms can mitigate the intrinsic optical limitations of semiconductors (e.g., metal oxides) for efficient solar water splitting. We identify four types of enhancement mechanisms in the recent literature: (i) light scattering, (ii) light concentration, (iii) hot electron injection (HEI), and (iv) plasmon-induced resonance energy transfer (PIRET). (i) Light scattering and (ii) light concentration are light trapping mechanisms that can increase the absorption of light with energies above the semiconductor optical band-edge. These two mechanisms are ideal to enhance the absorption of promising semiconductors with narrow bandgap energies that suffer from limited absorption coefficients and bulk charge recombination. On the other hand, (iii) HEI and the recently discovered (iv) PIRET are mechanisms that can enhance the absorption also below the semiconductor optical band-edge. Therefore, HEI and PIRET have the potential to extend the light utilization to visible and near-infrared wavelengths of semiconductors with excellent electrochemical properties, but with large bandgap energies. New techniques and theories that have been developed to elucidate the above mentioned plasmonic mechanisms are presented and discussed for their application in metal oxide photoelectrodes. Finally, other plasmonic and non-plasmonic effects that do not increase the device absorption, but affect the electrochemical properties of the semiconductor (e.g., charge carrier transport) are also discussed, since a complete understanding of these phenomena is fundamental for the design of an efficient plasmonic NP-semiconductor water splitting device.<p>Funding Agencies|NWO (VENI project); Wenner-Gren Foundations; Swedish Research Council; Swedish Foundation for Strategic Research; Royal Swedish Academy of Sciences; AForsk Foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]</p

From active plasmonic devices to plasmonic molecular electronics

“…showed that hot electrons are involved in a number of oxidation reactions on plasmonic clusters of Ag nanocubes under low‐intensity visible light illumination. Many studies devoted to water splitting, hydrogen evolution and oxygen evolution were recently reported and reviewed …”

“…Many studies devoted to water splitting, hydrogen evolution and oxygen evolution were recently reported [49][50][51][52] and reviewed. 53 Plasmonic substrates have a potential for triggering specific reactions based on hot-electron and hot-hole charge transfer reactions. From an electrochemical point of view, this means that plasmon-induced electrochemistry is likely to become an important research field.…”

Plasmon‐Enhanced Solar Water Splitting on Metal‐Semiconductor Photocatalysts

“…(5) or (6) For the photoelectrochemicalc atalytic water splitting, the photocurrent on the photoelectrode is normally used to evaluate the activityo fc atalytic water splitting reactions, which is similart od irectly measuring the amount of evolved H 2 and O 2 . If the amounts of evolved H 2 and O 2 are even less than the amount of the photocatalyst, the TON can help us to clarify whether the reactions proceed photocatalytically.T urnover number is determined by the number of reacted molecules to the number of active sites.…”

“…[4,5] To give ac ontextual background, we begin by briefly describing the main process of water splitting on semiconductors,a nd the evaluation criteria of photocatalytic water splitting. [4,5] To give ac ontextual background, we begin by briefly describing the main process of water splitting on semiconductors,a nd the evaluation criteria of photocatalytic water splitting.…”

“…In the present review,w ef ocus on the most recent research advances in plasmonic photocatalytic water splitting, especially for pure photocatalysis, and basically avoid discussing those where photoelectrochemical (PEC) water splitting was described to facilitate photogenerated charge separation. [4,5] To give ac ontextual background, we begin by briefly describing the main process of water splitting on semiconductors,a nd the evaluation criteria of photocatalytic water splitting. This is followed by ad iscussion of the motivation for utilizingp lasmonic effectsi ns olarw ater splitting and the plasmon-enhanced mechanisms.…”