Strategies for Plasmonic Hot‐Electron‐Driven Photoelectrochemical Water Splitting

Abstract

Photoelectrochemical water splitting (PEC‐WS) was inspired by the natural photosynthesis process that utilizes sunlight energy to produce chemical energy through splitting water to form hydrogen and oxygen. One recent promising and innovative approach in this field is to implement the concept of plasmonic to PEC‐WS devices. This Review provides a systematic overview of the plasmonic and hot‐electron‐driven PEC‐WS and elucidates their possible mechanisms for plasmon‐mediated energy transfer. In the first section, we provide a brief summary of the basics of PEC‐WS and the strategies employed to maximize its conversion efficiency. Highlighting the advantages of the plasmonic‐based PEC system, in the next part we cluster our discussion based on the basics of plasmonics and the involved energy transfer mechanisms, which are classified as radiative (scattering, optical near field coupling) and nonradiative energy transfer (hot electron injection, plasmon resonant energy transfer) processes for plasmonic metal–semiconductor junctions as a photoactive material. Then, the recent research efforts in this field are categorized and discussed in three main sections: 1) nanoplasmonic units, 2) nanostructured support scaffolds, and 3) interface engineering with state‐of‐the‐art demonstrations. Finally, we conclude our Review with pointing out the challenges and perspectives of the plasmonic‐based architectures for future water‐splitting devices.

Semiconductor Thin Film Based Metasurfaces and Metamaterials for Photovoltaic and Photoelectrochemical Water Splitting Applications

“…Upon the excitation of localized surface plasmons in metal–semiconductor interface, its energy can be transferred to the adjacent semiconductor via two main pathways; 1) radiative and 2) nonradiative energy transfer . In the radiative energy process, the subwavelength metal particle acts like an antenna where excited hot electrons relax into lower energy states and reradiate as a secondary source.…”

“…It should be noted that this property can be tuned by the refractive index of surrounding medium, composition, and the wavelength. Scattering could be found in both metal and dielectric nanostructures and it mainly improves light trapping by maximizing the optical path of the light within the semiconductor . The second process is named near field coupling and it takes the main role in the energy transfer process for smaller plasmonic particles.…”

“…Upon irradiation of the metal–semiconductor junction, the localized surface plasmon resonance (LSPR) gets excited. The nonradiative decay of these LSPRs will generate hot electrons . Most of these hot electrons have energetic location close to the metal Fermi level ( E f ) and just a small portion of them can have required energy to overcome the Schottky barrier at the metal–semiconductor interface and contribute to the overall photocurrent .…”

“…This could be obtained by utilizing the scattering property of large metal nanoparticles. The scattering cross section of these metallic nanoparticles can be tuned by particles' type, shape, size, distance from the semiconductor and the surrounding environment permittivity . For instance, it has been found that cylindrical Ag particles can scatter a higher fraction of indent light into the underlying active layer compared to spherical shapes .…”

Strong Light–Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting

“…Unlike semiconductors, which only harvest photon energies above their band gap, nanometals exhibit resonant light absorption in the whole electromagnetic spectrum, through the excitation of localized surface plasmon resonances (LSPRs) and inter‐band transitions. Thus, plasmonic photoelectrochemical water splitting (PEC‐WS) offers a promising approach to convert sunlight into chemical energy, which has recently received intense research . Plasmonic nanometals can contribute to the semiconductor activity enhancement through two main pathways; i) radiative (scattering, optical near field coupling) and ii) non‐radiative energy transfer (hot electron injection, plasmon resonant energy transfer) .…”