Charge generation dynamics in hematite photoanodes decorated with gold nanostructures under near infrared excitation

Enhancing photoelectrochemical water splitting with plasmonic Au nanoparticles

The water-based renewable chemical energy cycle has attracted interest due to its role in replacing existing non-renewable resources and alleviating environmental issues. Utilizing the semi-infinite solar energy source is the most appropriate way to sustain such a water-based energy cycle by producing and feeding hydrogen and oxygen. For production, an efficient photoelectrode is required to effectively perform the photoelectrochemical water splitting reaction. For this purpose, appropriately engineered nanostructures can be introduced into the photoelectrode to enhance light-matter interactions for efficient generation and transport of charges and activation of surface chemical reactions. Plasmon enhanced photoelectrochemical water splitting, whose performance can potentially exceed classical efficiency limits, is of great importance in this respect. Plasmonic gold nanoparticles are widely accepted nanomaterials for such applications because they possess high chemical stability, efficiently absorb visible light unlike many inorganic oxides, and enhance light-matter interactions with localized plasmon relaxation processes. However, our understanding of the physical phenomena behind these particles is still not complete. This review paper focuses on understanding the interfacial phenomena between gold nanoparticles and semiconductors and provides a summary and perspective of recent studies on plasmon enhanced photoelectrochemical water splitting using gold nanoparticles.

The effect of the photochemical environment on photoanodes for photoelectrochemical water splitting

Besides photoelectrode materials, realizing the synergy of the photochemical environment and photoelectrodes for high charge carrier utilization is crucial for enhancing the performance of photoelectrochemical (PEC) water splitting systems. However, few researchers have focused on this important aspect. Herein, the effect of the photochemical environment on photoanodes in PEC water splitting, including the redox potential of electrolytes and light direction, is rationally discussed. A combined study of the potential distribution and electrochemical impedance spectroscopy reveals that the low redox potential of electrolytes facilitates the interior charge transfer and surface charge utilization by enlarging the depletion layer. In addition, it is found that the optimum thickness of semiconductors in photoelectrodes is the length of the depletion layer plus diffusion layer.

Special topic on emerging directions in plasmonics

Plasmonics enables a wealth of applications, including photocatalysis, photoelectrochemistry, photothermal heating, optoelectronic devices, and biological and chemical sensing, while encompassing a broad range of materials, including coinage metals, doped semiconductors, metamaterials, 2D materials, bioconjugates, and chiral assemblies. Applications in plasmonics benefit from the large local electromagnetic field enhancements generated by plasmon excitation, as well as the products of plasmon decay, including photons, hot charge carriers, and heat. This special topic highlights recent work in both theory and experiment that advance our fundamental understanding of plasmon excitation and decay mechanisms, showcase new applications enabled by plasmon excitation, and highlight emerging classes of materials that support plasmon excitation.