Localized photodeposition of catalysts using nanophotonic resonances in silicon photocathodes

Abstract

Nanostructured semiconductors feature resonant optical modes that confine light absorption in specific areas called “hot spots”. These areas can be used for localized extraction of the photogenerated charges, which in turn could drive chemical reactions for synthesis of catalytic materials. In this work, we use these nanophotonic hot spots in vertical silicon nanowires to locally deposit platinum nanoparticles in a photo-electrochemical system. The tapering angle of the silicon nanowires as well as the excitation wavelength are used to control the location of the hot spots together with the deposition sites of the platinum catalyst. A combination of finite difference time domain (FDTD) simulations with scanning electron microscopy image analysis showed a reasonable correlation between the simulated hot spots and the actual experimental localization and quantity of platinum atoms. This nanophotonic approach of driving chemical reactions at the nanoscale using the optical properties of the photo-electrode, can be very promising for the design of lithography-free and efficient hierarchical nanostructures for the generation of solar fuels.

Renewable energy conversion using nano- and microstructured materials

“…The Beilstein Journal of Nanotechnology thematic issue “Nano- and microstructures for energy conversion: materials and devices” provides insights into the latest developments in the related fields. Besides a focus on solar-cell concepts [1–5], it also addresses light harvesting by solar fuel production [6–7], and energy storage by batteries [8].…”

“…Nanostructured materials can be synthesized by a huge variety of approaches, extending from self-assembled structures [9], over various lithographic techniques [10] and imprinting methods [11], to different crystallization routes [12]. The thematic issue “Nano- and microstructures for energy conversion: materials and devices” covers the photo-electrochemical growth of platinum catalysts at plasmonic hot spots [6], the laser-assisted local growth of chalcopyrite absorbers [4], the preferential reactive ion etching of silicon by morphological anisotropies [5], the oxidation of copper nanoparticles resulting in nanoporous cobalt oxide photocathodes [7], and an approach in which silicon nanoparticles are embedded in an amorphous carbon matrix [8].…”