Metasurface Photoelectrodes for Enhanced Solar Fuel Generation

Tailoring optical properties in photocatalysts by nanostructuring them can help increase solar light harvesting efficiencies in a wide range of materials. Whereas plasmon resonances are widely employed in metallic catalysts for this purpose, latest advances of nonradiative, dielectric nanophotonics also enable light confinement and enhanced visible light absorption in semiconductors. Here, a design procedure for large-scale nanofabrication of semiconductor photoelectrodes using imprint lithography is developed. Anapole excitations and metasurface lattice resonances are combined to enhance the absorption of the model material, amorphous gallium phosphide (a-GaP), over the visible spectrum. It is shown that cost-effective, high sample throughput is achieved while retaining the precise signature of the engineered photonic states. Photoelectrochemical measurements under hydrogen evolution reaction conditions and sunlight illumination reveal the contributions of the respective resonances and demonstrate an overall photocurrent enhancement of 5.7, compared to a planar film. These results are supported by optical and numerical analysis of single nanodisks and of the upscaled metasurface.

Automated summary

Tailoring the optical properties of photocatalysts through nanostructuring can enhance solar light harvesting efficiencies, with imprint lithography developed for large-scale fabrication of semiconductor photoelectrodes. The combination of anapole excitations and metasurface lattice resonances improves the absorption efficiency of model materials over the visible spectrum, leading to a significant enhancement of photocurrent under solar illumination conditions.