Abstract
AbstractPhotocatalysis using semiconductor materials like titania (TiO2) is a key method for environmental purification or solar fuel generation. Nanostructures that maximize incident light absorption are highly desired to enhance depollution rate or solar‐to‐fuel conversion efficiency in limited volumes of catalysts. Here, we report on structural and optical properties of metasurfaces based on a 20 nm thick anatase layer conformally deposited onto a wavelength‐scale two‐dimensional periodic photonic lattice. We investigate the NO degradation using such metasurfaces, and evaluate the impact of the patterning on photocatalytic activities between 340 and 400 nm. In the 380–385 nm range, the mean photochemical efficiency is increased by a factor up to 5.7 compared to flat references, with an overall three‐fold enhancement within the whole spectral range of interest. This approach can be applied to numerous types of systems by varying active materials, leading to substantial improvements in air/water depollution, water splitting or artificial photosynthesis processes.
Highlights
Semiconductor based photocatalysis is generating considerable interest as a mean to tackle current challenges such as depollution and solar energy conversion.[1]
As a case-study, the photocatalytic depollution reaction NO + 1/2O2 + H2O + UV → NO2 + H2O was performed on the A and B-type two dimensional metasurfaces, and on planar references
We have demonstrated the combined effect of UV light trapping and surface area enhancement on the efficiency of photocatalysis, using photonic metasurfaces combining a transparent two dimensional photonic lattice and a highly conformal TiO2 active layer
Summary
Semiconductor based photocatalysis is generating considerable interest as a mean to tackle current challenges such as depollution and solar energy conversion.[1]. They are generally realized on the basis of a three dimensional periodic assembly of silica or polymeric sub-micron spheres, subsequently infiltrated by materials that exhibit relevant optical and catalytic properties This approach was investigated with a view to develop structures such as plasmonic-photonic[23] or photonic crystal[24] heterostructures assisting photocatalysis, or metal loaded TiO2 inverted opals dedicated to photocatalytic reduction of CO2.[25] fabricating such complex three dimensional structures is costly and based on very low throughput processes. We propose to generate a two dimensional metasurface including a simple and transparent photonic lattice with wavelength-scale patterns, which can be realized by high throughput processes like nanoimprint This photonic lattice acts as a light trapping medium; it can be covered by an absorbing layer acting as the photocatalyst with a thickness well below the optical wavelength so as to inhibit photocarrier recombination. This light trapping assisted by slow light is proposed as an efficient strategy to enhance various kinds of photocatalytic processes that would contribute to air or water depollution, like in the case of NO oxidation, or generate solar fuels with more complex catalysts
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