Multimetallic Metasurfaces for Enhanced Electrocatalytic Oxidations in Direct Alcohol Fuel Cells

Abstract

Plasmonic metasurfaces enable unprecedented manipulation of light by using periodic arrangement of resonant unit cells or nanoantennas. Here, multimetallic metasurfaces made of self‐standing Ni/Au‐Pt nanostructured films are shown to significantly enhance an electrocatalytic oxidation reaction employed in direct alcohol fuel cells. The Ni/Au metasurfaces support photonic and plasmonic modes, which are leveraged for the site‐selective deposition of Pt electrocatalysts within the electromagnetic hot spots, where their reactivity can be strongly increased. The enhanced electrocatalytic activity for the methanol oxidation reaction (MOR) is primarily attributed to electronic effects due to the excitation of hot charge carriers and plasmonic near fields, as supported by electromagnetic simulations and kinetic isotopic experiments. Wavelength‐dependent photoelectrochemical investigations suggest that Ni/Au‐Pt metasurfaces enhances MOR over a broad spectral range and favors different light‐induced reaction mechanisms depending on the selected energy window.

Balancing Near-Field Enhancement and Hot Carrier Injection: Plasmonic Photocatalysis in Energy-Transfer Cascade Assemblies

“…In this manner, the charge recombination probability is also reduced as a result of the separation effect, to the benefit of the energy conversion efficiency and overall photocatalytic activity. , The addition of PNPs to the TiO 2 /QDs assemblies can further enhance the overall photocatalytic performance of the composites by increasing the charge carriers transferred. − One can also consider the QDs as a “bridge” between the PNPs and the TiO 2 NPs, in terms of both HEI and, perhaps more importantly, PET due to the more significant overlap between the PNP and QD spectra. This situation is in contrast with that of a metallic catalyst in interaction with the PNPs, in which PET is possible at broader wavelength ranges. − …”

Designing Metasurfaces for Efficient Solar Energy Conversion

“…208 The so-obtained Pt−Au/Ni metasurfaces were used for methanol oxidation in direct alcohol fuel cells, revealing a significant enhancement in electrocatalytic activity under light irradiation compared with a continuous Pt film deposited on the Au/Ni metasurfaces (Figure 8f). 208 Follow-up studies evidenced that catalytic Pd particles grown at the EM hot spots led to a higher catalytic activity and stability compared to the same photoanode where the NPs were grown in a homogeneous way on the whole surface area of the structure. 209 Metasurfaces have also been employed in photocatalytic arrangement, where no bias is applied, and the oxidation and reduction half-reactions occur at the solid−liquid interface of the same illuminated material in contact with the electrolyte (Figure 9a and Table S3 for additional details).…”

“…(f) Plasmonic Ni/Au–Pt metasurfaces for methanol oxidation applied in direct alcohol fuel cell. Adapted with permission from ref . Copyright 2022 Wiley-VCH GmbH.…”

“…Apart from water splitting, other processes can benefit greatly from the photonic designs brought by metasurfaces. For example, plasmonic metasurfaces consisting of Au/Ni nanopillars were used to grow Pt NPs as catalytic material on the electromagnetic hot spots (Figure f) . The so-obtained Pt–Au/Ni metasurfaces were used for methanol oxidation in direct alcohol fuel cells, revealing a significant enhancement in electrocatalytic activity under light irradiation compared with a continuous Pt film deposited on the Au/Ni metasurfaces (Figure f) .…”

Transmissive angle-multiplexed meta-polarizer based on a multilayer metasurface

“…Recently, metasurfaces, two-dimensional metamaterials constructed by planar meta-atoms with designable EM responses arranged in some specific global orders, have shown great capabilities to manipulate EM waves with many fascinating effects discovered [1][2][3] , including anomalous reflection/refraction [4][5][6] , meta-lensing [7][8][9] , polarization conversion [10][11][12][13] , meta-hologram [14][15][16][17] , surface-wave manipulations [18][19][20][21] , electromagnetically induced transparency [22] , and many others [23][24][25][26][27][28][29] . Since the metasurface is flat and ultra-thin, it forms an ideal platform to realize multifunctional EM devices.…”