Multimetallic Metasurfaces for Enhanced Electrocatalytic Oxidations in Direct Alcohol Fuel Cells

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.