Porous Plasmonic Au-Ag@Au Nanostructures for Photoelectrochemical Methanol Oxidation

Pt and its alloys are commonly used as catalysts for electrochemical methanol oxidation reaction (MOR), owing to their high efficiencies. However, the high cost and instability of these catalysts due to poisoning from intermediates restrict their large-scale applications. Here we study plasmonic porous Au-Ag nanoparticles toward electrochemical and photoelectrochemical MOR. We synthesized Au-Ag@Au nanostructures that consist of the Au nanorod core and Au-Ag shell, where nanopores were created via selectively etching Ag atoms. The porous Au-Ag@Au nanostructures demonstrated significantly better MOR activity compared to their nonporous counterpart. Importantly, the presence of pores drastically suppressed the poisoning from the intermediate species, leading to a large improvement of their electrochemical stability. Furthermore, the porous Au-Ag@Au constructs showed strong enhancement of their catalytic activity under visible as well as near-infrared (NIR) excitations with generation of photocurrents of 1.23 and 0.45 mA mg-1 cm2, and with incident photon to current conversion efficiencies of 1.43 and 0.34% for visible and NIR wavelengths, respectively. Generation of photocurrents was shown to be predominantly due to the plasmonic hot-hole-assisted MOR.