Role of an Inert Electrode Support in Plasmonic Electrocatalysis

Abstract

Direct loading of plasmonic nanostructures onto catalytically inert conductive support materials leads to the Schottky barrier-free architecture of the photocatalytic system. Such systems have recently attracted the attention of the research community as they permit collection of hot carriers independent of their energy when additional charge separation strategies are used. However, a systematic mechanistic investigation and description of the contribution of an inert conductive support to plasmonic electrocatalysis is missing. Herein, we systematically investigated the effect of the supporting electrode material on the observed photoinduced enhancement by comparing the photoelectrocatalytic properties of AuNPs supported on highly oriented pyrolytic graphite (HOPG) and indium tin oxide (ITO) electrodes using electrocatalytic benzyl alcohol (BnOH) oxidation as a model system. Upon illumination, only ∼(3 ± 1)% enhancement in catalytic current was recorded on the AuNP/ITO electrodes in contrast to ∼(42 ± 6)% enhancement on AuNP/HOPG electrodes. Our results showed that the local heating due to light absorption by the electrode material itself independent of localized surface plasmon effects is the primary source of the observed significant photoinduced enhancement on the HOPG electrodes in comparison to the ITO electrodes. Moreover, we demonstrated that an increased interfacial charge transfer at elevated temperatures and not faster reactant diffusion as suggested previously is the main source of the thermal enhancement. This work highlights the importance of the systematic evaluation of contributions of all parts, even if they are catalytically inert, to the light-induced facilitation of catalytic reactions in plasmonic systems.