Dibenzyldithiocarbamate-Functionalized Small Gold Nanoparticles as Selective Catalysts for the Electrochemical Reduction of CO2 to CO

Abstract

Dibenzyldithiocarbamate-functionalized gold nanoparticles (DBDTC-Au NPs) were synthesized in the laboratory, and the effects of the DBDTC ligand on the Au electrocatalytic activity for CO2 reduction reaction to CO were investigated in CO2-saturated KHCO3 electrolyte. Our synthesis route produced sub-2.0 nm Au particles, with the number of gold atoms in the range of 67–120, and with strongly bonded and stable DBDTC ligands on the surface. Online differential electrochemical mass spectrometry (DEMS) experiments on the DBDTC-Au nanoparticles showed higher faradic current and higher CO/H2 ratio of their ionic signals compared to those for citrate-capped Au NPs. Quantitative analyses via gas chromatography (GC) showed that our DBDTC-Au catalyst converts CO2 into CO with a faradic efficiency of approximately 100 ± 1% at −0.8 V and 93 ± 0.5% at −1.0 V vs RHE. The higher activity of the synthesized DBDTC-Au electrocatalyst was attributed to the following important functionalities of the DBDTC ligand: (i) the strong bonding to the surface stabilizes the Au NPs, inhibiting the formation of large agglomerates, and (ii) the hydrophobic character of the dibenzyl moieties allows the permeation of CO2, but repels water from the Au surface, minimizing the electrochemical reduction of water and, therefore, enhancing the faradic efficiency for CO formation.