Surface Modification of Three-Dimensional Au Coated Polymer Electrodes for Electrochemical Reduction of CO2
Authors: Rakhsha Amirhossein , Ismail Fatma , Abdellah Ahmed , Soleymani Leyla , Higgins Drew 
Published: July 2022

Electrochemical reduction of CO2 (CO2R) into chemical and fuels has found its place among scientists in the past decade as a promising field to invest in for moving towards a greener future. However, finding catalysts for CO2R has been a real challenge for researchers. The four main requirements for a good CO2R catalyst performance include activity, selectivity, stability, and low cost. Furthermore, as catalysis is a surface based process, achieving high catalytically active surface areas exposed to CO2 while the conversion process is occurring is important.
The type of transition metal catalyst and the exposed surface facets used for CO2 reduction plays a role on the activity and selectivity towards different reaction products. Furthermore, tuning the 3-dimensional structure of CO2R electrodes enables control of the local reaction environment that can impact overall catalytic performance.1 In this work, we control the 3-dimensional structure of an Au catalyst coated on a polymeric-based substrate, along with investigating the impact of surface decoration of metal adatoms.
The coating of Au on the polymer substrate was accomplished following a previously developed electroless deposition method.2 CO2R was carried out in a custom designed three electrode cell reported previously3 with a flow of CO2 maintained over a 1 h chronoamperometry electrolysis process. The counter electrode was Pt foil and 0.1 M KHCO3 was used as the electrolyte.
The modified surface showed an almost 5 times higher peak in its cyclic voltammetry (CV) in compare to the plain surface. This means that the actual active surface area of the modified surface sample is almost 5 times higher the plain sample (demonstrated in Figure 1a). This significantly affects the CO2R performance of these surfaces. Figure 1b depicts the activity of the modified three-dimensional electrode surface and the two-dimensional plain surface as a function of electrode potential. By decorating these electrodes with other metal species at the surface we observed interesting activity and selectivity trends that arise due to synergistic interactions between the two metal species and modified transport properties due to the three-dimensionality of the polymer supported electrodes. In this presentation we will discuss these reactivity trends and provide insight into the activity and selectivity observed, supported by detailed structural analyses and supplementary measurements.

Figure 1. (a) CV of a plain and modified surface of Au in 2.25 M of H2SO4; the counter electrode was Pt foil and the scan rate was 50 mV/s. (b) Activity (current density vs. different electrode potentials) of both the three-dimensional modified and two-dimensional plain surfaces.

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Figure 1