An Online Gas Chromatography Cell Setup for Accurate CO2-Electroreduction Product Quantification

Justus S Diercks,Antoine Faisnel,Piyush Chauhan,Thomas J Schmidt,Juan Herranz,Bernhard Pribyl-Kranewitter

doi:10.1149/1945-7111/ac0363

Justus S Diercks, Antoine Faisnel + Show 4 more

Open Access

https://doi.org/10.1149/1945-7111/ac0363

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Abstract

The electrochemical reduction of carbon dioxide (CO2) constitutes an increasingly important scientific topic and research on novel electrocatalysts for this demanding reaction is constantly increasing. One of the most important properties to be inferred for such electrocatalysts is their product selectivity and potential dependence thereof. However, the wide range of materials currently employed in CO2 electroreduction (e.g., Ag, Cu, Pd) entails a large variety of gaseous and/or liquid reaction products for which accurate quantification implies a major challenge. With this motivation, in this study we present an online gas chromatography cell setup specifically designed for the accurate and reproducible determination of the product selectivities of CO2-reduction electrocatalysts. Therewith, we assess the parameters influencing the cell’s performance and point out important design features, such as reproducible electrode alignment, minimized contact resistances and a low ratio among electrolyte volume and the electrodes’ geometrical surface area. The setup was validated by performing measurements on a Pt nanoparticle catalyst for which H2 is the only expected reduction product, while a Pd nanoparticle catalyst was subsequently used to verify its capabilities for CO2 electroreduction selectivity measurements involving multiple liquid and gaseous products.

Highlights

Whilefluidic reactors[28,29] and co-electrolyzer cells[17,30] implementing gaseous reactants in combination with gas diffusion electrodes and polymer electrolytes are becoming increasingly popular in the field of CO2RR, the complex interplay of the variables that define these devices’ performance renders them ill-suited for evaluating CO2-electroreduction catalysts
The unsaturated electrolyte features a significant reduction current over the first 100 s of the potentiostatic hold and fails to reach the saturation level of the pre-saturated electrolyte. Under such potentiostatic conditions and potential of choice, this measured current on such a Pt/C electrode can be ascribed to the reduction of residual O2 dissolved in the electrolyte, which should lead to products (H2O and/or H2O2) that are not detected by a CO2RR setup
This shall in terms lead to an underestimation of the corresponding Faradaic efficiency values that may be negligible over long potential holds at large currents and corresponding overpotentials, but which becomes a significant source of error in short potentiostatic holds at low current densities and overpotentials

Summary

Introduction

While (micro)fluidic reactors[28,29] and co-electrolyzer cells[17,30] implementing gaseous reactants in combination with gas diffusion electrodes and polymer electrolytes are becoming increasingly popular in the field of CO2RR, the complex interplay of the variables that define these devices’ performance renders them ill-suited for evaluating CO2-electroreduction catalysts. We started the assessment of this electrochemical utilization by performing cyclic voltammetry measurements on the electrochemically conditioned Pt/C and Pd/C working electrodes used hereafter both in the online GC cell and in RDE, using the catalyst loadings implemented in the former configuration (i.e., 25 vs 100 μgmetal·cm−2 for Pt/C vs Pd/C, respectively).

Results

Conclusion