Electrochemistry Laboratory

Electrochemical setup for online FTIR and Differential Electrochemical Mass

Spectrometry studies of CO2-electroreduction on model metal surfaces Yohan Paratcha, Julien Durst, Juan Herranz, Thomas J. Schmidt

Electrochemistry Laboratory, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland

Carbon dioxide is a major contributor to global warming and, beyond the mandatory reduction of our emissions, the possibility of recycling this greenhouse gas is

becoming increasingly attractive. The electrochemical reduction of CO2 is an interesting pathway since a broad range of useful products can be formed such as

methanol and formic acid (fuels for PEFC), methane and ethylene (reactants for synthesis or combustion process), CO and H2 (syngas) etc. [1]. Nevertheless, on

top of the high overpotential required to drive this reaction, the electrochemical reduction of CO2 suffers from a poor yield/selectivity of valuable products [2, 3]. In

order to overcome these two barriers, a better fundamental understanding of this reaction is urgently needed. For this purpose, we have designed a Differential

Electrochemical Mass Spectrometry (DEMS) setup coupled with an electrochemical flow cell that allows the in-operando quantification of the volatile species

produced in the course of the reaction. The behavior of copper, gold and platinum single-/poly-crystalline electrodes toward the CO2 electrochemical reduction

will be studied in order to better understand the origin of the different selective formation of specific products on these materials.

Conclusions and outlooks

[1] Kuhl et al., Energy Environ. Sci., 2012, 5, 7050

[2] Watanabe et al., J. Electrochem. Soc., 1991, 138, 3382

[3] Hori et al., Electrochim. Acta, 1994, 39, 1833

[4] www.pineinst.com/echem/imagebrowser.asp?productID=46967&imageID=757

[5] Jusys et al., J. Electrochem. Soc., 1999, 146, 1093

The preliminary results of this work show the production and the detection of hydrocarbons from the electroreduction of CO2 with a DEMS setup. The results have

been obtained with a Cu polycrystalline electrode. Further studies will be done using different electrolytes , different pH conditions and single crystal electrodes.

Moreover, the setup is adapted to FTIR characterization and the technique will be used in a future work for the identification of adsorbed species on electrode

surface.

Improvements on both the flow cell and the three-electrode cell setups are ongoing to maximize the reliability of the results.

Preliminary results

Electrochemical measurements were done

using chronoamperometry coupled with

mass spectrometry.

Experimental conditions:

WE: Polycrystalline Cu disk

RE: Hg/HgSO4

CE: Pt-mesh

Electrolyte: CO2 sat. 0.1M KHCO3

Potential steps (a):

-starting at -0.51 V/RHE

-steps of -0.05V, holding potential for 5 min

-back to -0.51V/RHE for 5 min between

each step

Hydrogen evolution reaction clearly

identified (b)

Correlation between potential steps and

increase of methane signal (c)

CO2 signal decreases during potential

steps and increases during potential

rests (d)

Electrolyte flow path

Electrochemical

cell

Turbo molecular

pumps

Quadrupole Mass

Spectrometer

(QMS)

Aperture Ø 0.2 mm

Ch 1 Ch 2

Oil pump Membrane

pump

PTFE membrane

0.02 μm pore

DEMS Measurements can be done either with a standard three-electrode

electrochemical cell (not shown here) or a dual thin-layer flow cell.

1: PTFE Electrode holder (Fig. 1)

2: PEEK Upper compartment V= 24 μL

3: Upper PTFE gasket

4: PEEK Flow distributor (Fig. 2)

5: Lower PTFE gasket

6: PEEK Lower compartment V= 46 μL

7: PTFE Membrane seal

8:PTFE Membrane and frit support

9: SS Connector to vacuum system

Counter electrode (CE) on the inlet

Reference electrode (RE) on the outlet

Dual thin-layer flow cell design

3

1

2

4

5 6

7

8

9

In

Out

Custom-made DEMS setup

Figure 1: Electrode

holder with Pt disk [4]

Electrochemical cell

Figure 2: Vertical section of the flow distributor of the dual thin-

layer flow cell

Design adapted from Jusys et al. work [5]

A syringe pump injects the electrolyte through FEP tubes.

Common flow rate range: 0.5 – 1.5 mL/min

The tubes are plugged in the flow distributor (Fig. 2)

Electrolyte flows through upper and lower compartments via

capillaries

The volatile products cross through the porous membrane -> MS

(a)

(b)

(c)

(d)

P1=4x10-2 mbar P2=4x10-5 mbar

Acknowledgements

This work is supported by CCEM, CTI and the SCCER H&E storage.

We thank them for the financial support.

Thanks to catalysis and interfaces group of ECL PSI