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AN-EC-025

2021-07

Study of the hydrogen region at platinum electrodes with linear scan cyclic voltammetry

How VIONIC powered by INTELLO can be used to characterize processes at the Pt-electrolyte interface


Summary

The study of the electrochemical behavior of platinum in acidic media is of crucial importance in fundamental electrochemistry and electrocatalysis. Most electrocatalytic processes occurring at Pt electrodes are highly sensitive to the structure of the platinum surface.

Cyclic voltammetry (CV) is a widely used rapid measurement technique that provides both a qualitative and quantitative fingerprint of platinum surfaces. A comparison of results given by linear and staircase CVs is presented in this Application Note.


Experimental setup

VIONIC powered by INTELLO
Figure 1. VIONIC powered by INTELLO

The laboratory experiments in this study were performed with VIONIC powered by INTELLO from Metrohm Autolab (Figure 1).

As standard, VIONIC is equipped with a linear scan generator, allowing the possibility for users to perform linear sweeps and linear cyclic voltammetries on various samples. A Metrohm Pt wire was used as the working electrode (WE), and the counter electrode (CE) was the platinum sheet electrode. The Ag/AgCl 3 mol/L KCl electrode was used as a reference (RE).

For the electrochemical cell, an Autolab Electrocatalysis RRDE cell was employed and placed inside of a Metrohm Faraday cage.

Prior to the experiment, the glassware, electrodes, and the Teflon portion of the cell in direct contact with the electrolyte were cleaned with aggressive oxidizing solutions. A more detailed description of the cleaning protocol can be provided upon request.

An aqueous solution of sulfuric acid (0.5 mol/L H2SO4) was used as the electrolyte in this application.

Ultrapure water was used to prepare the cleaning and rinsing solutions as well as the electrolyte. The electrolyte was purged with argon gas for an hour before beginning the experiment.

The INTELLO procedure to characterize the platinum electrode surface consisted of a linear CV followed by a staircase CV. Each CV measurement began with polarizing the working electrode to 0.15 V. After a stabilization period of 3 s, the linear and staircase CV measurements followed. Each CV consisted of three scans, starting at 0.15 V, scanning up to the first vertex at 1.35 V, then scanning down to the second vertex at -0.21 V, and ultimately ending up at 0.15 V. 


Results and discussion

In Figure 3, the linear cyclic voltammograms performed at different scan rates and step potentials www.metrohm.com/electrochemistry 3 are shown. Each color corresponds to a cycle at a different scan rate, which is explained in Table 1.

A constant sampling interval of 10 ms was kept for all measurements.

The linear CV performed on the platinum electrode in sulfuric acid. For the color codes, refer to Table 1.
Figure 3. The linear CV performed on the platinum electrode in sulfuric acid. For the color codes, refer to Table 1.

Conclusion

In this Application Note, a comparison between linear and staircase cyclic voltammetry on a Pt electrode in sulfuric acid is given.

A visual observation of the cyclic voltammograms shows the necessity of linear CV using a linear scan in order to obtain a reliable fingerprint of the hydrogen region on platinum electrodes.

The same conclusion is also valid for many other fast electron transfers happening at catalysts immobilized at the surface of an electrode.


For more information

More information about this Application Note and the associated INTELLO software procedure is available from your local Metrohm distributor. Additional instrument specification information can be found here:

VIONIC powered by INTELLO

Author

Metrohm USA

9250 Camden Field Pkwy
33578 Riverview, FL

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