
Cyclic voltammetry (CV) – the essential analytical technique for catalyst research

In the last decade, a greater understanding of critical electrochemical transformations has been established, particularly those that involve water, hydrogen, and oxygen [1]. The expansion of our understanding in this realm was only possible because of the use of critical electrochemical techniques. This has allowed researchers to not only explore a wider variety of catalysts, but explore them in greater detail.
To respond to the potential volume of exploration which may discover more cost-effective and renewable materials that are not at the stage of critical depletion, a systematic approach to analytical research is required.


Instrumentation for CV analysis of catalysts from Metrohm Autolab.
Experimental Goals and Procedure Selection
Exploring a new system
Determine the (E) stability window of the electrolyte [2]
Method: Perform CV measurement in broad voltage (E) window, using an inert electrode (e.g. glassy carbon) and investigate the general redox behavior of the electrocatalyst material.
Investigate the general redox behavior of the electrocatalyst material [2]
Method: Perform CV measurement in a broad voltage (E) window, using a well understood electrolyte and new electrocatalyst.
Determine the electrode surface area for quantitative comparisons [3–5]
Method: Various methods that are material dependent: using a well-defined surface reaction (e.g. stripping or oxide formation) or analysis of electrochemical double layer capacitance (Cdl).
Investigate the stability of the electrocatalyst [6, 7]
Method: Perform repetitive CV measurements over several hundred cycles or during several days.
Probing a specific electrochemical reaction
Determine if a reaction is reversible (fast electron transfer kinetics), quasi reversible (slow kinetics), or irreversible (governed by other factors) [8, 9]
Method: Perform CV measurements at various scan rate values, then examine dependencies for the peak position (Epeak) and peak height (Ipeak) on the scan rate.
Determine the apparent activation energy of the reaction [10]
Method: Perform CV measurements at various temperatures, then analyze electrochemical Arrhenius plots of log j vs. 1/T.
Combining CV with additional techniques to confirm results and deepen understanding
Determine the molecular structure of products or intermediates at a specific instance of the reaction [9–12]
Method: Perform CV measurement with in-situ spectroscopic determination (spectroelectrochemistry via UV/Vis/NIR or Raman spectroscopy).
Investigate material deposited or removed from the electrode surface during the electrochemical measurement [13]
Method: Measure the mass change at the electrode surface during a CV measurement using electrochemical quartz crystal microbalance (EQCM).
From action to reactions in the literature

Focal parameters for exploration:
1. Catalyst Microstructure
Research goal: Determine the electrode surface
Using microscope images combined with the Cdl (double layer capacitance) and ionomer coverage, the researchers were able to analyze and quantify their catalyst layer. They used CV to determine ionomer coverage over the carbon by comparing Cdl values (wet versus dry).
2. Transport Properties
Research goal: Investigate material deposited or removed from the electrode surface during the electrochemical measurement
Additional research investigating the electrode surface was performed with CV. Using a rotating disk electrode, the researchers were able to determine the gas transport resistance by measuring the ORR (oxygen reduction reaction). CV also allowed the determination of the Pt roughness factor.
3. I-V performance
Research goal: Use CV I-V to calculate the fuel cell performance
I-V performance is a typical measurement for the overall performance of the fuel cell. A potentiostat is needed to measure the actual I-V curve in order to determine the Pt loading so that the I-V performance can be interpreted and compared among various samples.
Your initial investigations with CV may not provide all of the answers at first glance, but you can then move on to more complex setups and experiments with complete insight.
Curious about electrochemistry?
[1] Seh Z. W.; Kibsgaard J.; Dickens C. F.; et al. Combining Theory and Experiment in Electrocatalysis: Insights into Materials Design. Science 2017, 355, 6321. doi:10.1126/science.aad4998
[2] Kübler, P.; Sundermeyer, J. Ferrocenyl-Phosphonium Ionic Liquids – Synthesis, Characterisation and Electrochemistry. Dalton Trans. 2014, 43 (9), 3750–3766. doi:10.1039/C3DT53402B
[3] Biegler, T.; Rand, D. A. J.; Woods, R. Limiting Oxygen Coverage on Platinized Platinum; Relevance to Determination of Real Platinum Area by Hydrogen Adsorption. J. Electroanal. Chem. Interfacial Electrochem. 1971, 29 (2), 269–277. doi:10.1016/S0022-0728(71)80089-X
[4] Trasatti, S.; Petrii, O. A. Real Surface Area Measurements. Int. Union Pure Appl. Chem. 1991, 63 (5), 711–734. doi:10.1351/pac199163050711
[5] Kinkead, B.; van Drunen, J.; Paul, M. T. Y.; et al. Platinum Ordered Porous Electrodes: Developing a Platform for Fundamental Electrochemical Characterization. Electrocatalysis 2013, 4 (3), 179–186. doi:10.1007/s12678-013-0145-2
[6] Pilapil, B. K.; van Drunen, J.; Makonnen, Y.; et al. Ordered Porous Electrodes by Design: Toward Enhancing the Effective Utilization of Platinum in Electrocatalysis. Adv. Funct. Mater. 2017, 27 (36), 1703171. doi:10.1002/adfm.201703171
[7] Xing, L.; Hossain, M. A.; Tian, M.; et al. Platinum Electro-Dissolution in Acidic Media upon Potential Cycling. Electrocatalysis 2014, 5 (1), 96–112. doi:10.1007/s12678-013-0167-9
[8] Rountree, E. S.; McCarthy, B. D.; Eisenhart, T. T.; et al. Evaluation of Homogeneous Electrocatalysts by Cyclic Voltammetry. Inorg. Chem. 2014, 53 (19), 9983–10002. doi:10.1021/ic500658x
[9] Sokolov, S.; Sepunaru, L.; Compton, R. Taking Cues from Nature: Hemoglobin Catalysed Oxygen Reduction. Appl. Mater. Today 2017, 7, 82–90. doi:10.1016/j.apmt.2017.01.005
[10] Barbosa, A. F. B.; Oliveira, V. L.; van Drunen, J.; et al. Ethanol Electro-Oxidation Reaction Using a Polycrystalline Nickel Electrode in Alkaline Media: Temperature Influence and Reaction Mechanism. J. Electroanal. Chem. 2015, 746, 31–38. doi:10.1016/j.jelechem.2015.03.024
[11] Hernández, C. L.; González GarcÃa M. B.; Santos , D. H.; et al. Aqueous UV-VIS Spectroelectrochemical Study of the Voltammetric Reduction of Graphene Oxide on Screen Printed Carbon Electrodes. doi:10.1016/j.elecom.2016.01.017
[12] Görlin, M.; de Araújo, J. F.; Schmies, H.; et al. Tracking Catalyst Redox States and Reaction Dynamics in Ni-Fe Oxyhydroxide Oxygen Evolution Reaction Electrocatalysts: The Role of Catalyst Support and Electrolyte PH. J Am Chem Soc 2017, 139 (5), 2070–2082. doi:10.1021/jacs.6b12250
[13] Lee, C-L.; Huang, K-L.; Tsai, Y-L.; et al. A Comparison of Alloyed and Dealloyed Silver/Palladium/Platinum Nanoframes as Electrocatalysts in Oxygen Reduction Reaction. Electrochem. Commun. 2013, 280–285. doi:10.1016/j.elecom.2013.07.020
[14] Vos, J. G.; Koper, M. T. M. Measurement of Competition between Oxygen Evolution and Chlorine Evolution Using Rotating Ring-Disk Electrode Voltammetry. J. Electroanal. Chem. 2018, 819, 260–268. doi:10.1016/j.jelechem.2017.10.058
[15] Kocha, S. S.; Shinozaki, K.; Zack, J. W.; et al. Best Practices and Testing Protocols for Benchmarking ORR Activities of Fuel Cell Electrocatalysts Using Rotating Disk Electrode. Electrocatalysis 2017, 8 (4), 366–374. doi:10.1007/s12678-017-0378-6