Alternative technique for determining the true activity of catalysts
Researchers from Japan perform reliable estimation of the activity of water-splitting catalysts with an unconventional technique

Date:
January 31, 2022
Source:
Waseda University
Summary:
Electrolysis of water into hydrogen and oxygen is a potential source
of clean hydrogen fuel. However, the process requires efficient
electrocatalysts. Unfortunately, conventional techniques often
overestimate their efficiency. Now, researchers demonstrate
an alternative technique for gauging the electrocatalytic
performance accurately, opening doors to a smooth transition
from lab-scale studies to large-scale hydrogen fuel generation and
commercialization of new catalysts with no activity loss issues from
overestimation of activity with transient voltammetry techniques.



FULL STORY ========================================================================== Electrolysis of water or "water electrosplitting" has received a great
deal of attention recently owing to its potential as a clean source of hydrogen, the oft-touted fuel of the future. However, two issues have
long stood in the way: the large amount of energy lost, and the cost
of electrocatalysts (catalysts used for electrolysis). Fortunately,
several new kinds of electrocatalysts have made their appearance, which
could potentially solve these issues.


==========================================================================
The screening of new electrocatalysts is conventionally performed
with techniques such as "linear sweep voltammetry" (LSV) and "cyclic voltammetry" (CV), which involve applying a constantly changing voltage
to an electrode and monitoring the resulting current. As this current
depends on the rate of oxidation or reduction occurring at the electrode,
the measured current readings can be used to determine the effect of an electrocatalyst on the speed of the electrolysis reaction.

However, an obvious drawback of these techniques is that they cannot
accurately record the "steady-state" response of the electrocatalyst
as it does not experience a particular applied voltage long enough
to do so. As a result, substantially high current readings are often
recorded, which do not reflect the true catalytic activity, hindering
the development of efficient electrocatalysts and promotion of the same
to large-scale processes.

In a new study published in the Journal of The Electrochemical Society, Assistant Professor Sengeni Anantharaj from Waseda University, Japan,
along with his collaborators Dr. Subrata Kundu from CSIR-Central Electrochemical Research Institute, India, and Prof. Suguru Noda from
Waseda University have now found a way around this problem, demonstrating
an alternate technique called "sampled current voltammetry" (SCV) as a
more reliable indicator of electrocatalytic performance at a constant steady-state applied voltage.

"Screening catalysts accurately is just as important as developing new catalysts for all energy conversion reactions," says Anantharaj, speaking
of his motivation. "Our work has highlighted a way to make accurate measurements of electrocatalytic activity previously not possible with conventional transient techniques." Before applying the SCV technique,
the researchers analyzed the errors resulting from LSV. To show the
deviation in current values, they used a steady-state technique called "chronoamperometry" (CA), which is the most accurate method of all yet
time consuming to measure current at constant voltages and compared it
to the values obtained from LSV.

To determine the activity of electrocatalysts used in electrolysis, they measured the current readings of both the oxygen-producing and hydrogen- producing half-cell reactions. Using a stainless-steel (SS) electrode, precipitated Co(OH)2 (cobalt hydroxide), and platinum foil as catalysts
in a KOH (potassium hydroxide) solution, the researchers found that
the current density readings from LSV and CA differed significantly,
with the difference growing wider at higher applied voltages.

Using the same setup, they then applied the SCV technique and recorded the current densities at various fixed voltages obtained from the steady-state
CA responses. "To validate the suitability of SCV, we recorded the CA
responses of the SS electrode at various regularly increasing voltages
for 130 seconds, within which the SS interface was able to reach a steady state,"elaborates Anantharaj.

From the sampled current readings, the researchers found negligible
difference compared to the steady-state CA technique, demonstrating
the reliability of the SCV in correctly determining electrocatalyst's
behavior at different voltages.

Additionally, while the SCV is particularly useful in the search for a
suitable electrocatalyst for water electrosplitting, it can be used to
screen electrocatalysts accurately for any electrochemical reaction.

"By addressing the long-standing problem of catalyst performance loss
when promoted from the lab to the practical processes, our work could
speed up the worldwide adoption of large-scale hydrogen generation from electrolysis," comments Anantharaj.

========================================================================== Story Source: Materials provided by Waseda_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Sengeni Anantharaj, Subrata Kundu, Suguru Noda. Worrisome
Exaggeration of
Activity of Electrocatalysts Destined for Steady-State
Water Electrolysis by Polarization Curves from Transient
Techniques. Journal of The Electrochemical Society, 2022; 169 (1):
014508 DOI: 10.1149/1945-7111/ ac47ec ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220131083851.htm

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