In fluidized electrocatalysis, catalytic particles work in rotation and are only momentarily ‘electrified’ when they collide with the electrode, leading to improved fatigue-resistance. Image: Northwestern University.Researchers at Northwestern University have developed a more efficient and stable method for conducting electrocatalytic reactions, which they report in a paper in CCS Chemistry.
The method, which involves fluidizing catalyst particles in electrolyte instead of gluing them to electrodes, avoids a rapid decline in reaction performance – a phenomenon researchers call fatigue. This approach could improve production processes for electrolysis and electrochemical energy conversion and storage.
"There has been extensive effort to find new high-performance catalysts that can also better withstand electrochemical reactions," said Jiaxing Huang, professor of materials science and engineering at Northwestern University’s McCormick School of Engineering, who led the research. "We developed a drastically different approach to make electrocatalysis less prone to decay – not by finding another new material, but by doing the reaction differently."
In a typical electrocatalysis process, catalytic materials are glued onto the electrode and then soaked in electrolyte, before undergoing a reaction spurred by a voltage. Since the voltage is continuously applied through the electrode, the materials experience continuous electrochemical stress. Over time, their catalytic performance can decay due to accumulated structural damage in the electrode as a whole and the degradation of individual particles.
The team's approach avoids this continuous stress by fluidizing the particles in the electrolyte. Now the particles work in rotation, experiencing electrochemical stress only momentarily when colliding with the electrode. Collectively, the output from the individual collision events merge into a continuous and stable electrochemical current.
"Fluidized electrocatalysis breaks the spatial and temporal continuum of electrochemical reactions, making the catalysts more efficient," explained Huang. "Fluidization also reduces the mass transport limit of the reactants to the catalyst, since the particles are swimming in the electrolyte."
Huang tested his ideas on a well-known, commercially available catalyst called Pt/C. This is made of carbon black powders decorated with platinum nanoparticles, and catalyzes oxygen evolution, hydrogen evolution and methanol oxidation reactions. When catalyzed by Pt/C, these three electrochemical reactions normally suffer from severe performance decay, but all showed higher efficiency and stability when the particles were fluidized.
"The new strategy makes an unstable catalyst deliver stable performance for all three of the model reactions. It was an exciting proof-of-concept," said Yi-Ge Zhou, the first author of the paper and a former visiting postdoc in Huang's group. "When we calculated single particle efficiency for some of these reactions, it was at least three orders of magnitude higher than the fixed particles. Instead of stressing them out, we gave the particles a chance to relax, and they became a lot more efficient as a result."
While more work is needed to identify the types of electrochemical reactions that could best benefit from fluidized electrocatalysis, Huang believes his method could be applied to a variety of different types of materials and produce more efficient, longer lasting electrocatalytic reactions. This could lead to improved electrochemical synthesis processes, which play an important role in converting energy to chemicals for large-scale energy storage.
"I hope other researchers consider our method to re-evaluate their catalysts. It would be exciting to see previously deemed unusable catalysts become usable," Huang said.
This story is adapted from material from Northwestern University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.