Collectively, this work reveals the immense importance of invoking a true multi-scale picture of catalysis when modeling, because mesoscale mass transfer, nanoscale double layer structure, and molecular energetics all interplay non-intuitively and have critical effects that dictate observed rates!
Finally, we extend the model to explore how it can explain enhancements in CO2R observed upon the use of an inert salt that suppresses dielectric constant. This is a first step into understanding the role of non-standard solvent environments in CO2R and their effects on catalysis.
This shows that the terms that we so-often like to neglect as chemical engineers become really important in the concentrated environment of the electrical double layer, which is the environment in which electrocatalysis occurs!
Sensitivity analysis on the model reveals the importance of the solvent permittivity, the role of mass transfer, and the importance of each of the non-ideal terms in the excess chemical potential in enabling accurate prediction of rates.
The reduced reorganization energy increases the rate of CO2R as predicted by a Marcus-Hush-Chidsey framework for electron-transfer-limited coupled-ion-electron-transfer employed in our continuum model.
This allows us to really get to the heart of how the double layer structure controls rates in CO2R. Smaller hydrated cations pack more tightly in the EDL, which increases local electric fields, lowering dielectric permittivity, and correspondingly reducing the solvent reorganization energy.
The model employs zero adjustable parameters, and faithfully and quantitatively predicts the rate of CO2RR as a function of cation, electrolyte strength, and CO2 activity, as well as the local pH and CO2 activity measured by ATR-SEIRAS!
We also find that having an accurate double layer structure in the simulation allows us to get very accurate predictions of catalytic rates in our continuum model.
In this work, we develop a multi-scale model of the electrical double layer in CO2 reduction. By including a variety of non-ideal ion-specific effects, such as cation hydrolysis, steric excess potentials, and more, we can accurately the structure of the double layer as confirmed by impedance.
Super excited to share @Alex_James_King and my work on elucidating the role of the double layer in electrochemical CO2 reduction! This work has been years in the making, and excitingly, starts to get to the heart of how cations control rates of CO2R!
pubs.acs.org/doi/full/10....
Thank you Nathan!!
Thank you Jordi!!
Thank you Kelsey!!
Incredibly honored to be a member of this year’s Schmidt Science Fellows Cohort! I am very excited to leverage this unprecedented opportunity to pivot into AI and automation to build autonomous flow reactors for optimizing electro organic synthesis. #chemsky 🧪 #compchemsky
Oral and poster sessions for Engineering CO2 Reduction environments
I am co-chairing a session for @acs.org Fall 2024 on engineering systems and microenvironments for electrochemical CO2 reduction. We think it'll be a great session and encourage anyone interested to submit abstracts! Due date is March 31! #Science #ChemSky #CompChemSky
Our article with @interphases.org on the role of ion management in enhancing performance for bipolar membranes in forward bias is now #OpenAccess as a part of @natchemeng.bsky.social’s @natureportfolio.bsky.social Anniversary issue! 🧪
Link: www.nature.com/articles/s44...
#ChemSky #CompChemSky
Check out this lovely summary of our recent @natchemeng.bsky.social paper by Jovan Kamcev and co-workers! Great for anyone looking for an abridged version of the original work! 🧪
#GreenSky #ChemSky #CompChemSky
www.nature.com/articles/s44...
Thanks!!
Sharing our recent work on continuum modeling of forward bias bipolar membranes for more visibility with #ChemSky and #CompChemSky! As always I am happy to answer any questions about this work! 🧪
Finally, thanks to @ucberkeleyofficial.bsky.social and @berkeleylab.bsky.social for being such a great home to work on BPM research for the last 5 years. Super proud of all that we were able to do together on this topic, and looking forward to watching this space in the future! (11/11)
I also want to give a special shoutout to my former undergraduate mentee, Andrew Liu who performed many of the initial simulations that provided the groundwork for the findings in this work. (10/11)
This work was a massive team effort and could not have been done without my exceptional collaborators, Eric Lees, James Toh, Nathan Stovall, Priyamvada Goyal, and Kiko Galang, along with the support of our PIs, Adam Weber, Alexis Bell, and Yogi Surendranath. (9/11)
Finally, we highlight potential routes to alleviate these challenges, identifying that rational materials design of BPMs with high concentrations of selective fixed-charge will be pivotal to enabling these future technologies! (8/11)
Influence of carbon dioxide absorption on limiting current density in forward-biased bipolar membranes.
For this reason, CO2 absorption into the AEL as carbonates is an existential challenge for FB-BPMs, because divalent carbonate anions thoroughly outcompete OH- for recombination sites at the interface. (7/11)
Multi-component phenomena complicate matters further by reducing the number of available sites for recombination, highlighting the importance of designing membranes selective to H+ or OH-, whose recombination reaction represents the highest achievable current and voltage. (6/11)
Process of limiting current density in forward-biased bipolar membranes.
Second, mismatch between the counter-ion fluxes induces observed limiting current densities in forward bias, because when one ion becomes limiting relative to the other, the species in excess will cross-over through the junction and attenuate the achievable voltage. (5/11)
Figure showing the role of conjugate acid pKa on the open circuit potential of a bipolar membrane.
First, the pKa of the recombination product formed at the AEL|CEL interface and the valency of the recombining ion dictate the open circuit potential of the system, because the OCP is achieved at the point where counter-ion recombination and co-ion crossover are balanced. (4/11)
We sought to understand these limitations through continuum modeling of the multi-component transport and reaction kinetics occurring in these systems. Ultimately, we reveal some interesting and non-intuitive phenomena that limit the performance of FB-BPMs. (3/11)
Applications of forward-biased bipolar membranes.
There are many applications where forward-biased BPMs can be useful, from self-humidifying hydrogen fuel cells, to lower voltage electrolyzers, and even to acid-base recombination batteries. However, these systems have long been limited in the rates that they can achieve. (2/11)