Energy
Energy conversion, Carbon-neutral, Green transformation

Multiscale design of high-rate CO2 electrolysis systems
Research Center for Solar Energy Chemistry, Graduate School of Engineering Science
Associate Professor Kazuhide Kamiya
https://researchmap.jp/kamiya0908?lang=en

Abstract
We have successfully increased the partial current density forelectrochemical CO2 reduction reactions to multicarbon products(C2+) over Cu nanoparticles on gas diffusion electrodes in neutralelectrolytes to a record value of 1.8 A/cm2. Furthermore, a hybridgas diffusion electrode coated with tin oxide on metal foam wasdeveloped, achieving efficient CO2 reduction to formate with a current density surpassing 1 A/cm2.

Energy▍ Background & Results
The electrochemical CO2 reduction reaction (CO2RR) is a promising strategy for closing the carbon cycle. Increasing the current
density (J) for CO2RR products is a critical requirement for the social implementation of this technology. There are many factors withdifferent size scales, such as catalysts, electrodes, and electrolysis
cells, that determine the activity of CO2 electrolysis. However, manystudies have focused only on single elements, with little researchon how to harmonize their functions as a whole. Based on our philosophy of appropriately selecting and arranging these elements
to function in harmony and maximize the potential of each material,
we carried out research and successfully achieved high reaction
rates for CO2RR.
Specifically, nanoscale tin-oxide-modified copper-oxide foam
was hybridized with a carbon-based gas-diffusion electrode (GDE).
Using the resultant electrode, we increased the Jformate to 1.1 A/cm2
at −1.2 V vs. RHE in 1 M KOH, which is the highest value for CO2to-formate electrolysis. In addition, we have successfully increased
the partial current density for gaseous CO2 reduction reactions tomulticarbon products (C2+) over Cu nanoparticles on gas diffusion
electrodes to a record value of 1.8 A/cm2 in KOH solutions.

▍ Significance of the research and Future perspective
Our work demonstrated the relevance of consistent design fromthe micro to the macro scale, and would be expected to become ageneral guideline for future energetic device studies. This can beseen as a fusion of research across different scales, and the principles and materials derived here are expected to be significantly
different from those derived from single-scale research. Additionally, as the current density for the production of high value-added
products is correlated with the capital cost of the employed electrodes, these ultra-high current electrolysis will become important
cornerstones for their social implementation.

Schematic illustration of gaseous CO2 electrolysis

Multiscale design of CO2 electrolysis systems

P a t e n t
Inoue, Asato; Nakanishi, Shuji; Kamiya, Kazuhide et al. Ultra-high-rate CO2 reduction reactions to multicarbon products with a current density of 1.7 A/cm2
in neutral electrolytes. EES Catalysis. 2023, 1, 9–16. doi: 10.1039/D2EY00035K
Liu, Tengyi; Nakanishi, Shuji; Kamiya, Kazuhide et al. A tin oxide-coated copper foam hybridized with a gas diffusion electrode for efficient CO2 reduction
Tr e a t i s eto formate with a Current density exceeding 1 A cm−2. Small. 2022, 18, 2205323. doi: 10.1002/smll.202205323
Kato, Shintaro; Nakanishi, Shuji; Kamiya, Kazuhide et al. Selective and high-rate CO2 electroreduction by metal-doped covalent triazine frameworks: A
computational and experimental hybrid approach. Chemical Science. 2023, 14, 613–620. doi: 10.1039/D2SC03754HURLK e y w o r d CO2 electrolysis, net zero emissions, multi-scale simulation, artificial photosynthesis