Energy
Energy conversion, Carbon-neutral, Green transformation

Multiscale design of CO2 electrolysis systems
Research Center for Solar Energy Chemistry, Graduate School of 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 1.7 A/cm2. The faradaic efficiency
for multicarbon products increased with the current density andreached 76% at a total current density of 1.6 A/cm2. Optimizing thestandard components and their assembly as the cathode elicits
the high-turnover frequency of Cu catalysts, resulting in the record
partial current density for C2+.

▍ Significance of the research and Future perspective
It is noteworthy that this electrode allowed us to achieve ultrahigh-rate CO2 electrolysis even in neutral solutions, which is morepractical than alkaline solutions. In addition, the present study succeeded in eliciting the potential performance of an ordinary combination. The design guidelines obtained from the ultra-high-rate CO2
electrolyisis with only ordinary materials would be quite general,and thus, they are expected to be widely applicable to novel materials and systems.

Energy▍ Background & Results
Electrochemical CO2 reduction reaction (CO2RR) has attracted
considerable attention as a promising strategy for the valorizationof anthropogenic CO2. The increase in partial current density forsynthesizing C2+, such as ethylene and ethanol, is crucial for thesocial-implementation potential. Recently, the direct electroreduction of gaseous CO2 using gas diffusion electrode (GDE) has been
widely studied because it can overcome the problem of masstransport limitation due to the low solubility of CO2. However, thepartial current density for C2+ has remained below 800 mA/cm2
even when using GDEs in most previous studies.
The present work attempts to pursue a high partial current density for C2+ (jC2+) using neutral electrolytes by optimizing the standard
components and properly assembling them as the cathode. In particular, we achieved a record current density of 1.7 A/cm2 for multicarbon products in neutral electrolytes using synthetic or commercial Cu nanoparticles and carbon-based gas diffusion layers. The
faradaic efficiency for C2+ increased with increasing current density
in the present ultra-high-rate CO2 electrolysis system, and thus, a
trade-on relationship between rate and selectivity was exhibited.
Although there are many requirements to obtain ultra-high-rateelectrolysis, including the nature and size of catalysts, and the porosity of catalytic layers, we demonstrated that the thickness of catalyst layers was one high-sensitive factor in determining maximumcurrent density for C2+. We believe that this study suggests a novel
approach to enlarging the triple-phase interface for enhancing theperformance of electrocatalysis processes involving gases.

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. 2022 in press, doi: 10.1039/D2EY00035K
Tr e a t i s eLiu, Tengyi; Nakanishi, Shuji; Kamiya, Kazuhide et al. A Tin Oxide-Coated Copper Foam Hybridized with a Gas Diffusion Electrode for Efficient
CO2 Reduction to Formate with a Current Density Exceeding 1 A cm−2. Small. 2022 in press, doi: 10.1002/smll.202205323
UR
L https://rcsec.osaka-u.ac.jp/nakanishilab
K e y w o r d chemical valorization of CO2, electrocatalysts, multi-scale simulation, artificial photosynthesis