Fast-Response Operando Mass Spectrometry Demystifies C₂ Product Formation in Cu-Catalyzed CO and CO₂ Reduction: Burst of Ethylene Isotopologues
4 affiliations
- 1Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, United States, 94720
- 2Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, United States, 94720
- 3Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, United States, 94720
- 4Department of Materials Science and Engineering, University of California, Berkeley, 210 Hearst Memorial Mining Building, Berkeley, CA, United States, 94720
Abstract
It has been a long-standing challenge in electrocatalysis to measure product formation with kinetically relevant time resolution. Here, we couple a real-time gas analyzer mass spectrometer with a modified sampling inlet to a gas diffusion electrode cell, achieving sub-second time resolution for both reactant consumption and product formation. We focus on CO 2 /CO reduction on oxide-derived Cu, motivated by the continuing interest in its reaction mechanism and its high selectivity to ethylene (C 2 H 4 ) formation. Potential step experiments for CO reduction reveal that the initial consumption of CO is fast (< 1 s), but the appearance of C 2 H 4 products can be 10 times slower, which we attribute to the time required for CO storage on the Cu surface and subsequent reconstruction into the active, C 2+ -forming, configuration. Previous studies have reported that the co-feed of 12 CO 2 / 13 CO results in the enhancement of 13 C-containing ethylene isotopologues, but the mechanism causing this remains unknown. Isotopic-labeled gas switching ( 12 CO 2 - 13 CO) experiments yield compelling evidence that 13 C species continue to exist for more than a minute at near proximity to or on the catalyst, even after the supply source has been cut off, evidenced by the significant enhancement of 13 C-containing ethylene isotopologues: pure ( 13 C 2 H 4 ) and mixed ( 13 C 12 CH 4 ), formed through a CO 2 (g)-*CO pathway. Importantly, the size of the C 1 reservoir, the amount of 13 C 12 CH 4 made when CO 2 reacts with it, and the amount of Cu + that is removed are all in the micromole range. Thus, the picture emerges that a monolayer is stripped off from the copper catalyst surface during the CO-CO 2 switch. Tracking of dynamic Cu surface insights (i.e., activation, dissolution and deactivation) provides valuable mechanistic insights for optimizing reaction conditions.
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BibTeX
@misc{zeng2026fastresponse,
title = {{Fast-Response Operando Mass Spectrometry Demystifies C₂ Product Formation in Cu-Catalyzed CO and CO₂ Reduction: Burst of Ethylene Isotopologues}},
author = {Helen J. Zeng and Yesol Kim and Junko Yano and Joel W. Ager},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008486/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008486/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Fast-Response Operando Mass Spectrometry Demystifies C₂ Product Formation in Cu-Catalyzed CO and CO₂ Reduction: Burst of Ethylene Isotopologues
AU - Helen J. Zeng
AU - Yesol Kim
AU - Junko Yano
AU - Joel W. Ager
PY - 2026
DA - 2026/09/08
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008486/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008486/v1
AB - It has been a long-standing challenge in electrocatalysis to measure product formation with kinetically relevant time resolution. Here, we couple a real-time gas analyzer mass spectrometer with a modified sampling inlet to a gas diffusion electrode cell, achieving sub-second time resolution for both reactant consumption and product formation. We focus on CO 2 /CO reduction on oxide-derived Cu, motivated by the continuing interest in its reaction mechanism and its high selectivity to ethylene (C 2 H 4 ) formation. Potential step experiments for CO reduction reveal that the initial consumption of CO is fast (< 1 s), but the appearance of C 2 H 4 products can be 10 times slower, which we attribute to the time required for CO storage on the Cu surface and subsequent reconstruction into the active, C 2+ -forming, configuration. Previous studies have reported that the co-feed of 12 CO 2 / 13 CO results in the enhancement of 13 C-containing ethylene isotopologues, but the mechanism causing this remains unknown. Isotopic-labeled gas switching ( 12 CO 2 - 13 CO) experiments yield compelling evidence that 13 C species continue to exist for more than a minute at near proximity to or on the catalyst, even after the supply source has been cut off, evidenced by the significant enhancement of 13 C-containing ethylene isotopologues: pure ( 13 C 2 H 4 ) and mixed ( 13 C 12 CH 4 ), formed through a CO 2 (g)-*CO pathway. Importantly, the size of the C 1 reservoir, the amount of 13 C 12 CH 4 made when CO 2 reacts with it, and the amount of Cu + that is removed are all in the micromole range. Thus, the picture emerges that a monolayer is stripped off from the copper catalyst surface during the CO-CO 2 switch. Tracking of dynamic Cu surface insights (i.e., activation, dissolution and deactivation) provides valuable mechanistic insights for optimizing reaction conditions.
ER -