Key Takeaways & Executive Findings
- •• • Cu reconstruction in CO2RR requires Cu+ species generated from HCO3−-mediated ·OH radicals; in HCO3−-free acidified K2SO4 electrolyte, reconstruction is minimal, indicating that oxidative dissolution-redeposition dominates only under neutral/alkaline conditions. This dictates electrolyte selection for stable CO2RR operation. • • CORR-induced reconstruction proceeds independently of Cu+ and ·OH, with potential-induced atomic migration as the sole mechanism; this enables reconstruction even in HCO3−-free electrolytes, simplifying electrolyte management for CORR. • • DFT calculations show that adsorbed *CO weakens Cu–Cu bonds, creating metastable surface configurations that lower the activation barrier for atomic migration; this explains why CORR, which produces high *CO coverage, promotes migration-driven reconstruction. • • In situ AFM and DFT results across varying potentials confirm that applied potential promotes both mechanisms, with the balance shifting from dissolution-redeposition to atomic migration as potential increases; this provides a unified framework for predicting reconstruction under operational conditions.
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Abstract
Elucidating the fundamental mechanisms underlying Cu reconstruction is paramount for the rational design of catalysts that meet the stringent activity, selectivity, and durability requirements for industrial-scale CO2/CO electroreduction (CO2RR/CORR). While both dissolution-redeposition and atomic migration pathways have been proposed, the operational conditions dictating their relative dominance remain poorly understood. Through quasi in situ Cu+ detection and in situ atomic force microscopy (AFM), we reveal a striking mechanistic dichotomy: Cu reconstruction during CO2RR occurs strictly in the presence of Cu+, whereas CORR-induced reconstruction proceeds independently of Cu+ species. These findings suggest that Cu reconstruction in CO2RR follows a dissolution-redeposition mechanism induced by oxidative radicals, while atomic migration emerges as the dominant pathway in CORR. Density functional theory calculations further demonstrate that adsorbed *CO intermediates reduce Cu–Cu bond strength, creating metastable surface configurations that promote Cu atomic migration. The investigation extends to broader metal catalysts (e.g., Ag, Au, Zn) and highlights the interplay between adsorbed species, interfacial environments, and applied potentials. Our findings establish a unified framework for understanding Cu restructuring dynamics, providing a paradigm for strategically engineering metal catalysts through controlled reconstruction, advancing the rational design of CO2RR/CORR systems.
1. Introduction
Electrochemical CO2/CO reduction (CO2RR/CORR) offers a sustainable route to value-added multi-carbon products, but the inherent low cohesive energy of metallic Cu causes potential-driven migration and structural reconstruction under cathodic conditions. This dynamic reconstruction compromises meticulously engineered architectures—such as Cu(100) single crystals and faceted Cu nanocubes—leading to diminished selectivity toward multi-carbon products. While strategic electrolyte engineering can direct reconstruction toward favorable facets, the operational conditions that dictate whether reconstruction follows dissolution-redeposition or atomic migration remain poorly understood, hindering rational catalyst design.
Existing mechanistic studies propose two pathways: dissolution-redeposition mediated by oxidative hydroxyl radicals (·OH) from bicarbonate/H2O oxygen exchange, and potential-induced atomic migration driven by electric field effects. However, the relative dominance of these pathways under varying atmospheres and electrolyte compositions has not been resolved. This work addresses the bottleneck by combining quasi in situ Cu+ detection, in situ atomic force microscopy, and density functional theory to identify the specific conditions that trigger each mechanism. The findings establish a unified framework that links adsorbed species, interfacial environments, and applied potentials to Cu reconstruction dynamics, enabling strategic engineering of metal catalysts for industrial-scale CO2RR/CORR.
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YUE Yunpei, WU Zhitan, YE Zilin, LI Zhiguo, WANG Xinyu, XIE Kai, HAN Daliang, YANG Quan-Hong, WENG Zhe (2025). Identifying Cu reconstruction mechanism in CO2 and CO electroreduction via Cu+ detection and in situ atomic force microscopy. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3412-2
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Frequently Asked Questions
What is the primary failure mechanism that degrades Cu-based catalysts during CO2RR, and how does this work quantify it?
The primary failure mechanism is potential-driven Cu reconstruction, which compromises engineered architectures such as Cu(100) single crystals and faceted Cu nanocubes, leading to diminished selectivity toward multi-carbon products. This work quantifies reconstruction via quasi in situ Cu+ detection and in situ AFM, showing that in CO2RR, reconstruction strictly requires Cu+ species generated from HCO3−-mediated ·OH radicals. In HCO3−-free acidified K2SO4 electrolyte, reconstruction is minimal, indicating that eliminating HCO3− or ·OH suppresses the dissolution-redeposition pathway.
How does the reconstruction mechanism differ between CO2RR and CORR, and what are the operational implications?
In CO2RR, reconstruction follows a dissolution-redeposition mechanism dependent on Cu+ and ·OH, requiring neutral or alkaline electrolytes that promote ·OH formation via HCO3−. In CORR, reconstruction proceeds independently of Cu+ and ·OH, driven solely by potential-induced atomic migration. Operationally, this means CORR can use HCO3−-free electrolytes without suppressing reconstruction, whereas CO2RR requires careful electrolyte selection to control reconstruction. The coexistence of both mechanisms occurs when potential is sufficient for significant CO and local HCO3− generation.
What is the role of adsorbed *CO in Cu reconstruction, and how does it affect Cu–Cu bond strength?
DFT calculations demonstrate that adsorbed *CO intermediates reduce Cu–Cu bond strength, creating metastable surface configurations that promote Cu atomic migration. This weakening of Cu–Cu interactions lowers the barrier for atomic migration, making it the dominant pathway in CORR where *CO coverage is high. The effect is not limited to reaction intermediates; other adsorbable species such as electrolyte anions, cations, and additives can similarly influence M–M bonds, extending the principle to Ag, Au, and Zn catalysts.
What experimental evidence supports the conclusion that applied potential promotes both reconstruction mechanisms?
In situ AFM and DFT results across varying potentials provide evidence that applied potential promotes both dissolution-redeposition and atomic migration. The balance shifts with potential: at low overpotentials in CO2RR, limited CO production leads to predominant *CO2 adsorption, and reconstruction requires neutral or alkaline electrolytes for ·OH formation. At higher potentials, significant CO and local HCO3− generation lead to continuous ·OH production and *CO-induced Cu spacing enlargement, resulting in coexistence of both mechanisms. This unified framework is supported by the observed potential-dependent reconstruction dynamics.
Can the findings be generalized to other metal catalysts, and what are the scalability bottlenecks?
The principle that adsorbed intermediates elongate and weaken M–M bonds applies broadly to metal catalysts such as Ag, Au, and Zn used in CO2RR/CORR. The scope of adsorbable species extends beyond reaction intermediates to electrolyte anions, cations, and additives. Scalability bottlenecks include the need for in situ characterization techniques (AFM, Cu+ detection) that are not amenable to high-throughput industrial monitoring, and the challenge of maintaining controlled reconstruction across large electrode areas. However, the unified framework enables strategic engineering of metal catalysts through controlled reconstruction, potentially reducing reliance on precious metals and improving durability.
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