Key Takeaways & Executive Findings
- •• • CuCe10Ox delivers a CH4 Faradaic efficiency of 61.7% at -1.6 V vs. RHE, demonstrating that isolated Cu centers surrounded by Ce-Ov sites favor deep hydrogenation, a key metric for renewable methane production. • • Cu10CeOx achieves a C2 Faradaic efficiency of 61.5% at -1.4 V vs. RHE, showing that dense Cu sites enhance *CO coverage and C-C coupling, critical for producing multi-carbon fuels. • • The *CO stripping charge measurements confirm higher *CO coverage on Cu10CeOx than on CuCe10Ox, directly linking local active-site density to intermediate availability and product distribution. • • The molten salt-assisted synthesis enables precise tuning of Cu and Ce-Ov site concentrations, providing a scalable method to engineer catalyst selectivity for industrial CO2 valorization.
Abstract
The local concentration and configuration of active sites critically influence the selectivity of CO2 electroreduction, yet constructing well-defined structures to probe this relationship remains challenging. Here, we report a molten salt-assisted strategy to synthesize Ce-Ov-Cu cascade catalysts with tunable configurations and relative concentrations of Cu and Ce-Ov sites. Two distinct geometries were engineered: one with dense Cu sites surrounding Ce-Ov (Cu10CeOx) and another with isolated Cu centers encapsulated by Ce-Ov (CuCe10Ox). These configurations direct key intermediates (*CHO or *COH) toward either C-C coupling or deep hydrogenation, thereby switching product selectivity. CuCe10Ox achieves a CH4 Faradaic efficiency (FE) of 61.7% at -1.6 V vs. RHE, whereas Cu10CeOx favors C2 production with a maximum FE of 61.5% at -1.4 V vs. RHE. Mechanistic studies reveal that locally concentrated Cu sites exhibit strong *CO2 binding affinity, enhancing *CO surface coverage and facilitating *CO-*COH coupling. In contrast, Ce-Ov-rich regions with isolated copper centers supply abundant *H, promoting deep protonation of *CHO toward CH4. This work provides insights into catalyst design, demonstrating that manipulating structural chemistry can guide CO2RR toward targeted products.
1. Introduction
Global energy demand growth has intensified CO2 emissions, driving research into carbon capture and utilization. Electrochemical CO2 reduction (CO2RR) offers a route to convert renewable electricity into hydrocarbon fuels, but achieving high selectivity remains a bottleneck due to competing reaction pathways. Copper-based catalysts are unique in enabling C-C coupling, yet controlling whether intermediates undergo deep hydrogenation to CH4 or couple to form C2+ products is challenging. The local density and arrangement of active sites are hypothesized to govern intermediate coverage and reaction kinetics, but direct experimental evidence is scarce.
This study addresses the gap by synthesizing Ce-Ov-Cu catalysts with controlled active-site configurations. By varying the relative concentration of Cu and Ce-Ov sites, the authors create two distinct geometries: one with aggregated Cu sites and another with isolated Cu centers. These structures steer the reaction pathway, achieving high selectivity for either CH4 or C2 products. The work provides a clear demonstration that manipulating local active-site architecture can effectively direct CO2RR selectivity, offering a design principle for advanced electrocatalysts.
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Xiaoyue Zhu, Zijian Li, Yuhang Zhang, Yanru Geng, Min Gyu Kim, Haeseong Jang, Shangguo Liu, Xien Liu, Qing Qin (2026). Active Site Concentration Steers the Reaction Pathway of CO2 Electroreduction. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-4034-3
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Frequently Asked Questions
What is the mechanistic origin of the selectivity switch between CH4 and C2 products in the Ce-Ov-Cu catalysts?
The selectivity is governed by the local concentration of Cu and Ce-Ov sites. In Cu10CeOx, dense Cu sites enhance *CO2 binding and increase *CO coverage, promoting *CO-*COH coupling and C2 formation. In CuCe10Ox, abundant Ce-Ov sites facilitate water dissociation, supplying *H that drives deep hydrogenation of *CHO to CH4.
How do the Faradaic efficiencies of the catalysts compare at their optimal potentials?
CuCe10Ox achieves a CH4 FE of 61.7% at -1.6 V vs. RHE, while Cu10CeOx reaches a C2 FE of 61.5% at -1.4 V vs. RHE. These values indicate high selectivity for the respective products under the given conditions.
What is the role of the molten salt-assisted synthesis in achieving the desired catalyst structures?
The molten salt method allows precise control over the relative concentrations and spatial distribution of Cu and Ce-Ov sites, enabling the construction of two distinct geometries: Cu-rich (Cu10CeOx) and Ce-Ov-rich (CuCe10Ox) configurations. This control is essential for tuning the reaction pathway.
Are there any scalability concerns for industrial application of these catalysts?
The molten salt-assisted synthesis is a scalable method, but the current study focuses on fundamental mechanistic insights. Further optimization of electrode preparation and long-term stability would be needed for industrial deployment, though the high FEs at moderate overpotentials are promising.
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