New Multilayer Cobalt Catalyst Sets Benchmark for CO2 Reduction Efficiency

By Muhammad OsamaReviewed by Laura ThomsonOct 2 2025

A recent study published in the journal Applied Catalysis B: Environment and Energy introduced a novel multilayer cobalt phthalocyanine (CoPc) and carbon core-shell structure that enhances the electrocatalytic reduction of carbon dioxide (CO₂) to carbon monoxide (CO). This design challenges traditional single-molecule catalysts by delivering high conversion efficiency and improved electrocatalytic performance.

The findings represent an important step in electrocatalyst design, paving the way for more efficient carbon capture and utilization technologies that support global efforts to reduce CO₂ emissions and significantly advance sustainable energy solutions.

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Significance of Electrochemical CO₂ Reduction

Electrochemical CO₂ reduction (ECR) is a promising technology transforming CO₂, a major greenhouse gas, into valuable chemicals and fuels. It mitigates emissions and supports the integration of renewable energy and the sustainable production of hydrocarbons.

The efficiency of ECR depends on the choice of electrocatalysts, which start the conversion reactions. Metal-nitrogen-carbon (M-N-C) complexes, particularly cobalt phthalocyanine (CoPc), have gained significant attention due to their unique electronic properties and high catalytic activity. However, traditional single-layer catalyst models often oversimplify the active sites involved and may not fully leverage the catalytic potential of these materials.

Synthesis and Characterization of the Hybrid Catalyst

Researchers developed the multilayer CoPc and Ketjen Black (KB) hybrid catalyst to enhance CO₂ electroreduction. Using artificial intelligence-powered large-scale data mining (AIP-LDM), they screened 220 M-N-C materials and identified CoPc as a promising candidate. The catalyst was prepared by dissolving CoPc in dimethyl sulfoxide (DMSO), mixing it with KB, and applying the mixture to ultrasonic dispersion to achieve uniform adsorption. The resulting material was spray-coated onto carbon paper to create a gas diffusion electrode (GDE).

Electrochemical performance was tested in a custom three-electrode cell, optimized to maximize CO₂ delivery and minimize flooding. The cell setup included an Hg/HgO reference electrode and a platinum wire as the counter electrode. Characterization techniques, including X-ray absorption spectroscopy (XAS), Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were used to confirm the core-shell architecture and evaluate structural stability. Gas chromatography quantified CO production, providing insights into the catalytic efficiency of the CoPc/KB system.

Catalytic Performance and Mechanistic Insights

The outcomes demonstrated that the multilayer CoPc/KB core-shell structure significantly enhanced the electrocatalytic performance for CO₂ reduction, outperforming traditional single-layer models. The hybrid CoPc/KB electrode achieved a CO current density of -595 mA cm^-2 and a mass activity of 6537 A g^-1, while maintaining over 90% CO selectivity for approximately 100 hours at a current density of -100 mA cm^-2. These results establish a benchmark performance among reported phthalocyanine-based catalysts.

The enhanced performance depended on several factors. The multilayer arrangement facilitated self-driven surface charge transfer (SCT), which optimizes the Gibbs free energies of key CO₂ reduction intermediates and significantly improves reaction kinetics. Theoretical calculations supported these observations, showing that even minimal SCT moves the system closer to the peak of the volcano plot, correlating with optimal catalytic activity.

The unique polycrystalline arrangement of CoPc molecules on the KB support increased the specific surface area and reduced charge-transfer resistance. It strengthened electronic coupling between active sites and the carbon support. These effects improved electrochemical access to active sites and catalyst efficiency, suggesting that multilayer architectures more accurately represent the active units in practical catalytic systems.

Practical Applications for Sustainable Carbon Utilization

This research has significant implications for developing advanced electrocatalytic systems for CO₂ utilization. The multilayer CoPc/KB catalyst demonstrates superior performance while providing a scalable and cost-effective alternative to traditional catalysts.

By optimizing interactions between CoPc and carbon supports, the novel approach enhances CO₂ conversion efficiency, supporting the production of sustainable fuels and chemicals, and aligns with global efforts to reduce greenhouse gas emissions. As CO₂ electroreduction advances, the multilayer CoPc/KB structure could be integrated into larger-scale electrochemical systems, promoting the transition to renewable energy sources and a circular economy. Researchers showed how catalyst architectures, combined with data-driven techniques, can facilitate sustainable chemical production and reduce CO₂ emission.

Conclusions and Future Directions

This study highlights the critical role of multilayer CoPc/carbon structures in enhancing the electrocatalytic reduction of CO₂. By moving beyond the traditional single-molecule paradigm, the multilayer architecture demonstrates superior activity, high CO selectivity, and stable current densities, offering a promising pathway for efficient CO₂ conversion.

Future work should focus on optimizing the synthesis and multilayer architecture of CoPc/carbon catalysts, exploring other metal phthalocyanines, and evaluating the long-term stability and scalability of these systems. Integrating these materials into industrial-scale systems will be essential for translating laboratory successes into practical conversion technologies.

As the need to address climate change grows, innovations such as multilayer CoPc catalysts can facilitate the efficient conversion of CO₂ into valuable chemicals and fuels. Overall, this research advances the understanding of electrocatalytic mechanisms and highlights the importance of scalable approaches in developing sustainable energy solutions.

Journal References

Liu, T., & et al. (2025, February). Breaking the single-molecule paradigm: Multilayer cobalt phthalocyanine/carbon core-shell structure as the superior active unit for CO2-to-CO electroreduction. Applied Catalysis B: Environment and Energy, 381(125852). DOI: 10.1016/j.apcatb.2025.125852, https://www.sciencedirect.com/science/article/pii/S0926337325008355?via%3Dihub

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