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Liquid Metal Catalysis for CO2 Conversion into Value-Added Chemicals

Illustration of CO2 conversion using liquid metal catalysis, showing CO2 molecules interacting with a liquid metal alloy surface.
Figure 1: This illustration depicts the mechanism of CO2 conversion using liquid metal catalysis. A liquid metal alloy phase (such as gallium or indium-based) interacts with CO2 molecules on its surface. The image highlights the incorporation of dopants or secondary metals within the alloy, affecting catalytic properties, and visualizes conversion products like formic acid and methanol. The cutaway view shows the fluid nature of the liquid metal, illustrating enhanced mass transfer and reaction pathways, underlining how the liquid alloy fosters efficient CO2 conversion processes.

Liquid metal catalysis, particularly involving gallium (Ga) and indium (In) based alloys, is a rapidly developing field presenting revolutionary possibilities for the sustainable conversion of carbon dioxide (CO2) into valuable chemicals. These innovative catalytic systems offer promising approaches to reducing greenhouse gas emissions while establishing new pathways for green chemical production. The unique properties of liquid metals—such as their tunable solubility, high CO2 affinity, and the ability to operate under mild conditions—distinguish them from conventional solid-state catalysts and drive interest in their scientific and industrial applications.

In this article, we explore breakthroughs in liquid metal-based CO2 catalysis, focusing on gallium and indium systems, discuss mechanistic insights, and outline the challenges and opportunities for future implementation.

Gallium-Based Liquid Metal Catalysts

A significant advantage of liquid metal catalysts is their capacity to activate and convert CO2 at relatively low temperatures—substantially lower than those required for traditional thermocatalysis. Gallium-based liquid metals, often combined with dopants or alloying elements, have demonstrated potential in both photocatalytic degradation of pollutants and direct CO2 utilization. For example, gallium-rich supported catalytically active liquid metal solutions (SCALMS) have undergone extensive investigation for dry reforming of methane—a process integrally related to CO2 utilization. Although some systems succumb to oxidation, the judicious selection of alloying elements, such as nickel (Ni), and optimal process conditions can overcome these stability challenges. Ga-Ni SCALMS exhibit activity based on a kinetically regulated redox process (Wolf et al., 2023).

Illustration showcasing the catalytic process and structure of gallium-rich SCALMS.
Figure 2: This 3D scientific render illustrates the catalytic process and structural characteristics of gallium-rich supported catalytically active liquid metal solutions (SCALMS). At its core, the image features a cross-section of a gallium-nickel alloy interface. CO2 molecules are shown interacting with the liquid metal, with color gradients highlighting the redox processes, symbolizing oxidation and reduction. The fluidity of the liquid metal catalyst is represented through a smooth texture, indicating its dynamic nature. The image contrasts solid versus liquid catalysts by depicting the mitigation of coking—solid carbon particles are shown being absorbed rather than accumulating, emphasizing SCALMS' advantage in preventing deactivation issues compared to solid catalysts. The dark background directs focus toward these intricate interactions, presenting an advanced view of catalysis at the molecular level.

The use of liquid metals in electrocatalytic systems is also gaining traction. These catalysts hold promise for the electrochemical conversion of CO2 to formic acid and other C1 chemicals, with the fluid phase helping to mitigate issues like coking and deactivation often associated with their solid counterparts.

Indium-Based Liquid Metal Catalysts and Derivatives

Indium-based systems are prominent contenders in the arena of CO2 catalytic conversion. Indium-containing metal–organic frameworks (MOFs) have emerged as efficient photocatalysts and electrocatalysts. For instance, In-MOF/graphene oxide heterostructures maintain robust CO2 reduction activity even in oxygen-rich environments (Zhang et al., 2024). Another avenue involves In2O3-based catalysts—sometimes promoted with palladium—that deliver potent activity and selectivity for the hydrogenation of CO2 to methanol (Stangeland et al., 2020; Frei et al., 2019).

These remarkable properties are largely attributed to indium's electronic structure and the presence of oxygen vacancy-rich surfaces, which facilitate efficient CO2 activation and conversion. Modifying the catalyst composition and architecture allows fine-tuning of product selectivity and efficiency. Such tunability, combined with high Faradaic efficiency in electrocatalytic systems, makes indium derivatives an area of strong research focus.

Conceptual illustration of palladium-enhanced In2O3 catalyst for CO2 hydrogenation to methanol, showing surface oxygen vacancies, CO2 adsorption and activation, intermediates, and electron pathways.
Figure 3: This conceptual illustration depicts the electrocatalytic reaction network in In2O3-based catalysts promoted with palladium for the conversion of CO2 to methanol. It visualizes the surface oxygen vacancies where CO2 molecules are adsorbed and activated, transitioning through intermediates towards methanol production. The molecular pathways demonstrate how electron flow facilitates the reaction, while the presence of palladium on the catalyst enhances selectivity and activity. The lattice structure is shown in a side-view, emphasizing the role of palladium in improving performance at the atomic level. The illustration uses vibrant colors and a dark background to highlight the complex molecular interactions and energy exchange processes involved.

Photothermal and Photoelectrocatalytic Approaches

Another highly promising domain is the photothermal and photoelectrocatalytic conversion of CO2, sometimes incorporating liquid metal components or their derivatives. These solar-driven systems are designed to mimic key aspects of natural photosynthesis, and nanocatalysts featuring liquid metal-like properties are integral to their function (Cheng et al., 2025). At the heart of these systems are plasmonic effects, where metallic nanoparticles boost light absorption and create hot electrons capable of driving CO2 reduction at the liquid metal surface. This provides a pathway to couple CO2 conversion with renewable energy sources.

Conceptual depiction of photothermal and photoelectrocatalytic CO2 conversion using liquid metal-inspired nanocatalysts.
Figure 4: This futuristic 3D render illustrates the process of photothermal and photoelectrocatalytic CO2 conversion using liquid metal-inspired nanocatalysts. Solar illumination impacts plasmonic nanoparticles, generating hot electrons that interact with CO2 molecules on a self-healing liquid metal surface. The energy flow is vividly depicted using neon highlights, demonstrating the catalytic transformation process. Set against a dark scientific background, this image highlights the innovative use of nanostructures and their interactions during CO2 conversion.

Critical hurdles for these approaches include ensuring the stability and durability of catalysts under intense illumination and fluctuating conditions. However, the potential of liquid metal surfaces for self-healing and regeneration offers significant advantages in overcoming deactivation and prolonging catalyst lifetime, making them attractive for integrated solar conversion technologies.

Challenges and Future Directions

Despite the clear promise of liquid metal catalysis for CO2 conversion, several hurdles must be overcome to realize their widespread deployment. Chief among these are issues of long-term stability, particularly under oxidative or high-temperature conditions, and the potential for leaching of active components. Additionally, a more nuanced mechanistic understanding is necessary—particularly regarding the atomic-level interaction between CO2 and the dynamic liquid metal surface, the formation and stabilization of intermediates, and control over product selectivity (Ye et al., 2019).

Advanced theoretical modeling, such as density functional theory (DFT) combined with sophisticated in-situ and operando experimental techniques, will be pivotal in unraveling these mechanisms. Recent innovations, such as engineered bismuth (Bi) catalysts with tensile strain, provide new approaches to activating previously inert sites (Chen et al., 2025). Achieving industrial-scale applications will also require the development of robust reactors, innovative product separation strategies, and possibly manufacturing advances like 3D-printed electrodes (Wang et al., 2025). The pursuit of co-hydrogenation of CO and CO2, as well as hybrid material systems, further underscores the vast scope and ambition of research in this area (Li et al., 2025).

Conclusion

Liquid metal catalysis stands as a novel and compelling technological frontier in the pursuit of sustainable CO2 conversion and valorization. Gallium and indium-based systems, integrating properties such as high tunability, mild operational conditions, and inherent self-healing behavior, are catalyzing new avenues for chemical production derived from greenhouse gases. Nevertheless, progress toward commercial realization depends on addressing stability, in-depth mechanistic elucidation, and scalable process engineering.

Continued interdisciplinary research efforts, combining catalyst innovation with advanced characterization and process design, will be essential for unlocking the potential of liquid metal catalysts. The synergistic integration of solar energy, hybrid material strategies, and dynamic liquid metal interfaces is expected to drive the development of efficient, circular carbon technologies for the future.

References

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