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Photothermal Catalytic CO₂ Reduction: Activation Mechanisms at the Microscale, Industrial Application Prospects, and Future Perspectives

In a previous article titled "In-depth Understanding of the Basic Principles of Photothermal CO₂ Reduction Reaction," we introduced the research background, basic principles, and catalyst design strategies for photothermal catalysis of CO₂. This article will further explore the microscale mechanisms of CO₂ activation by photothermal functional materials, the industrial application prospects of photothermal catalytic CO₂ reduction, and future outlooks.


Microscale Mechanisms of Photothermal CO₂ Activation

1. Interface Electron Transfer Bridge Facilitating Carrier Separation at the Interface

Due to the rich oxygen-containing groups and surface terminal groups on the surface of photothermal functional materials, after forming a heterojunction, a chemical bond is formed through the interaction of terminal groups with the other surface. This bond causes potential differences and band rearrangement, acting as an "electron transfer bridge" that promotes charge transfer at the interface. The presence of an electron bridge significantly improves the efficiency of charge transfer, accelerates carrier migration, and facilitates the activation of photothermal CO₂.

Electron transfer bridge constructed between oxygen-containing groups on the surface and Cu

Figure 1. Electron transfer bridge constructed between oxygen-containing groups on the surface and Cu[1]

2. "Electron-Thermal-CO₂" Synergistic Center Promoting Photothermal Synergistic CO₂ Activation

As carriers migrate through the electron transfer bridge to the interface, photothermal materials become accumulation sites for heat, electrons, and CO₂ due to their excellent photothermal capability, electron enrichment ability, and CO₂ adsorption capability. At higher photothermal temperatures, energy-mass transfer processes such as carrier and reactant migration are enhanced, and electrons quickly gather at the surface of the photothermal material, forming a rich electron surface. Meanwhile, the surface of the photothermal material adsorbs a large amount of CO₂, and many electrons quickly activate the adsorbed CO₂ at high temperatures. The "electron-thermal-CO₂" synergistic center is crucial in the photothermal catalytic CO₂ reduction process.


Industrial Application Prospects of Photothermal Catalytic CO₂ Reduction

1. Industrial Application of Photothermal Catalytic CO₂ Reduction with External Heat Source Heating

There are mainly two modes of energy supply: one is to use an external heat source for heating while introducing sunlight; the other is to simultaneously introduce sunlight and a heat source in a concentrated manner. However, it is not recommended to provide an external heat source through methods such as electric heating and combustion, as using electricity and fuel for heating can lead to a significant amount of energy consumption and pollution issues, contradicting the sustainability and cleanliness of photothermal catalysis. In mode one, it is correct to use waste heat and pressure in industrial production as an external heat source for photothermal catalytic CO₂. This is a win-win solution for CO₂ reduction, recovering thermal energy, and fuel regeneration.

2. Industrial Application of Concentrated Photothermal Catalytic CO₂ Reduction

Compared to external heat source heating (120~350°C), sunlight concentration can raise the reaction temperature to as high as 500~1000°C[2]. The higher reaction temperature greatly promotes the smooth progress of photothermal catalytic CO₂ reduction[3-5]. Concentrated photothermal catalytic reactions derive their energy entirely from solar energy, exhibiting good sustainability and cleanliness[6]. However, the industrial development of concentrated photothermal catalytic CO₂ reduction has strong regional characteristics, depending on the spatial distribution of solar radiation intensity. Although the development and application of solar concentrators are relatively mature, the technology of using concentrated solar energy for photothermal catalytic CO₂ reduction is still in the stage of further exploration, and achieving small heat losses and high heat transfer capacity is crucial.

Industrial application example of concentrated photothermal catalytic CO₂ reduction

Figure 2. Industrial application example of concentrated photothermal catalytic CO₂ reduction[7]

Challenges and Outlooks

1. For photothermal catalysis, the energy and mass transfer processes of solar light absorption and photothermal conversion have a decisive impact on the generation of carriers and the photothermal temperature.

The innovative annular reactor of the PLR-RP series catalytic reaction evaluation device limits the thickness of the catalyst bed to 3 mm. This ensures effective illumination of the catalyst and increases the light-receiving area of the catalyst, improving the absorption efficiency of sunlight and ensuring maximum light and heat synergistic catalytic reaction.

PLR-RP series catalytic reaction evaluation device

2. Designing simple, low-cost, and non-secondary pollution photothermal catalysts, while paying attention to the yield, cost, and environmental issues of photothermal catalysts.

3. Design and develop efficient, stable, and minimally heat-loss catalysts and reaction devices suitable for large-scale concentrator reactors.

The PLR-RP series catalytic reaction evaluation device with a preheating-assisted heating module can effectively reduce the temperature gradient between the catalyst and the reaction system, thereby reducing heat loss in photothermal catalytic reactions and ensuring the reliability of experiments.

4. Explore the potential mechanisms of reaction pathways in photothermal catalytic CO₂ reduction systems.

Interpretation of the literature section is only a translation and summary by the author based on the references. If there are any errors, please feel free to correct them!

Article Information

Wang, Z.; Yang, Z.*, Kadirova, Z. C.; Guo, M.; Fang, R.; He, J.; Yan, Y.; Ran, J., Photothermal functional material and structure for photothermal catalytic CO₂ reduction: Recent advance, application and prospect. Coordination Chemistry Reviews 2022, 473, 214794.