Densely-neighbored-Ru nanoparticles confined in porous-SiO2 shell for efficient CO2 methanation via plasmon-coupling-enhanced photo-thermal catalysis

Background：

Plasmonic metal nanostructures (e.g., Au, Cu, Pt, Ru) have attracted considerable attention in photothermal catalysis due to their unique capabilities in light-field regulation and energy conversion. Owing to the localized surface plasmon resonance (LSPR) effect, these nanostructures can overcome the diffraction limit and amplify local electromagnetic fields, thereby enabling efficient conversion of light energy into localized thermal effects and high-energy carriers. Nevertheless, conventional supported catalysts are constrained by narrow spectral response and inefficient thermal utilization. Embedding metal nanoparticles within dielectric matrices (e.g., SiO₂, MXene) is widely recognized as an effective strategy to strengthen light-matter interactions and reduce thermal radiative losses. However, architectures based on isolated particles still suffer from restricted photogenerated response and limited electric field enhancements, which hinder efficient light-to-chemical energy conversion.

Studies have demonstrated that plasmonic coupling between adjacent nanoparticles can induce strong localized electromagnetic fields within sub-nanometer gaps, where the field intensity increases as the interparticle distance decreases. Notably, closely neighbored nanoparticle assemblies further intensify these fields, which are expected to promote reactant adsorption and activation via hot-electron injection or interfacial excitation. In addition, collective coupling between nanoparticles can induce pronounced macroscopic thermal effects, which are more advantageous than single-particle heating in enhancing photo-thermal catalytic performance. However, how to fully exploit the photothermal and photoelectronic contributions of densely packed nanoparticles embedded in dielectric matrices, while simultaneously addressing microscale thermal management, remains underexplored and present a major challenge for the rational design of high-performance plasmonic photothermal catalysts.

Research Progress：

Professor Baowen Zhou’s team at Shanghai Jiao Tong University, in collaboration with Professor Fenglong Wang’s team at Shandong University, has developed a new strategy to optimize the catalytic efficiency of photothermal catalysts. Based on finite-element method (FEM) simulations, the team systematically demonstrates that densely packed Ru nanoparticles confined within a pSiO₂ dielectric matrix generate pronounced plasmonic “hot spots”, markedly enhance localized electromagnetic fields, and thus facilitate efficient photon energy conversion. Meanwhile, the intrinsic thermal insulation of pSiO₂ suppresses heat dissipation, thereby enabling efficient nanoscale thermal management. Compared with conventional surface-loaded (Ru_m/pSiO₂) and isolated (Ru₁@pSiO₂) systems, this plasmonic coupling-confined architecture provides pronounced advantages in the synergistic regulation of photoelectronic and thermal fields.

Inspired by this theoretical insight, the team developed an optimized silica encapsulation strategy that enabled stable and controllable pSiO₂ shell growth while preserving the nanoscale proximity between Ru nanoparticles, thereby constructing photothermal nanoreactors (Ru_m@pSiO₂), in which closely neighbored Ru nanoparticles are confined within the pSiO₂ shell. To validate their catalytic functionality, photo-thermal CO₂ methanation was employed as a model reaction. At 250 ℃ under light irradiation, the optimized Ru_m@pSiO₂-2 catalyst exhibited a CH₄ production rate of 8.75 mol g_Ru⁻¹ h⁻¹ with nearly 100% selectivity, representing 3.2- and 2.6-fold enhancements over Ru_m/pSiO₂ and Ru₁@pSiO₂, respectively, and outperforming state-of-the-art photothermal catalysts. Remarkably, even under low winter temperatures (−4–6 ℃) and natural sunlight, the catalyst still delivered a CH₄ yield of 2.26 L g_cat⁻¹ h⁻¹, highlighting its practical application potential.

The researchers found that, compared with Ru_m/pSiO₂ and Ru₁@pSiO₂, the Ru_m@pSiO₂ nanostructure exhibits superior light-harvesting capability and spectral response, leading to elevated microscopic temperature fields under illumination and thus facilitating the reaction. Theoretical calculations and experimental characterizations further revealed that the strong localized electromagnetic fields induced by plasmonic coupling significantly enhance CO₂ adsorption and activation while facilitating H₂ dissociation. Moreover, compared to thermal catalysis alone, light irradiation further accelerates the conversion of *CO intermediate, thereby promoting CH₄ formation. Collectively, this unique Ru_m@pSiO₂ nanoreactor synergistically integrates plasmonic coupling, electromagnetic field confinement, and nanoscale thermal management, thereby creating a favorable reaction microenvironment that significantly enhances the overall efficiency of photo-thermal CO₂ methanation.

Perspective:

This study reveals that compared with conventional surface-supported and isolated systems, confining closely neighbored Ru nanoparticles within a pSiO₂ dielectric shell enables efficient utilization of plasmon-derived energy to drive photo-thermal CO₂ methanation. The nanoreactor architecture synergistically integrates strong plasmonic coupling, electromagnetic field confinement, and nanoscale thermal management, achieving excellent CH₄ yields with nearly 100% selectivity and maintaining high activity even under low ambient temperatures and natural sunlight. This “dielectric-matrix-confined plasmonic metal assemblies” strategy offers a universal paradigm for the rational design of next-generation high-performance photothermal catalysts. Beyond Ru, the approach can be extended to other plasmonic metal systems to precisely regulate optoelectronic and photothermal properties, thereby facilitating the efficient conversion of various key reactions in CO₂ valorization, solar energy conversion, and sustainable energy utilization.

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