Solid oxide fuel cells (SOFCs) represent a highly efficient energy conversion technology capable of directly transforming chemical energy into electricity with minimal environmental impact. A critical component of SOFC performance lies in the electrode materials, where nanostructured designs have significantly enhanced ionic and electronic conductivity, catalytic activity, and thermal stability. Recent advances in nanomaterials have enabled the development of high-performance electrodes, particularly focusing on nanostructured perovskites, doped ceria, and composite materials. These innovations address key challenges such as reducing operating temperatures while maintaining electrochemical performance and durability.

Perovskite-based materials, particularly lanthanum strontium manganite (LSM) and lanthanum strontium cobalt ferrite (LSCF), are widely used as SOFC cathodes due to their excellent mixed ionic-electronic conductivity (MIEC) and catalytic activity for oxygen reduction reactions (ORR). Nanostructuring these perovskites enhances their surface area and active sites, improving oxygen adsorption and dissociation. For instance, LSCF nanoparticles synthesized via sol-gel methods exhibit superior ORR kinetics compared to bulk counterparts, with area-specific resistances as low as 0.1 Ω cm² at 700°C. Doping strategies, such as substituting cobalt with iron or nickel, further optimize electronic conductivity while reducing thermal expansion mismatches with the electrolyte. Nanoscale engineering of perovskite surfaces, including the introduction of porous architectures, facilitates gas diffusion and triple-phase boundary (TPB) density, critical for high-performance cathodes.

Doped ceria materials, such as gadolinium-doped ceria (GDC) and samarium-doped ceria (SDC), serve as both electrolytes and anode components due to their high ionic conductivity at intermediate temperatures (500–700°C). Nanostructured ceria enhances oxygen ion mobility by introducing grain boundary effects and strain-induced conductivity improvements. For example, SDC nanoparticles with grain sizes below 50 nm demonstrate ionic conductivities exceeding 0.1 S/cm at 600°C, attributed to increased oxygen vacancy concentrations and shorter diffusion pathways. Composite anodes incorporating nickel and doped ceria (Ni-GDC or Ni-SDC) leverage nanoscale mixing to improve electrochemical performance. The percolation of nickel nanoparticles ensures electronic conductivity, while the doped ceria phase provides ionic conduction and catalytic activity for hydrogen oxidation. Optimizing the Ni-to-ceria ratio and particle size distribution minimizes polarization losses, with recent studies reporting anode polarization resistances below 0.15 Ω cm² at 650°C.

Composite electrodes combining perovskites, doped ceria, and metallic phases have emerged as a promising approach to enhance SOFC durability and efficiency. Infiltrating nanoparticles of LSCF into a porous GDC scaffold creates a hybrid cathode with extended TPBs and improved thermal cycling stability. Similarly, anode materials incorporating nickel-ceria-zirconia composites exhibit enhanced resistance to carbon deposition and sulfur poisoning, critical for operation with hydrocarbon fuels. Nanostructured composites also mitigate interfacial delamination issues between electrodes and electrolytes by reducing thermal stress through tailored coefficients of thermal expansion.

Synthesis techniques play a pivotal role in achieving precise control over nanomaterial properties. Wet chemical methods, including sol-gel and co-precipitation, enable homogeneous mixing of multi-component systems at the atomic level. For instance, the Pechini method facilitates the formation of phase-pure perovskite nanoparticles with controlled stoichiometry. Electrospinning produces nanofibrous electrodes with high porosity and interconnected networks, enhancing gas transport and electrochemical activity. Atomic layer deposition (ALD) allows for conformal coatings of catalyst nanoparticles on porous scaffolds, optimizing TPB density while minimizing material usage. Advanced characterization techniques, such as in-situ X-ray diffraction and impedance spectroscopy, provide insights into phase stability and conduction mechanisms under operating conditions.

Thermal stability remains a critical consideration for nanostructured SOFC electrodes, as prolonged operation at high temperatures can lead to particle coarsening and performance degradation. Strategies such as doping with refractory elements (e.g., zirconium in ceria) or incorporating secondary phases (e.g., alumina nanoparticles) inhibit grain growth while maintaining conductivity. Core-shell architectures, where a catalytically active shell surrounds a stable core, offer additional thermal stability. For example, LSCF-coated GDC core-shell particles demonstrate negligible performance loss after 1000 hours at 750°C, attributed to the suppression of cation interdiffusion.

Recent advances in nanostructured anodes focus on enhancing fuel flexibility and redox stability. Exsolved nickel nanoparticles from perovskite anodes (e.g., La₀.₄Sr₀.₄Ti₀.₉Ni₀.₁O₃) exhibit superior coking resistance and self-regenerating properties under reducing atmospheres. Similarly, copper-ceria-based anodes enable direct utilization of methane without external reforming, achieving power densities above 0.5 W/cm² at 650°C. Nanostructured cathodes have also seen progress, with layered perovskite oxides (e.g., PrBaCo₂O₅₊δ) demonstrating fast oxygen surface exchange kinetics due to ordered oxygen vacancy channels.

Optimizing the electrode-electrolyte interface is essential for minimizing interfacial resistances. Nanoscale interlayers, such as thin films of doped ceria between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, prevent chemical reactions and interdiffusion. Laser ablation and pulsed laser deposition enable precise fabrication of these interlayers with thicknesses below 100 nm, significantly reducing polarization losses. Furthermore, surface modification techniques, including plasma etching and electrochemical polishing, enhance adhesion and contact area at interfaces.

The integration of computational modeling accelerates the design of next-generation SOFC electrodes. Density functional theory (DFT) calculations predict dopant effects on oxygen vacancy formation energies in perovskites, guiding experimental synthesis. Finite element modeling simulates stress distributions in nanostructured composites, informing mechanical stability improvements. Machine learning algorithms analyze vast datasets to identify optimal compositions and processing parameters for high-performance electrodes.

In summary, nanomaterials have revolutionized SOFC electrode design by enabling precise control over composition, morphology, and interfacial properties. Nanostructured perovskites, doped ceria, and composite materials offer tailored functionalities that address key challenges in conductivity, thermal stability, and catalytic activity. Continued advancements in synthesis techniques and computational tools promise further enhancements in SOFC performance, driving the transition toward efficient and durable energy conversion systems.