Ji-Won Son

To lower the operation temperature of solid oxide fuel cells, thin-film electrolytes have attracted considerable attention, but their chemical instability and mechanical defects hinder their performance. To address these issues, gadolinia-doped ceria (GDC)–yttria-stabilized zirconia (YSZ)–GDC trilayer (CZC) thin-film electrolytes have been developed, wherein the fuel-side GDC layer provides high ionic conductivity and densifies the YSZ, and the cathode-side GDC chemically protects the YSZ electrolyte from the lanthanum strontium cobaltite cathode. Electrochemical impedance spectroscopy shows that the measured ionic conductance of CZC electrolytes is 3–4 times higher than the simple sum of the single-layer conductance of YSZ and GDC in series. This enhancement does not depend on the growth temperature, as low-temperature-deposited then annealed films perform comparably to their high-temperature-grown counterparts. X-ray diffraction and electron microscopy reveal that the YSZ layer in the CZC electrolytes forms highly continuous columnar grains with a markedly decreased grain boundary density, minimizing lattice discontinuities along the ion transport pathways. Grain-orientation mapping confirms predominantly low-angle columnar boundaries rather than the highly misoriented interfaces that would impede ion transport. These observations suggest that the CZC trilayer conductance is enhanced by the single-crystal-like columnar growth of YSZ, facilitated by its crystallographic compatibility with the underlying GDC. Collectively, these findings establish the practicality of CZC trilayers as a high-performance thin-film electrolyte operable at lower temperatures, providing microstructural design guidelines for interface-engineered solid oxide ion conductors. This approach highlights how interface-guided microstructural engineering can unlock unexpected transport properties in such conductors, offering broad implications for next-generation energy devices.

The rate-determining step of proton-coupled oxygen reduction is identified by correlating intrinsic cathode thermodynamics and kinetics with a generalized microkinetic model.

We developed a highly dispersed Ru nanocatalyst (∼6 nm) via exsolution on BCZY, enabling high ammonia synthesis at 1 atm. TGA precisely quantified the exsolution degree (>96% at optimal conditions) and clarified that Ru nanoparticle formation proceeds through a strain-limited exsolution mechanism.

Cr species and CO₂ rapidly degrade the PCFC electrolyte BaCe_0.4Zr_0.4Y_0.1Yb_0.1O_3−δ, while the air electrode PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ remains stable. A thin PBSCF layer enhances air electrode/electrolyte interface stability.

The energy transition from fossil fuel-based to renewable energy is a global agenda. At present, a major concern in the green hydrogen economy is the demand for clean fuels and non-noble materials to produce hydrogen through water splitting. Researchers are focusing on addressing this concern with the help of the development of appropriate non-noble-based photo-/electrocatalytic materials. A new class of two-dimensional materials, MXenes, have recently shown tremendous potential for water splitting to produce H₂via a photoelectrochemical process. The unique properties of emerging 2D MXene materials, such as hydrophilic surface functionalities, higher surface-to-volume ratios, and inherent flexibility, present these materials as appropriate photo-/electrocatalytic materials. Unique value addition and innovative strategies such as the introduction of end-group modification, heterojunctions, and nanostructure engineering have shown the potential of MXene materials as emerging photo-/electrocatalysts for water splitting. When integrated with conventional noble metal catalysts, MXene-based catalysts demonstrated a lower overpotential for hydrogen and oxygen evolution reactions and a remarkable boost in performance for enhanced H₂ production rates surpassing those of pristine noble metal-based catalysts. These promote future perspectives for the utilization of chemically synthesized MXenes as alternative photo-/electrocatalysts. Future research direction should focus on MXene synthesis and utilization for surface modification, composite formation, stabilization, and optimization in synthesis methods and post-synthesis treatments. This review highlights the progress in the understanding of fundamental mechanisms and issues associated with water splitting, influencing factors of MXenes, their value addition role, and application strategies for water splitting, including performance, challenges, and outlook of MXene-based photo-/electrocatalysts, in the last five years.

The phase separation of CZO involves a structured process delineated into three key reaction steps: (1) transformation into defect fluorite, (2) conversion into the pyrochlore structure, and (3) complete separation into Ce₂O₃ and ZrO₂ phases.

This study reports a high-performance solid oxide fuel cell system with rapid thermal cycling and cold start-up (i.e., ready-to-use) for mobile applications. This system reached 600 °C within 5 min of start-up and exhibited maximum power of 1.123 W.