Hyung-Tae Lim

Proton-conducting ceramic cells (PCCs) enable high-efficiency energy conversion and storage at intermediate temperatures (400–600 °C) while offering lower operational costs and improved durability compared to oxygen-ion-conducting cells. However, their adoption is limited by their low electrocatalytic activity and high polarization resistance. Electrode surface modification has emerged as a compelling strategy for improving electrode activity and durability. This Review examines three approaches that have demonstrated performance enhancements in PCCs: (1) infiltration of catalytically active materials into a porous electrode scaffold, (2) exsolution of metallic and oxide phases under tailored redox conditions to generate active sites, and (3) pulsed laser and atomic-layer thin-film depositions for surface engineering. The fundamental mechanisms and crucial physical factors underlying each strategy are discussed, along with advanced characterization techniques that provide insight into the in situ growth, structural evolution, and phase transformation of active materials. Finally, we highlight the challenges associated with these techniques and recommend future research directions to accelerate the development of PCC technology for commercial applications.

This study examined the effects of localized degradation and Ni–Co coating in a large-area solid oxide fuel cell (SOFC) operated under hydrogen and direct ammonia fueling. Comparable electrochemical performances were achieved under both conditions, with the exception of the power density loss caused by the high contact resistance in the test configuration. Complete ammonia conversion occurred at 650 °C under a low normalized flow rate with a large active area, emphasizing the importance of the residence time. Post-test analyses revealed pronounced degradation in the inlet region of the anode and the current collector, where repeated nitridation/reduction cycles led to Ni particle coarsening, microstructural collapse, and weakening of the current pathways. In contrast, the outlet region exhibited minimal structural changes, confirming that degradation was highly site-specific. Ammonia exposure tests performed on ferritic stainless-steel interconnectors demonstrated that the Ni–Co coating suppressed nitride formation and preserved the structural integrity, mitigating nitrogen ingress. These results indicate that the durability challenges associated with direct-ammonia SOFCs are governed by localized inlet-side degradation. Region-specific protection of the anode and current collector, together with Ni–Co coating, are proposed as practical strategies to improve the long-term stabilities and reliabilities of SOFC stacks under direct ammonia operation.

All-solid-state lithium–sulfur batteries with Li_xSi anodes are evaluated. The optimal composition for practical cell design is identified as x = 1.71 and N/P ratio = 2.05, enabling the realization of high electrochemical performance and stability.