Density functional theory (DFT)-guided interfacial engineering of alkaline-earth-oxide-infiltrated Ni–YSZ composite anodes for direct ammonia solid oxide fuel cells

초록

Interfacial engineering of ceramic–metal composite electrodes is a promising strategy for improving direct-ammonia solid oxide fuel cells (DA-SOFCs). Herein, alkaline-earth metal oxides (AEMOs; BaO, SrO, CaO, and MgO) were infiltrated into porous Ni–YSZ cermet anodes to create modified Ni–AEMO–YSZ interfacial regions. Density-functional theory and interfacial charge analyses showed that AEMO decoration lowers the Ni work function, with stronger effects for BaO and SrO than for CaO and MgO. The work function is interpreted as a supporting electronic descriptor rather than direct evidence of NH3 adsorption energies or N–H dissociation barriers. CO2-TPD and NH3-TPD showed promoter-induced changes in acid–base and adsorption characteristics, but the quantified desorption amounts did not follow the catalytic-activity order, indicating that neither total basicity nor total NH3 adsorption alone determines activity. BaO- and SrO-promoted catalysts exhibited lower apparent activation energies than pristine Ni–YSZ, while their similar values suggest that the higher BaO activity also involves differences in accessible interfacial-site density and apparent pre-exponential factors. TEM/STEM–EDS confirmed broad promoter distribution within the Ni–YSZ composites. Electrochemical tests under H2-containing and NH3 fuels showed that SrO and BaO improve both the intrinsic anode electrochemical response and direct-ammonia operation, indicating combined catalytic and electrochemical promotion. The cells maintained nearly stable voltage and impedance responses during 100 h of operation, supporting short-term stability. Overall, the promotion effect arises from the combined influence of interfacial electronic modification, acid–base characteristics, promoter distribution, and accessible reaction-site density. © 2026