N−N Heterostructure Sm2O3/ZnO Electrolyte with Enhanced Proton Conduction for Fuel Cell Application

Samarium oxide (Sm2O3) is a promising electrolyte for low-temperature fuel cells but lacks further exploration of performance optimization. Herein, we propose an effective approach to strengthen the proton transport characteristics via constructing a heterostructure interface in a Sm2O3/ZnO composite electrolyte. The constructed optimal 6Sm2O3-4ZnO cell device yields an improved peak power density of 920 mW cm–2 and an extended durability performance of 45 h at 500 °C. Experiments confirm the proton conduction, and the density functional theory calculation further discloses the low proton migration energy of 0.35 eV. The semiconductor junction test and theoretical calculation both reveal that the heterojunction exists at the Sm2O3/ZnO interface. The strong local electric field strength of 1.53 × 107 V m–1 at the interface effectively suppresses short circuit and accelerates proton transport, leading to significantly enhanced electrochemical performance. This study indicates that the 6Sm2O3-4ZnO material is a promising electrolyte candidate for fuel cell application.