Tailoring p–n heterojunction via high entropy cation integration to improve fuel cell performance

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Abstract Solid oxide fuel cells face significant challenges in achieving high ionic conductivity and operational stability at low temperatures. Here, we present a high entropy cation integration strategy to engineer next generation semiconductor ionic fuel cells. We synthesized a p-type high entropy Ruddlesden–Popper perovskite oxide, (La 0.2 Ca 0.2 Sr 0.2 Sm 0.2 Pr 0.2 ) 2 NiO 4+δ (HEO), and combined it with a conventional n-type ionic conductor, Sm 0.2 Ce 0.8 O 2–δ (SDC), forming HEO–SDC heterostructure membranes with varying mass ratios. The coherent, diffused interfaces (~2 nm domain boundaries), percolated cation networks, significant lattice strain, and abundant surface-active oxygen species, enhance electronic and ionic conductivity via Ni 2+ /Ni 3+ hole hopping. Interfacial heterojunctions establish a built-in electric field that suppresses electronic short circuiting while promoting ionic transport. The 5HEO–5SDC achieves a polarization resistance of 0.096 Ω cm 2 and a peak power density of 1034 mW cm −2 at 550 °C, with stable operation over 90 hours. These findings establish high entropy interface engineering as a transformative paradigm for energy conversion devices.

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