Junjiao Li,Jun Xie,Dongchen Li,Lei Yu,Chaowei Xu,Senlin Yan,Yuzheng Lu
Interface engineering can be used to tune the properties of heterostructure materials at an atomic level, yielding exceptional final physical properties. In this work, we synthesized a heterostructure of a p-type semiconductor (NiO) and an n-type semiconductor (CeO2) for solid oxide fuel cell electrolytes. The CeO2-NiO heterostructure exhibited high ionic conductivity of 0.2 S cm−1at 530 °C, which was further improved to 0.29 S cm−1by the introduction of Na+ions. When it was applied in the fuel cell, an excellent power density of 571 mW cm−1was obtained, indicating that the CeO2-NiO heterostructure can provide favorable electrolyte functionality. The prepared CeO2-NiO heterostructures possessed both proton and oxygen ionic conductivities, with oxygen ionic conductivity dominating the fuel cell reaction. Further investigations in terms of electrical conductivity and electrode polarization, a proton and oxygen ionic co-conducting mechanism, and a mechanism for blocking electron transport showed that the reconstruction of the energy band at the interfaces was responsible for the enhanced ionic conductivity and cell power output. This work presents a new methodology and scientific understanding of semiconductor-based heterostructures for advanced ceramic fuel cells.
To understand the underlying mechanism of the interfacial charge transfer and local chemical state variation in the nonprecious-based hydrogen evolution reaction (HER) electrocatalysts, a model system of the NiO/CeO 2 heterostructure was chosen for investigation using a combination of the advanced electron microscopic characterization and first-principles calculations. The results directly proved that interfacial charge transfer occurs from Ni to Ce, leading to reduction in the valence state of Ce and increased formation of V O . This would optimize ΔG H* and facilitate the hydrogen evolution process, resulting in outstanding HER performance in 1 M KOH with a low overpotential of 99 mV at the current density of 10 mA•cm −2 and a modest Tafel slope of 78.4 mV•dec −1 for the NiO/CeO 2 heterostructure sample. Therefore, the improved HER performance could be attributed to the synergistic coupling interactions and electron redistribution at the interface of NiO and CeO 2 . These results concretely demonstrate the direct determination of the interfacial structure of the heterostructure and provide atomistic insights to unravel the underlying mechanism of interfacial charge transfer induced HER performance improvement.
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