Interfacial Disordering and Heterojunction Enabling Fast Proton Conduction

The interfacial disorder is a general method to change the metal-oxygen compatibility and carrier density of heterostructure materials for ionic transport modulation. Herein, to enable high proton conduction, a semiconductor heterostructure based on spinel ZnFe₂O₄ (ZFO) and fluorite CeO₂ is developed and investigated in terms of structural characterization, first principle calculation, and electrochemical performance. Particular attention is paid to the interfacial disordering and heterojunction effects of the material. Results show that the heterostructure induces a disordered oxygen region at the hetero-interface of ZFO-CeO₂ by dislocating oxygen atoms, leading to fast proton transport. As a result, the ZFO-CeO₂ exhibits a high proton conductivity of 0.21 S cm⁻¹ and promising fuel cell power output of 1070 mW cm⁻² at 510 °C. Based upon these findings, a new mechanism is proposed by focusing on the change of O–O bond length to interpret the diffusion and acceleration of protons in ZFO-CeO₂ on the basis of the Grotthuss mechanism. This study provides a new strategy to customize semiconductor heterostructure to enable fast proton conduction.