Tunable work function via rare earth oxide interfacial engineering on graphite for electron transpiration cooling

Electron transpiration cooling (ETC) leverages thermionic energy conversion to enable non-ablative thermal management in hypersonic vehicles with sharp leading edges. To address the urgent requirement for low work function thermal cathode materials in ETC, this study developed a rare earth oxide interfacial engineering strategy for modulating the work function of graphite. The graphite-La₂O₃ composite (G-La₂O₃) with a precisely engineered multi-interfacial structure was synthesized via an in situ process involving chemical pretreatment, impregnation, and thermal reaction. Characterization confirmed that the G-La₂O₃ exhibits a work function reduction of 28.3% compared to pristine graphite. Density functional theory further elucidate the electronic origin of this reduction: electrons in both pristine graphite and La₂O₃ reside in bound states, whereas interfacial composite formation facilitates electron delocalization. Significant charge transfer occurs toward the heterointerface, generating delocalized electronic states, thereby lowering the surface work function. A fluidic model was developed to simulate ETC, wherein the experimentally determined work function of the material was incorporated as a user-defined parameter to investigate the influence of low work function on the cooling performance of ETC. This study provides an alternative strategy for fabricating thermal cathode materials and facilitates further experimental validation and implementation of ETC.