Shuai Liu, Ruixi Qiao, Meiting Yang, Wei Feng, Baocheng Xiong, Desheng Feng, Guangming Yang, W. H. Huang, Min‐Hsin Yeh, Chih-Wen Pao, Zhiwei Hu, Xiaomin Xu, Wei Cao, Ran Ran, Wei Zhou, Yinlong Zhu
Heterointerfaces in composite electrodes play critical roles in catalytic performance, but methods for precise optimization of them are still lacking and remain challenging. Here, we propose an innovative ion-directional migration strategy to achieve precise optimization of heterointerfaces in a composite electrode of a solid oxide electrolysis cell (SOEC) for ultraefficient CO 2 electrolysis. Specifically, a composite electrode composed of Sr 2 Fe 1.5 Mo 0.5 O 6−δ perovskite and Ru 0.05 Ce 0.95 O 2 fluorite with a Ru loading of only 0.89 wt % (denoted as SFM-005Ru@CeO 2 ) is elaborately designed. Thermal treatment induces directed migration of Ru ions from the fluorite phase to the perovskite–fluorite heterointerfaces and subsurfaces of Sr 2 Fe 1.5 Mo 0.5 O 6−δ, enabling precise optimization of the oxygen vacancy concentration and the electronic environment of Fe cations inside the perovskite phase at the subsurface, thereby markedly enhancing O 2– /e – conductivity and CO 2 reduction reaction (CO 2 RR) activity. Impressively, a SOEC supported by an La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3−δ (LSGM, 140 μm) electrolyte and employing the SFM-005Ru@CeO 2 composite with a precisely optimized heterointerface as the cathode delivers an ultrahigh current density of 3.80 A cm –2 @1.5 V at 800 °C for direct CO 2 electrolysis, superior to all previously reported electrodes. It also shows excellent stability over 200 h under harsh operating conditions (750 °C, 1.6 A cm –2 ). This work opens up a new avenue to improve the performance of composite materials in various catalytic systems through precise heterointerface engineering.