Modulating Orbital Hybridization in SrFeO _3-δ -Based Electrodes for Efficient Reversible Solid Oxide Cells

Reversible solid oxide cells offer manufacturing simplicity and operational versatility between power generation and energy conversion, yet their development is hindered by the low intrinsic activity and poor stability of conventional electrodes. Herein, Ce and Mo with 4f and 4d orbitals are successfully incorporated into the A and B sites of SrFeO 3-δ to form the Sr 0.9 Ce 0.1 Fe 0.9 Mo 0.1 O 3-δ (SCFM) double-perovskite electrode. The Ce 4f orbitals establish an asymmetric 4f-2p-3d electron bridge that facilitates charge transfer, while strong Mo–O π donation interaction enhances structural stability and promotes reactive oxygen vacancy formation. This high-order orbital hybridization endows the SCFM symmetric electrode with high electrocatalytic activity and durability in various conditions. In fuel cell mode, the SCFM symmetric electrode achieves power densities of 1.55 W cm –2 in H 2 /air at 800 °C and 0.41 W cm –2 in C 2 H 6 /air at 750 °C, with concurrent ethylene coproduction. Under the CO 2 electrolysis mode, it delivers a current density of 3.24 A cm –2 at 1.55 V with nearly 100% CO selectivity and Faradaic efficiency. This work presents an orbital-based asymmetric doping strategy for designing high-performance multifunctional electrodes for energy conversion technologies.