Micro‐Grooving and Oxygen Vacancy Engineering Synergistically Enable Robust Interfaces in Protonic Ceramic Cells

Abstract Protonic ceramic fuel cells (PCFCs) are among the most promising high‐efficiency energy conversion systems. However, their performance is often constrained by the poor interface between the cathode and the electrolyte, limiting their practical applications. Herein, a strategy is presented to enhance the interface by applying femtosecond laser processing to the BaCe _0.7 Zr _0.1 Y _0.2 O _3‐δ (BCZY) electrolyte. The laser treatment effectively removes the inert surface layer and creates micro‐grooves coupled with nano‐protrusions, while simultaneously generating additional oxygen vacancies on the electrolyte surface. These physical and physicochemical modifications collectively improve the sintering performance between the electrolyte and cathode, resulting in a robust joining interface. Symmetrical cathode cells with the laser‐treated electrolyte show ≈50% reduction in the interfacial polarization resistance as well as enhanced stability. Furthermore, single cells demonstrate almost doubled peak power densities in the fuel cell mode. This work provides an efficient approach for engineering electrode‐electrolyte interfaces through femtosecond laser processing, thereby enabling significantly boosted PCFC performance.