Single‐Atom Enables Reverse Hydrogen Spillover for High‐Performance Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs) offer a promising avenue for sustainable energy conversion, however, their commercial potential is hindered by sluggish proton-involved oxygen reduction reaction (P-ORR) kinetics and inadequate durability of cathode materials. Here, a novel single-atom Ru anchor on BaCe0.125Fe0.875O3-δ (BCF) perovskite, synthesized by a facile and scalable solid-state approach, as a potential cathode for PCFCs is reported. Theoretical and experimental analyses demonstrate that the single-atom Ru on BCF, characterized by a unique 4-coordinate Ru-O-Fe configuration, not only induces reverse hydrogen spillover but also acts as an active site for P-ORR. The application of the optimized 2Ru-BCF (2 wt.% Ru) cathode in a single cell delivers an exceptional peak power density of 1.78 W cm-2 at 700 °C, along with excellent operational stability over 200 h. These findings provide new insights into single-atom engineering, advancing the commercial viability of PCFCs.