Strengthening the BZCYYb electrolyte/cathode interface for protonic ceramic fuel cells via Ni doping and in situ exsolution

A reliable electrolyte/electrode interface is crucial to the performance of protonic ceramic fuel cells (PCFCs), yet the poor sinterability of proton-conducting electrolytes and their limited interfacial bonding with cathodes remain challenging. This study proposes a synergistic modification strategy combining Ni doping and in situ exsolution (ISE) to enhance the interfacial bonding between the BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) electrolyte and the PrBaCo 2 O 5+δ (PBC12) cathode. Ni doping induces lattice contraction and promotes grain growth and densification of BZCYYb, increasing the average grain size from 6.82 μm to 14.5 μm. Subsequent ISE treatment under 5% H₂–95% Ar at 650 °C for 20 h generates uniformly distributed Ni nanoparticles with sizes of 20–50 nm on the electrolyte surface, accompanied by an increased surface Ce 3+ /Ce 4+ ratio and oxygen-vacancy-related species. During subsequent oxidative co-sintering with PBC12, the Ni-derived surface species promote intimate electrolyte/cathode contact and enhance interfacial bonding. As a result, the interfacial shear strength increases from 12.6 MPa to 19.7 MPa, corresponding to a 56.3% improvement, while the area-specific resistance of PBC12/ISE-BZCYYbNi/PBC12 symmetric cells is also reduced. These results demonstrate that coupling Ni doping with surface exsolution provides an effective strategy for simultaneously improving the sinterability of BZCYYb and the mechanical properties of its interface with PBC12.