Tuning Ceramic-Metal Wettability of Nickel Cermets for Efficient and Durable Hydrogen Oxidation and Evolution in Protonic Ceramic Cells

Protonic ceramic cells are an emerging solid-state device for the efficient conversion between electricity and fuels. Ni cermet electrodes with a protonic ceramic matrix such as BaZr0.1Ce0.7Y0.2O3−δ (BZCY) are highly active for hydrogen oxidation and evolution reactions. Nevertheless, performance deterioration remains problematic for their practical applications due to poor ceramic–metal wettability and the resultant interfacial debonding. Here, we show that the catalytic durability of Ni-BZCY cermets can be effectively enhanced by introducing Ce0.8Gd0.2O2−δ (GDC) into the ceramic matrix, which acts as an anchoring component to thermodynamically promote Ni/BZCY wettability and thereby increases the microstructural stability, as demonstrated by phase-field modeling. Density-functional theory (DFT) calculations reveal more charge transfer from metallic Ni and larger adsorption energy of Ni clusters on GDC, yielding stronger ceramic–metal interaction and higher Ni wettability than on BZCY. Symmetrical protonic ceramic cells with GDC-modified Ni-BZCY cermet electrodes can produce a stable H2 pumping flux of 7.37 mL·min–1·cm–2 with an electricity consumption of 0.90 kWh·Nm–3 at 700 °C. This work highlights the critical role of interfacial wettability in typical heterogeneous electrocatalysis and offers some insights and practices for the design of highly durable catalysts.