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 BaZr_0.1Ce_0.7Y_0.2O_3-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 Ce_0.8Gd_0.2O_2-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.