Zinc triggers favorable hydrogenation reaction in double perovskite PrBaCo₂O₆-δ: Applications in protonic ceramic cells

Protonic ceramic cell is seen as the next-generation energy conversion device designed to efficiently and reversibly convert chemical energy into electricity working at intermediate temperatures. However, their practical application heavily relies on the development of high-performance air electrodes. Mixed proton/electron/oxygen-ion conducting materials have promising potential as superior air electrodes, as they can significantly boost activity by extending active sites to the entire air electrode. Herein, we introduce 5 mol% hydrophilic Zn into PrBaCo₂O₆-δ resulting in the PrBaCo_1.9Zn_0.1O_6-δ (PBCZn10), which exhibits enhanced proton uptake ability and excellent stability in steam-concentrated atmospheres. The electrochemical characterization results demonstrate that introducing Zn into PBC significantly reduces the polarization resistance by 45 % under 10% H₂O/air at 550 °C. Applying such novel air-electrode on real electrochemical devices nearly doubled the out-put performance to 655 mW cm⁻² at 650 °C. This confirms that the enhanced proton uptake ability in PBCZn10 facilitates proton interfacial transport and extends the reaction zone. Importantly, our study offers an insightful view into the proton uptake process and the surface evolution of the material before and after proton uptakes, employing high-temperature XRD and depth-profiling XPS. This work provides valuable guidance for developing triple electronic-ionic conducting oxides by shedding light on the proton uptake process on electrode materials.