Oxygen vacancy engineering of yttrium ruthenate pyrochlores as an efficient oxygen catalyst for both proton exchange membrane water electrolyzers and rechargeable zinc-air batteries

We for the first time demonstrate that oxygen electrocatalysts can be synchronously applied and stably operated in both proton exchange membrane water electrolyzers (PEMWE) and zinc-air batteries (ZAB) devices. The electrocatalyst (Y1.75Ca0.25Ru2O7) optimized by oxygen vacancy engineering demonstrates superior electrocatalytic activity and durability for both oxygen evolution reaction and oxygen reduction reaction. For PEMWE, it achieves 1.25 A cm(-2) under a cell voltage of 1.7 V at 60 degrees C and operates stably for more than 1000 min at 60 degrees C. For ZAB, Y1.75Ca0.25Ru2O7 operates stably over 6400 min and degrades only slightly. Our results reveal that partial Ca2+ replacement of Y3+ in Y2Ru2O7 promotes the hole doping effect, and thus enhances the oxygen vacancy concentration and hybrid valence of Ru4+/Ru5+, which are strongly associated with the electrochemical performance of oxygen electrocatalysts. This work paves a new avenue for developing active and robust oxygen electrocatalysts for both PEMWE and ZAB.