Regulation of oxygen vacancy within oxide pyrochlores by F-doping to boost oxygen-evolution activity

The development of cost-effective and durable oxygen evolution reaction (OER) catalysts is an essential prerequisite for hydrogen production through proton exchange membrane water electrolysis. Herein, a series of F-doped pyrochlore yttrium ruthenate Y2Ru2O7−δ-xFx (YRuOF) are designed via low-temperature fluorination of precursor oxides with polyvinylidene fluoride. Both X-ray photoelectron spectroscopy and transmission electron microscopy results confirm that F is doped into the pyrochlore crystal lattice, inducing the oxygen vacancies (VO). Importantly, the OER catalytic activity is positively correlated with VO concentration. The density functional calculation (DFT) reveals that the existence of VO enhances the metal-oxygen covalency of pyrochlore, which is conducive to the lattice oxygen evolution mechanism, hence greatly accelerating the OER kinetic. Consequently, the optimized YRuOF catalyst exhibits a greatly enhanced OER activity with an overpotential of ~235 mV at 10 mA cm−2 in comparison with that on undoped pyrochlore (~296 mV). Furthermore, such a F-doped YRuOF catalyst has a very good OER stability. This study provides an ideal perspective to develop highly efficient and durable YRuOF for the oxygen evolution reaction.