Pr 6 O 11 : Temperature-Dependent Oxygen Vacancy Regulation and Catalytic Performance for Lithium-Oxygen Batteries.

Many challenges still exist in lithium-oxygen batteries (LOBs), particularly exploring an efficient catalyst to optimize the reaction pathway and regulate the Li 2 O 2 nucleation. Pr 6 O 11 has a unique 4f electronic structure and the highest oxygen ion mobility among rare earth oxides, exhibiting superior electronic, optical, and chemical properties. These unique properties might endow it with advanced catalytic activities for LOBs. This work reports two crystal forms of Pr 6 O 11 as novel catalysts and regulates the oxygen vacancy (V o ) concentrations by feasible calcination. Thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) confirm the conversion from commercial Pr 6 O 11 to cubic fluorite Pr 6 O 11 and V o -rich Pr 6 O 11 . Photographs, high-resolution transmission electron microscopy, selected area electron diffraction, XPS, and electron paramagnetic resonance robustly demonstrate the temperature-dependent evolution of V o . Ex situ XPS, scanning electron microscopy, and electrochemical techniques are used to study the catalytic mechanism and electrochemical reversibility. It is found that an appropriate V o concentration can boost O 2 adsorption/desorption, accelerate electron transport, and reduce the reaction energy barrier. V o -rich Pr 6 O 11 optimizes the reaction pathway by offering an intermediate Li 2- x O 2 (with metalloid conductivity) and adjusting Li 2 O 2 into vertically staggered nanoflakes, effectively avoiding the suffocation of the catalytic surface and presenting excellent capacity, cycling stability, and rate performance.