Pyrochlore Electrocatalyst for Cathodes in Potassium-Oxygen Batteries

Metal−oxygen (M−O 2 ) batteries promise some of the highest theoretical energy densities amongst battery systems (Li-O 2 ~3458 Wh/kg, Na-O 2 ~1605 Wh/kg, K-O 2 ~935 Wh/kg). Despite the high energy density, Li-O 2 batteries suffer critical challenges such as high overpotential, limited cycle life and low practical capacities. 1 In this context, K−O 2 batteries received greater attention as it exhibits the lowest charge/discharge overpotentials (50 mV), high stability and reversibility of the superoxide product (KO 2 ) formed via a single electron transfer reaction. This is in contrast to the higher charge overpotentials (1000 mV/200 mV) and peroxides products formed in Li–O 2 /Na–O 2 batteries. 2 The choice of DMSO as an electrolyte for K-O 2 batteries, due to its high donor number and KO 2 production was previously studied in our group. 3,4 In this work, 1M potassium triflate in DMSO is used as electrolyte and different platinum and pyrochlore-based electrocatalyst (Pb 2 Ru 2 O 7-x ) are studied to enhance oxygen reduction reaction (ORR) activity. The charge-discharge polarization was further studied using a symmetric cell with carbon felt and Pb 2 Ru 2 O 7−x coated carbon felt using DMSO-based K + electrolytes. The cathode electrodes are characterized using Raman and SEM-EDX. Chem Rev. 2020 , 120, 6626–6683; 2. J. Phys. Chem. Lett . 2020 , 11, 7849–7856; 3. J. Phys. Chem. C 2018 , 122, 19319–19327; PNAS . 2019 , 116, 14899-14904 Figure 1