Single atomic Ag enhances the bifunctional activity and cycling stability of MnO2

Heterogeneous electrocatalyst with single atom feature has attracted great interests. Although significant progress has been made on constructing and understanding carbon supported single atom electrocatalysts (SAECs), few attentions has been paid to metal oxide supported SAECs. The effect of single atom in enhancing electro-catalytic activity and stability of metal oxides has been poorly understood. Here, we reported MnO2 nanowires loaded with single atomic Ag (Ag-MnO2) that can simultaneously catalyze oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The incorporation of Ag into the crystal framework of alpha-MnO2 provided multiple benefits including an improved conductivity and a substantial increase in both lattice distortion and oxygen vacancies. As a result, Ag-MnO2 outperformed alpha-MnO2 in oxygen electrocatalysis and showed similar to 3-fold enhancement in kinetic current density. The Zinc air battery containing the Ag-MnO2 displayed a high discharge peak power of 273.2mWcm(-2), an energy density of 915.4 Wh kgZn(-1) and an outstanding rate performance. The Zinc air battery (ZAB) stably operated up to 3200 cycles of charge-discharge. Such excellent rechargeability can be ascribed to the promoted crystal phase transformation from alpha-MnO2 to delta-MnO2 that is beneficial for OER due to the presence of atomic Ag.