Ag nanoparticle-modified MnO2 nanorods catalyst for use as an air electrode in zinc–air battery

In this paper, we report the synthesis, characterization and application of an inexpensive yet efficient bifunctional catalyst composed of Ag nanocrystals (∼11 nm) anchored on α-MnO2 nanorods. The nanostructured Ag–MnO2 catalysts exhibit improved oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance in aqueous alkaline media, in terms of onset potential, generated current density and Tafel slopes. Rotating disk electrode results show that near-four electrons per oxygen molecule were transferred during ORR of Ag–MnO2. A zinc–air battery prototype employing Ag–MnO2 in the air electrode was successfully operated for 270 cycles under light discharge–charge condition. Ag–MnO2 is an efficient bifunctional catalyst for electrochemical devices such as metal–air batteries and alkaline fuel cells.