LAUSR

Low‐cost and high‐activity electrocatalysts for the oxygen reduction reaction (ORR) are necessary for the development of fuel cells and metal‐air batteries. Manganese oxide would be a good candidate because of its low cost, abundant supply, and environmental benignity if not for its relatively low activity compared with noble metals. To improve the ORR activity of manganese oxide, we developed a sulfurization process to create pores in 2 D manganese oxide nanosheets. The nanoporous MnO2 nanosheets (np‐MnO2‐ns) prepared as such contain 7 nm pores in the nanosheets and their half‐wave potential (0.73 V) is 40 mV more positive than that of pore‐free MnO2 nanosheets (0.69 V). The higher ORR activity of np‐MnO2‐ns may be attributed to the combination of a large surface area and the presence of high‐ORR‐activity Mn3+/4+ sites. The np‐MnO2‐ns also showed an enhanced oxygen evolution reaction activity and delivered a good performance in rechargeable Zn‐air batteries.