Potassium-oxygen batteries (KOBs) are a promising energy storage technology with high theoretical en-ergy density, low overpotential and long cycle life. Cathode microstructure plays a significant role in the electrochemical performance of KOB. In this article, hierarchical porosity was introduced to commer-cially available carbon paper cathodes by the thermal pretreatment in air at different pretreatment times. This pretreatment modifies the properties, such as, surface area, defects, oxygen functional groups etc. and it has been found to enhance the discharge capacity and it result in reduction of dis-charge overpotentials.