Hierarchical porous carbon derived from Gardenia jasminoides Ellis flowers for high performance supercapacitor

•Hierarchical porous carbon was prepared from the flowers of Gardenia jasminoides Ellis.•The carbonization, hydrothermal and chemical activation are efficient approaches to convert biomass waste to hierarchical porous carbon.•The porous carbon activated at 800 °C shows optimal electrochemical performance.•The carbon-based supercapacitor has high specific capacitance and excellent durability.