Hierarchical porous activated carbon (AC) materials were prepared from a composite of highly accessible carbon sources, sodium alginate and bacterial cellulose, by carbonization and KOH activation. The asobtained carbon materials not only possessed rich oxygenated functionalities but also formed a hierarchical porous structure. The unique structures and chemical compositions of the resulting materials demonstrate good potential for use in supercapacitor electrode materials. The AC had a three-dimensional interconnected network structure consisting of sheet-like connected particles. Interestingly, the carbon material possessed high graphitization degree and good electrical conductivity. The electrochemical properties of electrodes were evaluated in a three-electrode system in 6 M KOH. Due to the synergistic effects of the rich oxygen content and the porous structure, the sample calcined at 700 degrees C showed a high gravimetric capacitance of 302 F/g, an excellent capacitance retention ratio of 75.2% at 10 A g(-1), and good cycling stability with 93.8% capacitance retention after 10,000 cycles. The as-obtained single electrode exhibited a very high energy density of 23.7 W h kg(-1), making it more interesting than commercial AC for practical applications. This study demonstrates that the utilization of abundant polymers from nature is a good route for fabricating high-performance supercapacitor electrode materials. (C) 2018 Elsevier B.V. All rights reserved.