N-doped hierarchically porous carbon based on MnO₂ nanotubes as self-sacrificial reaction templates for supercapacitors and oxygen reduction

In this work, N-doped hierarchically porous carbon (PDHC) has been prepared when MnO₂ nanotube and polyaniline are selected as self-sacrificial reaction template and carbon source, respectively. Benefiting from the suitable N-doping degree inherited from polyaniline, and the hierarchical porous structure originated from the synergistic adjustment of self-sacrificial template and activation treatment, PDHC exhibits significant advantages for electrochemical energy storage. Typically, the PDHC has the high specific capacitance (467 F g⁻¹ at 1 A g⁻¹) and rate performance (71.9% capacitance retention at 20 A g⁻¹) in three-electrode systems. PDHC-based coin type symmetric supercapacitors are assembled with 1 M H₂SO₄ electrolytes and ionic liquid electrolytes, respectively, and they all exhibit a considerable synergistic power-energy output (752 W kg⁻¹ at 31.1 Wh kg⁻¹ and 750 W kg⁻¹ at 74.8 Wh kg⁻¹) and an acceptable cycling stability (6.5% and 13.9% loss over 5000 cycles). Meanwhile, the electrocatalytic performance of PDHC towards oxygen reduction reaction is also investigated, where a superior catalytic activity and a outstanding durability via 4e^- pathway in the alkaline solution are confirmed, heralding the possibility of its practical application in fuel cells.