Efficient oxygen reduction and evolution on 3D Fe/N co-doped carbon nanosheet-nanotube composites with carbonaceous heterostructure via in-situ growth of carbon nanotubes

Non-precious metal electrocatalysts exhibiting high activity and durability for both oxygen reduction (ORR) and oxygen evolution (OER) are required for metal-air batteries. Herein, in-situ growing carbon nanotubes (CNTs) on polyvinyl pyrrolidone derived carbon nanosheets is utilized to obtain 3D hierarchical structured Fe/N co-doped Fe/PVP-M catalyst. Benefiting from the in-situ growth of CNTs, carbonaceous heterostructure is obtained at the interface and enhances the conductivity. More meso-/macro-pores are formed to facilitate the O-2 transportation. High contents of pyridinic-N, Fe-N-x, graphitic-N, and Fe3C are gained. These exclusive structural features provide Fe/PVP-M attractive activity for both ORR and OER in alkaline electrolyte, i. e., high onset potential (1.008 V at current density -0.1 mA cm(-2)) and low Tafel slope (86.2 mV dec(-1)) for ORR, and low onset potential (1.43 V) and low Tafel slope for OER. Excellent stability of the hierarchical structure during measurements indicates the promising potential of this 3D structured Fe/N/C catalyst for metal-air batteries.