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

Abstract

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 Fe 3 C 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 À 0.1 mA cm À 2 ) and low Tafel slope (86.2 mV dec À 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.

Three-Dimensional Fe Single-Atom Catalyst for High-Performance Cathode of Zn–Air Batteries

“…Herein, 3D SAFe with high specific surface area and open-pore structure were massively produced assisted by NaCl template utilizing a freeze-drying and in situ pyrolysis technique. − Concretely, the metal and carbon precursors are distributed uniformly throughout the boundaries of NaCl grains during the freeze-drying process and the open pores formed after pyrolysis and template removal, which promotes mass transportation and increases the amount of effective Fe–N 4 sites. The obtained 3D SAFe exhibits extraordinary ORR electrocatalytic activity with a high half-wave potential of 0.90 V (all potentials are versus RHE) in 0.1 M KOH, which is higher than that of state-of-art Pt/C and most of the reported SACs. − Besides, 3D SAFe exhibits significantly boosted diffusion limiting current density and half-wave potential, higher than that of the Fe SACs with bulk carbon (denoted as Fe-BC)/two-dimensional graphene (denoted as Fe-rGO) supports, confirming that the three-dimensional open-pore structure facilitates the mass diffusion and thus enhances the ORR performance. Moreover, the aqueous Zn–air battery assembled with the 3D SAFe performs satisfactorily with a high peak power density (156 mW cm –2 ) and outstanding durability (80 h).…”

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets

“…Carbon nitride (C 3 N 4 ) has gained significant interest as a photocatalyst in the field of pollutant degradation and hydrogen production due to its visible photoactivity and other outstanding properties [ 33 , 34 , 35 , 36 ]. C 3 N 4 is a metal-free semiconductor that possesses visible absorption, has a layered structure, shows great thermal and chemical stability, and features low-cost and easy synthesis [ 37 , 38 , 39 ]. Its band gap (2.7 eV) and valence and conduction band edges (1.3 eV and −1.4 eV versus standard hydrogen electrode (NHE), respectively) make it suitable for water splitting, degradation of organic pollutants, and CO 2 reduction [ 40 , 41 ].…”