CoFe nanoalloy particles encapsulated in nitrogen-doped carbon layers as bifunctional oxygen catalyst derived from a Prussian blue analogue

Highly active bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reactions (ORR) have attracted increasing attention in metal-air batteries and fuel cells. CoFe nanoalloy particles encapsulated in nitrogen-doped carbon and nitrogen-doped carbon nanotubes (CoFe@NC-NCNT-H) are synthesized by pyrolyzing a Prussian blue analogue precursor (i.e. Fe-3[Co(CN)(6)](2)) as low as 600 degrees C, and followed by HNO3 treatment. Such low temperature pyrolysis and HNO3 treatment affords the hybrid mesoporous material with a high level of nitrogen content (similar to 10%) and a relatively high specific surface area (similar to 210.5 m(2) g(-1)), capable of providing active sites and mass transport channels. In alkaline solution, CoFe@NC-NCNT-H is highly active towards OER with a low onset potential (similar to 1.35 V) and a small overpotential (similar to 380 mV) to reach 10.0 mA cm(-2), comparable to the state-of-the-art RUO2. CoFe@NC-NCNT-H is also a good ORR catalyst, and more importantly it exhibits an improved stability compared to commercial Pt/C. CoFe@NC-NCNT-H displays promise as a bifunctional catalyst with an extremely low potential difference (similar to 0.87 V between ORR at -3.0 mA cm(-2) and OER at 10.0 mA cm(-2)), superior to commercial Pt/C and RUO2. The facilely prepared CoFe@NC-NCNT-H with high bifunctional performance and stability promises great potential for ORR and OER. (C) 2018 Elsevier B.V. All rights reserved.