Efficient oxygen evolution catalysts with synergistic reactivity: CoFe2O4/C derived from bimetallic organic framework supported on nitrogen-doped carbon nanoarray structure

Abstract

Here, we covered a polyaniline nanowire array (denoted as PANI) on carbon paper (denoted as CP) by a electrochemical polymerization method, directly grown MOF-74-Co/Fe on its surface and pyrolyzed to form the CoFe2O4/C supported on nitrogen-doped carbon nanoarray materials (denoted as NC-CoFe2O4/C@CP), which is prepared a highly active and stable OER catalyst. PANI can not only be used as a “binder”, grow MOF on its surface and cover the carbon paper, but also improve the conductivity and stability of the material by forming nitrogen-doped carbon after pyrolysis. And its unique 3D nano-array structure not only greatly increases the surface area, but also provides more attachment sites for CoFe2O4, thereby accelerating electron transport and improving OER performance. High specific surface area, high utilization of the catalyst, enhanced electron transport characteristics and retention characteristics of the original carbon paper characteristics ensure excellent OER activity. The final sample exhibits outstanding activity for OER in alkaline solution, accompanied by a low onset potential about 1.52 V (vs reversible hydrogen electrode), and the small Tafel slope of 70 mV dec−1. In particular, after 21600s, the current drop is negligible, which is means that the NC-CoFe2O4/C@CP catalyst has the high stability. Density Functional Theory (DFT) calculation reveals the main surface adsorbent of CoFe2O4 is OH*, and the surface Co atoms are the main active sites.