CoFe_x-CoFe₂O₄/N-doped carbon nanocomposite derived from in situ pyrolysis of a single source precursor as a superior bifunctional electrocatalyst for water splitting

Application of a bifunctional electrocatalyst for simultaneously producing H₂ and O₂ is still a great challenge, which is important for the enhancement of the overall efficiency of water electrolysis. Taking advantages of the superior conductivity of N-doped graphite carbon, the good electrocatalytic performance of Co-based alloys for HER and excellent performance of cobalt-based oxide for OER, herein, we prepare a CoFe_x-CoFe₂O₄/N-doped carbon nanocomposite with a hierarchical porous structure used to HER and OER by pyrolysis of a new single source precursor {[Co(H₂O)₆][Fe(Hedta)Cl]₂·4H₂O]}. CoFe_x-CoFe₂O₄/N-doped carbon displays high activity with small overpotentials of respective 159 and 257 mV required to achieve a current density of 20 mA cm⁻² as well as catalytic durability for HER and OER in 1.0 M KOH. Furthermore, this bifunctional electrocatalyst enables an alkaline electrolyzer with 20 mA cm⁻² at a cell voltage of ∼1.68 V. The good performance of CF-CFO/NC for HER and OER can be attributed to the low charge transfer impedance, a porous structure and the synergistic role of cobalt-based alloy and cobalt-based mixed metal oxide. This work may provide a new approach to prepare an efficient, cost-effective and superior electrocatalyst in large scale using earth-abundant elements.