Modulating the electronic structure of CoFeCNO 2D nanosheets via Ni incorporation for efficient electrochemical oxygen evolution

•The prepared polymetallic CN materials come from a wide range of sources.•The CoFeNiCNO material requires only overpotential of 290 mV to achieve a current density of 10 mA cm−2 and exhibits long-term durability.•All metal elements are uniformly distributed in the interior and surface of the material by electron microscopy.