Engineering superhydrophilic/superaerophobic hierarchical structures of Co-CH@NiFe-LDH/NF to boost the oxygen evolution reaction

3D superhydrophilic/superaerophobic hierarchical "rod-sheet" structure of NiFe-based layered double hydroxides coupled with cobalt carbonate hydroxide (Co-CH@NiFe-LDH/NF) has been synthesized on Ni foam by a Fe3+ ion hydrolysis-induced etching-growth approach under hydrothermal conditions. The Co-CH@NiFe-LDH/ NF electrode demonstrates excellent oxygen evolution reaction (OER) performances, which mainly result from the synergic effect between Co-CH and NiFe-LDH. The unique stepped hierarchical "rod-sheet" structure of CoCH@NiFe-LDH/NF not only benefits the inherent catalytic activity, but also enhances the electron transfer and increases the exposed active sites. Moreover, the superhydrophilic/superaerophobic joint properties of CoCH@NiFe-LDH/NF promote the diffusion of aqueous electrolyte and ensure the rapid release of bubbles. Furthermore, a water-splitting device has been assembled with commercial Pt/C/NF and Co-CH@NiFe-LDH/NF as cathode and anode, respectively, which can work stably for 200 h without obvious degradation. Hence, the strategy of engineering stepped hierarchical structures with synergistic effect may offer a new pathway to synthesizing highly efficient OER electrocatalysts.