3D self-supporting nickel sponge substrate derived CoFeLDH/SN as an efficient bifunctional electrocatalyst for overall water splitting

The design and fabrication of high-efficiency and low-cost bifunctional catalysts in overall water splitting is crucial for the industrial application of green and clean hydrogen energy. Herein, a three-dimensional (3D) self-supporting nickel sponge (SN) with many nickel synapses prepared by hydrothermal method was employed as the substrate. 2D CoFeLDH nanosheets were grown on nano-Ni synapses of SN by electrodeposition method. For comparison, CoFeLDH also was deposited on a nickel foam (NF) substrate using the same deposition process. The as-prepared CoFeLDH/SN exhibited excellent electrocatalytic performances with 208 mV at 10 mA cm ⁻² for OER and 63 mV at 10 mA cm ⁻² for HER in 1 M KOH alkaline solution, which is better than that of CoFeLDH/NF (276 mV at 10 mA cm ⁻² for OER, and 173 mV at 10 mA cm ⁻² for HER). The electrolytic cell using CoFeLDH/SN as both cathode and anode achieves a voltage of 1.52 V at current density of 10 mA cm ⁻², which is better than that of most previously reported bifunctional catalysts. Our work provides a facile and inexpensive option for the design of bifunctional catalysts in overall water splitting.