Two-dimensional hetero-nanostructured electrocatalyst of Ni/NiFe-layered double oxide for highly efficient hydrogen evolution reaction in alkaline medium

High-performance, cost-effective and stable electrocatalysts are critical for hydrogen evolution reaction (HER) via water splitting in alkaline media. Herein a unique hetero-nanostructured Ni/NiFe-layered double oxide (Ni/NiFe-LDO) on Ni foam (NF) has been successfully constructed through phase-transition and controlled in-situ reduction process. Because the two-dimensional (2D) morphology of NiFe-LDO nanosheets can stabilize uniform in-situ formed nano-Ni sites, the prepared Ni/NiFe-LDO on NF displays a high catalytic activity for HER in 1.0 M KOH solution, which requires an extremely low overpotential of 29 mV to afford a current density at 10 mA cm(-2), achieves a Tafel slope of 82 mV dec(-1) and maintains an excellent stability of electrolysis for at least 24 h. Detail characterizations reveal that the synergistic effect between nano-Ni and NiFe-LDO nanosheets contributes to the prominent HER activity. In NiFe-LDO, Fe2O3 facilitates the adsorption of H2O on the interface region of Ni-Fe2O3, which is beneficial for water activation, then NiO offers the active sites for hydroxyl adsorption (*OH), meanwhile nano-Ni sites are active to adsorb hydrogen intermediates (H*). All of the above accelerates the water dissociation in Volmer-step reaction.