Multielectronic synergetic Hf-doped NiFe-LDH/NF for efficient bifunctional electrocatalytic OER/UOR

The inefficient Ni/Fe ion utilization and poor electrical conductivity of nickel-iron layered double hydroxide (NiFe-LDH) restricts to its development in electrocatalytic oxygen evolution reaction/urea oxidation reaction (OER/UOR). Herein, self-supported Hf-doped NiFe-LDH nanosheet arrays were successfully prepared on nickel foam (Hf-NiFe-LDH/NF) via a one-step solvothermal approach for the first time, in which the introduced high-valent Hf4+ altered the structure of electrons and chemical environment of the atoms and promoted the production of more active sites, thus realizing the fast kinetics of electron transfer on the layer. Meanwhile, the doped metal Hf ions increased the electric conduction and recycling stability of the catalyst. Astoundingly, the overpotential of Hf-NiFe-LDH/NF is barely 258 mV at a current density of 100 mA cm−2, which is 61 mV lower than that of NiFe-LDH/NF, as well as outstanding stability for over 90 h during the OER. Similarly, the potential is only 1.37 V at 100 mA cm−2 during the UOR, 118 mV less was than at OER. Notably, Hf-NiFe-LDH/NF electrocatalyst exceeds the most previously reported electrocatalysts in terms of performance. This study highlights the benefits of Hf doping strategy in electrocatalytic OER/UOR and presents a promising new type of catalyst for future research.