Bifunctional 2D Electrocatalysts of Transition Metal Hydroxide Nanosheet Arrays for Water Splitting and Urea Electrolysis

The replacement of noble-metal-based electrocatalysts with earth-abundant, low-cost bifunctional electrocatalysts for efficient hydrogen generation is required. Herein, an amorphous and porous 2D NiFeCo hydroxide nanosheets grown on nickel foam (NF) (NiFeCo LDH/NF) by a cost-effective electrodeposition method was explored for efficient electrolytic water splitting and urea electrolysis. Experimental results show that porous confinement in 2D orientation, amorphous nature, and synergistic effect leads to the excellent catalytical performance of the as-prepared 2D NiFeCo LDH/NF electrode for overall water splitting and urea electrolysis. The NiFeCo LDH/NF electrode presents promising behavior for water electrolysis with a small overpotential of 210 mV and 108 mV, respectively, is required for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) to gain 10 mA cm–2. More notably, the bifunctional NiFeCo LDH/NF catalyst, for water electrolysis, needs a lower potential of 1.57 V to gain 10 mA cm–2 in 1 KOH. Furthermore, the electrochemical urea oxidation results show that NiFeCo LDH/NF requires just 0.280 V (vs SCE) to drive 10 mA cm–2 in 1 M KOH with a 0.33 M urea, whereas urea-mediated electrolysis cells require a very low potential of 1.49 V at 10 mA cm–2. The present results provide remarkable and notable insights into the preparation of non-noble and highly efficient 2D transition metal hydroxide electrocatalysts with performances that allow them to compete for widespread use in various applications.