Urea-assisted hydrogen production: insights into Ni(Co, Mn) LDH-based multifunctional electrocatalysts

Abstract

The pursuit of sustainable energy technologies has sparked significant interest in multifunctional, transition metal-based nanostructured electrocatalysts for efficient energy conversion. A promising pathway toward energy sustainability involves hydrogen production through hybrid water electrolysis. By tackling the slow kinetics of the oxygen evolution reaction (OER), integrating urea electrolysis significantly lowers the cell voltage, offering a promising energy-saving route to hydrogen production. In this work, Ni-based layered double hydroxide (LDH) nanostructures exhibit remarkable stability in alkaline media, positioning them as versatile electrocatalysts for the urea oxidation reaction (UOR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Using a facile one-pot co-precipitation method, NiCo-LDH and NiMn-LDH nanostructures are synthesized. Interestingly, for the HER and UOR, these nanostructures show relatively small overpotentials of 360 and 90 mV at 50 mA cm⁻², respectively. Furthermore, NiCo-LDH/NF electrodes are used as the anode and cathode in hybrid water electrolysis, which is accomplished at a lower cell voltage of 1.66 V at 10 mA cm⁻². The numerous active sites in the LDH nanostructures and the extremely conductive nickel foam substrate work in sync to produce this exceptional electrocatalytic performance. Overall, this work suggests a robust idea for implementing efficient, durable, and multifunctional electrocatalysts that enhance the HER, OER, and UOR, contributing to next-generation hydrogen production technologies.