Self-supported ultrathin NiMn-LDH nanosheets for highly active and robust urea oxidation

Abstract

Due to its low equilibrium potential, urea oxidation reaction (UOR) is an advantageous alternative to the conventional anodic water oxidation reaction (OER) for energy-saving hydrogen production. Developing energy- and time-saving methods to synthesize active and stable UOR catalysts is significant. Herein, we present a simple and time-efficient method for the direct growth of defect-rich few-layered NiMn-layered double hydroxide (NiMn-LDH) nanosheets on nickel foam at ambient temperature and pressure. The defect-rich, few-layered structure exposes numerous active sites, promoting the formation of high-oxidation state Ni species at low overpotentials. Additionally, the introduction of Mn facilitates Ni oxidation and stabilizes in-situ formed NiOOH species. The optimized f-NiMn-LDH catalyst exhibits compelling UOR activity, requiring only 1.310/1.330/1.387 V for 10/100/400 mA cm−2 UOR, respectively. When used directly in urea-assisted hydrogen production, it achieves a low cell voltage of 1.436 V for a high current density of 100 mA cm−2, representing a substantial 249 mV reduction compared to water electrolysis. This work offers a simple strategy for preparing high-performance electrocatalysts for energy-efficient hydrogen production via urea-assisted water splitting.