SILAR-synthesized ultrathin Ni(OH)2 nanoflakes for urea electrocatalysis: Effect of reaction temperature

초록

Urea electrocatalysis has evolved as a promising strategy that simultaneously addresses two important challenges: wastewater remediation and sustainable hydrogen (H2) production. However, the urea oxidation reaction (UOR) has sluggish reaction kinetics, places significant demands on electrocatalyst design. In this study, ultrathin Ni(OH)2 nanoflakes were synthesized on a conducting stainless-steel (SS) substrate using the intermittent growth process, i.e., SILAR. Reaction temperature-regulated intermittent cationic treatment in an anionic bath allows precise control over the kinetics of the reaction, facilitating the growth of a robust interconnected nanoflake framework. The interconnected nanoflake architecture offers a high density of electrochemically accessible active sites, enables rapid electron transport and enhances electrolyte penetration and reactant diffusion, thereby enhancing UOR kinetics. Furthermore, optimizing the reaction temperature preserves a high concentration of Ni2+ species, which readily transform into electroactive Ni3+ species under anodic polarization, contributing to enhanced catalytic activity. The optimized Ni(OH)2 electrocatalyst delivered 10 mA cm−2 current density at 1.44 (V vs. RHE) and exhibited a lower Tafel slope of 75.81 mV dec−1, indicating favorable reaction kinetics. The improved electrochemical activity is ascribed to the increased density of Ni2+ sites (1.15 × 1017) and an ECSA of 4.37 cm2. In addition, the low onset oxidation potential with 99 % retention after 24 h of stability confirmed the excellent electrocatalytic behavior of the ultrathin nanoflakes toward urea oxidation. © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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