Multifunctional characteristics of a one-dimensional bimetallic oxyhydroxide nanorod-coupled polyaniline interface for accelerated water and urea electrolysis

Abstract

Designing an efficient and multifunctional electrocatalyst is central to hydrogen production technologies for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and urea oxidation reaction (UOR). Herein, we report the synthesis of nickel cobalt oxyhydroxide nanorods interfacially coupled with polyaniline-functionalized carbon fibers (NiCoOOH@PANi-CF) as a trifunctional electrocatalyst for the HER, OER, and UOR. The NiCoOOH catalyst with oxygen vacancies effectively catalyzed these reactions, while the one-dimensional nanorods ruptured the gas bubbles accumulated on the catalyst's surface. Density functional theory calculations suggested that the PANi layers captured intermediate H⁺ ions/CO₂ molecules and suppressed the recombination reactions. Owing to these multifunctional properties, the NiCoOOH@PANi-CF electrocatalyst demonstrated low HER overpotentials of 35, 30, and 110 mV (at 10 mA cm⁻²) in acidic, alkaline, and neutral electrolytes, respectively. Furthermore, the interfacially coupled electrocatalyst exhibited outstanding durability for the HER, OER, and UOR. Post-catalysis assessment revealed that the PANi layers effectively coupled with the NiCoOOH catalyst and prevented catalyst delamination from the substrate. Urea electrolysis exhibited a full cell voltage of 1.39 V (at 10 mA cm⁻²), while water electrolysis showed a cell voltage of 1.51 V (at 10 mA cm⁻²), both results surpassing those of the most promising catalysts previously reported. This work demonstrates an innovative catalyst design possessing multifunctional properties to accelerate catalyst efficiency and durability.