Enhanced electrocatalytic activity of a layered triple hydroxide (LTH) by modulating the electronic structure and active sites for efficient and stable urea electrolysis

Abstract

A clean and sustainable "hydrogen-based economy"will usher in a new era. Therefore, the hydrogen production pathway is crucial. The urea (CO(NH2)2) electrolysis has recently been investigated as a promising energy-saving approach for renewable hydrogen production compared to conventional water (H2O) electrolysis. This is because of the minimal cell voltage, mitigation of urea-rich wastewater, and availability of electrocatalysts. Herein, we report trimetallic nickel-cobalt-iron layered triple hydroxide nanosheets (NiCoFe-LTH) grown on nickel foam (NF) via a one-step hydrothermal synthesis method. They were tested as catalysts for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) in direct urea fuel cells (DUFCs). NiCoFe-LTH/NF behaves as a highly active durable 2D catalyst electrode for the UOR and HER with the required potentials of 1.337 V and 180 mV to achieve catalytic current densities of 25 and 10 mA cm-2 respectively, in 1 M KOH with 0.33 M urea. Moreover, this electrode also performs well in urea-electrolysis, requiring a very small potential of 1.49 V to achieve 10 mA cm-2 over a period of 30 h. The developed urea electrolyzer is very effective at producing H2. It is cost-effective and involves no difficulties in material synthesis or electrolyzer fabrication, paving the way for the development of clean renewable energy infrastructure.