Constructing a composite catalyst containing amorphous nickel hydroxide/crystalline lanthanum carbonate hydroxide for urea electrolysis

Abstract

The urea oxidation reaction (UOR) is considered a promising alternative to the anodic slow kinetics oxygen evolution reaction (OER) in water electrolysis due to its lower theoretical potential (0.37 V) compared to OER (1.23 V). To design an efficient catalyst for UOR coupled water electrolysis, in this work, a novel amorphous nickel hydroxide/lanthanum carbonate hydroxide composite catalyst (Ni(OH) 2 /La 2 (CO 3 ) 2 (OH) 2 ) with unique cactus-like morphology was grown on nickel foam (NF) by a one-step hydrothermal strategy. The Ni(OH) 2 /La 2 (CO 3 ) 2 (OH) 2 /NF exhibits a unique cactus-like morphology with 3D hierarchical heterostructures, which could expose more active sites and generate a large number of oxygen vacancies. The electron transfers from Ni to La and the synergistic effect of amorphous/crystalline interface regulate the surface chemical environment of the catalyst, resulting inimproving the electrocatalytic performance in anodic UOR and cathodic hydrogen production. Therefore, the assembled two-electrode system for urea-assisted water electrolysis only required a cell voltage of 1.42 V to achieve a current density of 10 mA cm -2 , which is significantly superior to overall water electrolysis. This work provides a new idea for exploring metal carbonate hydroxides with high activity and stable electrocatalysts for water splitting and other organic electro-oxidation.