Ultrafine-grained NiCo layered double hydroxide nanosheets with abundant active edge sites for highly enhanced electro-oxidation of urea

Abstract Two-dimensional NiCo layered double hydroxide (LDH) was one of the most promising catalysts for urea oxidation reaction (UOR), but its catalytic performance is still far from satisfactory. Structure engineering is an efficient approach to tailoring the quantities of active sites. Herein, ultrafine-grained NiCo LDH nanosheets with partial exfoliation are synthesized by transforming unstable EDTA-intercalated NiCo LDH into stable NiCo-CO32− LDH in 1.0 M KOH. The structure-engineered NiCo LDH nanosheets are near-vertically aligned and thus expose numerous accessible crystal edge sites on the basal plane and edge sites for UOR. In addition, the incorporation of Co helps improve the conductivity and promote the Ni3+/Ni2+ redox reaction. The catalyst materials thus deliver a current density of 10 mA cm−2 at a low potential of 0.341 V vs Hg/HgO, showing a reduction of 123 and ≥ 61 mV in overpotential relative to the nickel hydroxide and common NiCo LDH, respectively. The relationship between the electrochemical properties and the structure was comprehensively studied and revealed.