In situ grown 3D hierarchical MnCo2O4.5@Ni(OH)2 nanosheet arrays on Ni foam for efficient electrocatalytic urea oxidation.

• The triple-layered heterostructure provides abundant active sites for urea electrooxidation. • The synergistic effect between MnCo 2 O 4.5 and Ni(OH) 2 promotes the electrooxidation of urea. • The as-prepared MnCo 2 O 4.5 @Ni(OH) 2 /NF exhibits much better stability and activity towards urea electrooxidation. Urea oxidation reaction (UOR) is considered as a prospective technology for hydrogen generation and degradation of urea-rich wastewater concurrently. In theory, nickel-based catalysts exhibit superior activity in this regard. However, the intrinsically low conductivity and limited active sites on usual nickel-based catalysts impede their applications in UOR. Hence, a hierarchical triple-layered heterostructure, which consists of MnCo 2 O 4.5 nanosheets seamlessly sandwiched between a bottom layer of Ni foam substrate and a top layer of Ni(OH) 2 nanosheets, are directly synthesized via a successive hydrothermal-calcination-hydrothermal process (MnCo 2 O 4.5 @Ni(OH) 2 /NF). Taking advantages of the distinctive sandwich structure and the synergistic effect between MnCo 2 O 4.5 and Ni(OH) 2 , the resulting MnCo 2 O 4.5 @Ni(OH) 2 /NF electrode presents superior electrocatalytic activity with a small onset potential of 0.19 V versus Ag/AgCl as well as a current density of 650 mA cm−2 in 5 M KOH and 0.33 M urea electrolyte. This work provides a promising platform for designing an effective hybrid material toward a wide range of electrochemical applications. [ABSTRACT FROM AUTHOR]