Efficient nanointerface hybridization in a nickel/cobalt oxide nanorod bundle structure for urea electrolysis

Urea electrolysis has received great attention for the energy-relevant applications, and efficient nanostructured catalysts are required to overcome the sluggish urea oxidation kinetics. Herein, we noticed that the valence state of Ni in the hybrid Ni/Co oxide nanorods can be correlated to the catalytic capability for urea oxidation. Crystal lattice hybridization was found in the interface of Ni/Co oxide nanoparticles that assembled as a nanorod bundle structure. The more or the less of Ni 2+ /Ni 3+ generated lower catalytic ability, and Ni/Co oxide with the optimum content of Ni 2+ /Ni 3+ exhibited the highest catalytic ability for urea oxidation because of the efficient synergism, resulting from the formation of high valence state of Ni species and improved kinetics. A low onset potential of 1.29 V was required for the urea oxidation compared with the high onset potential of 1.52 V for water oxidation; high selectivity for urea oxidation was found in the potential below 1.50 V, and as a promising application for urea-assisted water electrolysis about 190 mV less was required to provide 10 mA cm −2 in the two-electrode system, indicating the energy-efficient nature for hydrogen evolution. The study provides some novel insights into the Ni/Co catalyst design and fabrication with efficient catalytic synergism for electrocatalysis. Efficient Ni valence state synergism was found active in the electrocatalysis reaction, resulting from the crystal lattice hybridization in the interface of Ni/Co oxide nanoparticles assembled as a nanorod bundle structure.