Tuning lattice defects to facilitate the catalytic performance of Ni–Cu–O hybrid nanoparticles towards methane oxidation

Herein, an attempt was made to modulate the properties of NiO oxides towards methane combustion. For this purpose, appropriate content of copper was introduced into the NiO lattice to generate Cu–Ni solid solution, in view of the similarities in atomic-size and electronegativity between copper and nickel. This delivered more unsaturated nickel atoms and reduced the nanoparticle size of NiO, generating more lattice defects. Also, the oxygen binding energy was significantly lowered stemming from the creation of Ni–O–Cu linkage, and the interaction between CuO and NiO. Consequently, larger amount of active surface adsorbed oxygen sites were given and the reducibility of NiO was considerably enhanced for bimetallic systems compared with pure NiO. Meanwhile, the surface acid-base properties were adjusted over samples after the addition of copper, attributed to the charge redistribution among the oxygen and metal atoms. These effects accounted for the preferred activity, water-resistance, and durability for Cu-promoted NiO catalysts.