Effect of Ni Incorporation into Malachite Precursors on the Catalytic Properties of the Resulting Nanostructured CuO/NiO Catalysts

Abstract

AbstractSynthetic nickelian malachite nanopowders (Cu1–xNix)2(OH)2CO3 with x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1 were prepared by constant‐pH coprecipitation. N2 sorption isotherms confirmed a steady increase of the BET surface area with increasing Ni content for the as‐synthesized and calcined mesoporous materials. Powder XRD patterns for x ≤ 0.1 indicate the formation of single‐phase materials with an anisotropic contraction of the unit cell. This is related to the gradual decrease of the Jahn–Teller distortion in the malachite structure. An XRD‐amorphous hydroxide‐rich phase is formed for x > 0.1, which appears as spongelike regions in SEM images. Thermogravimetric analysis showed that nickel lowers the onset of thermal decomposition. Powder XRD patterns of the calcined samples evidence the formation of a tenorite structure despite the presence of Ni. Heterogeneous Fenton‐like decomposition of Bismarck Brown Y with H2O2 showed that a Cu/Ni ratio of 92:8 in the nanostructured oxide leads to the highest reaction rate constant derived from a pseudo‐first‐order kinetic rate law expression. Temperature‐programmed CO oxidation experiments revealed that pure CuO achieved the highest activity. Similar performance was observed for the binary system obtained through calcination of the precursor prepared with a Cu/Ni ratio of 96:4.