Sponge like M-doped Ni/NiO (M = Cu, Co) composites and their catalytic activity toward dye reduction

Sponge like Ni/NiO composites (pristine or doped with Cu or Co) were synthesized using a facile complex decomposition method and utilized as dye reduction catalysts in the presence of sodium borohydride as reductive agent. Ethylenediamine and metal nitrates along with ethanol are the only reagents used and calcination can be performed in air atmosphere at temperatures as low as 300 degrees C. Powder X-ray diffraction patterns revealed that the samples consist of a mixture of metallic and oxide phases in terms of both nickel and dopant (Cu or Co). Obtained pores are in micrometre scale and pore-formation mechanisms based on plausible routes were postulated. Field-emission scanning electron microscopy and energy dispersive spectra were used to investigate the microstructural features as well as the chemical compositions of the complex and calcined samples. Catalytic reduction of methylene blue with NaBH4 was chosen as an environmental reaction which can be monitored by time dependent UV-vis spectroscopy and the composite samples were put to test in order to investigate in terms of activity and robustness. The optimized sample was able to decolorize 97 percent of the dye after 370 s and retained its activity even after 5 consecutive reaction runs without re-generation protocols.