Philippine natural zeolite surface engineered with CuO nanowires via a one-step thermal decomposition route

Abstract

Novel CuO nanowire-zeolite composite was successfully fabricated through facile thermal decomposition of CuSO4 • 5H2O as the lone precursor. The natural zeolites have porous and plate-like structures, which suggest the presence of clinoptilolite-heulandite family of zeolites. After annealing of Cu-exchanged zeolite at 550 °C, CuO nanowires were synthesized with a mean diameter of 80 nm and length of 1.5 μm. XRD analysis revealed that the samples annealed at 550 °C showed clinoptilolite-heulandite peaks, as well as a broad CuO peak. Annealing at a higher temperature of 800 °C led to the amorphization of the zeolite peaks. The XPS spectra of the zeolite with Cu annealed at 400, 550, and 800 °C confirmed that annealing at 550 °C preferably forms CuO rather than Cu2O on zeolite surface. These analyses identified that annealing at 550 °C functionalized the Cu-exchanged zeolite surface, which is desirable for a wide variety of applications such as catalysis, sorbents for environmental applications, and gas sensors.