Material Design of Bimetallic Catalysts on Nanofibers for Highly Efficient Catalytic Reduction of 4-Nitrophenol.

In this study, CuO-TiO nanofiber catalysts were fabricated by an electrospinning process, followed by thermal annealing at various temperatures ranging from 300 to 700 °C. The phase transformation from CuO to metallic Cu was carried out through immersion treatment in NaBH solution. The resulting CuO-TiO and Cu-CuO-TiO nanofibrous mats were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. The results revealed that the crystalline phase composition of the nanofibrous mats considerably affected the efficiency of photocatalytic reduction, where the CuO-TiO catalysts with a predominant anatase content was found to be more photoactive than the rutile phase. Similarly, the presence of both Cu and CuO species was more beneficial for promoting the activity of fibers by acting as an interim location for facilitating the electron transfer. The fabricated Cu-CuO-TiO nanofibrous mat with a ratio presented high conversion (∼99%) within several minutes with the apparent pseudo-first-order rate constant of 0.42 and 0.50 min in the absence and presence of UV light irradiation as well as excellent stability in recycling runs with a stable conversion efficiency of 97% or higher over five successive catalytic cycles.