Abstract
The photocatalytic activity of silver-based catalysts containing different amounts of molybdenum disulfide (MoS2; 5, 10 and 20 wt.%) was evaluated by the degradation of the antibiotic ciprofloxacin and the production of hydrogen via water splitting. All the silver (Ag)-based catalysts degraded more than 70% of the antibiotic in 60 min. The catalyst that exhibited the best result was 5%Ag@TiO2-P25-5%MoS2, with ca. 91% of degradation. The control experiments and stability tests showed that photocatalysis was the degradation pathway and the selected silver-based catalysts were stable after seven cycles, with less than 2% loss of efficiency per cycle and less than 7% after seven cycles. The catalyst with the highest hydrogen production was 5%Ag@TiO2 NWs-20%MoS2, 1792 μmol/hg, at a wavelength of 400 nm. This amount was ca. 32 times greater than that obtained by the pristine titanium oxide nanowires catalyst. The enhancement was attributed to the high surface area of the catalysts, along with the synergism created by the silver nanoparticles and MoS2. All the catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) surface area analysis and energy dispersive X-ray spectroscopy (EDS).
Highlights
Industrial development, together with energy shortages and overpopulation of the planet, is perhaps among the most relevant factors affecting the environment and the future sustainable development of society [1–7]
At a higher magnification (Figure 1c) it can be noticed that the nanowires have a square-like form with different ddoommaaiinnss aannddssiizzeess..AABBEETTaannaalylyssisis(s(seeeeTTabalbele1)1f)ofuonudndthtahtatthtehneannaonwoiwreisrehsadhaadhaighhigsuhrsfaucrefoafc4e0o3fm4023g−m1,2gw−1h, iwchhiccahncbaenebxepleaxipneladinbeydthbey hthigehhlyigbhrlaynbcrhaendchsterducsttururecstuorfetsheofwthireesw
The crystalline phase of the catalysts was studied by X-ray diffraction (XRD), using a Bruker D8 Advance X-Ray diffractometer operating at 40 kV and 40 mA (Billerica, MA, USA) and Raman spectroscopy (DXR Thermo Raman Microscope, 532 nm laser source at 5 mW power with a resolution of 5 cm−1 (Waltham, MA, USA)
Summary
Industrial development, together with energy shortages and overpopulation of the planet, is perhaps among the most relevant factors affecting the environment and the future sustainable development of society [1–7]. There are different experimental procedures that allow for synthesizing MoS2 in a simple way, its use is certainly limited by the intrinsic semiconductor behavior and the number of active sites [4,6,19] To improve this behavior, and in the same way that has been addressed with TiO2, different strategies have been developed to modify morphology, specific surface and even the presence of structural defects induced by metal doping (e.g., Pt, Cr, Mn, V) [1,7,11]. In the case of two-dimensional materials such as MoS2, the different synthesis procedures produce crystals formed by the adhesion of a large number of layers [20] Opening these 2D materials is an effective way to alter the physical and chemical properties, such as the conductivity or band gap and, its catalytic activity [3,20]. To the best of our knowledge, the hybrid materials prepared in this research are novel and, as is described later, they can be used efficiently in catalytic environmental decontamination processes and in photocatalytic hydrogen production by water splitting
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