Linglei Jin,Baikang Zhu,Xuesong Wang,Le Zhang,Debin Song,Jian Guo,Hengcong Tao
With the assistance of surfactant, Fe nanoparticles are supported ong-C3N4nanosheets by a simple one-step calcination strategy. Meanwhile, a layer of amorphous carbon is coated on the surface of Fe nanoparticles during calcination. Transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) were used to characterize the morphology, structure, and composition of the catalysts. By electrochemical evaluate methods, such as linear sweep voltammetry (LSV) and cyclic voltammetry (CV), it can be found that Fe25-N-C-800 (calcinated in 800 °C, Fe loading content is 5.35 wt.%) exhibits excellent oxygen reduction reaction (ORR) activity and selectivity. In 0.1 M KOH (potassium hydroxide solution), compared with the 20 wt.% Pt/C, Fe25-N-C-800 performs larger onset potential (0.925 V versus the reversible hydrogen electrode (RHE)) and half-wave potential (0.864 V vs. RHE) and limits current density (2.90 mA cm−2, at 400 rpm). In 0.1 M HClO4, it also exhibits comparable activity. Furthermore, the Fe25-N-C-800 displays more excellent stability and methanol tolerance than Pt/C. Therefore, due to convenience synthesis strategy and excellent catalytic activity, the Fe25-N-C-800 will adapt to a suitable candidate for non-noble metal ORR catalyst in fuel cells.Keywords:oxygen reduction reaction;iron;coating;P-123
The critical micelle concentration (CMC) is one main parameter of surfactants , so an accurate, rapid, and convenient method for CMC determination is of great significance for surfactant applications. In this paper, three samples of carbon quantum dots (CQDs) with different fluorescence properties were developed as fluorescent probes for the CMC determination of CTAB , SDS , Triton X-100, perfluoro OBS and Pluronics® P-123. The fluorescence excitation and emission spectra of a constant amount of the CQDs in different concentrations of the surfactant solution were recorded, and then the CMC values of the surfactant were deduced from the fluorescence intensity change and the Stokes shift variation. The obtained CMC data using three samples of the CQDs agree well with those in the published literature. It is also demonstrated that in the micellization process the interaction between the CQDs and the surfactant molecules is complicated, because the fluorescence properties of the CQDs are found to be related to the characteristics of the CQDs, the head group type of ionic surfactants , the chemical structure between the hydrophobic and hydrophilic segment, and the chemical nature of the hydrophobic chains of the surfactants. So, the CQDs are demonstrated to be located at the palisade layer in the surfactant micelles due to the surface-attached polar groups on the CQDs although the CQDs are mainly hydrophobic as fluorescent probes. The fluorescent CQDs are considered to be new choices of the fluorescent probes in the facile CMC measurement of the surfactants.
危险品化学品经营许可证（带存储）