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To treat typical organic wastewater efficiently, a novel Fenton-like processes based on ZnO/CuO composite cathode induced by oxygen reduction reaction (ORR) electrocatalysis with enhanced electrocatalytic performance was established successfully. Electrochemical testing investigation indicated that the ZnO/CuO cathode possessed conspicuous redox peak and better conductivity than uncompounded electrodes. Additionally, the removal efficiency of methylene blue and its chemical oxygen demand (COD) reached 96.4% and 70.8% after 120 min, respectively. Next, the feasibility of the material in practical application was also discussed. Subsequently, electrocatalytic principle based on valence state changes of metal elements on the electrode surface were also studied by x-ray photoelectron spectroscopy (XPS). Redox reactions between the active species H2O2 and the species Cu+ promoting Fenton-like processes were deduced. Namely, the conversion of Cu(I) and Cu(II) on the electrode surface was accompanied by OH generation. The combination of ZnO and CuO improved the surface morphology, increasing the active site of ORR and the yield of H2O2, thus greatly enhanced the Fenton-like activity. Finally, the main intermediates were identified by Gas chromatography-mass spectrometer (GC-MS), and possible pathways for dye degradation were proposed. In short, the research of ZnO/CuO cathode provided great significance for heterogeneous Fenton-like degradation and also showed its application potential in water treatment and remediation.

TiO2 nanosheet based flowerlike architectures with a surface area as high as 171 m2 g−1 were prepared through a solvothermal method. The sensing performance of TiO2 nanosheet based flowerlike architectures is enhanced by increasing density of surface unsaturated Ti atoms with dangling bonds through hydrogenation. We proposed a concept of the unsaturated Ti atoms serving as the sensing reaction active sites, and described in detail the sensing mechanism at the atomic and molecular level. The unsaturated Ti atoms not only generate non-contributing (free) electrons and adsorb oxygen molecules, but also catalyze the sensing reaction. In principle, the hydrogenation strategy may be used to improve sensing performances and catalytic activities of other metal oxides. The concept of the unsaturated metal Ti atoms serving as active sites can deepen understanding of the sensing and other catalytic reaction mechanisms, and provides a new insight to the design and fabrication of advanced sensing materials, catalysts and electronic devices.

The search for active semiconductor photocatalysts that can utilize adequately solar-energy remains to be an open issue. CdTe nanoflakes and nanowires with a range of texture coefficients of (111) have been synthesized. Photocatalytic activities of the CdTe nanocrystals in degradation of malachite green, methyl orange, acid red 88 and ciprofloxacin can be enhanced by increasing the texture coefficients of (111) and reducing texture coefficient of (220). The exposed polar {111} facets were found to be the active facets, and a charge separation model between polar Cd-CdTe (111) and Te-CdTe ( 1 ¯ 1 ¯ 1 ¯ ) surfaces is proposed. An internal electric field is created between polar Cd-CdTe (111) and Te-CdTe ( 1 ¯ 1 ¯ 1 ¯ ) surfaces by the spontaneous polarization, and the internal electric field drives separation of the photoinduced electrons and holes. Therefore, the CdTe nanoflakes with exposed polar {111} facets synthesized by using oleylamine as a morphology controlling agent show superior photocatalytic activity, compared with CdTe nanowires, nanocrystals with irregular shapes and commercial powders as well as CdS branched nanostructures. The charge separation model provides a clear opinion into charge transfer in the semiconductor nanocrystals with exposed active facets, and affords guidance to design more effective photocatalysts, solar cells and other photoelectronic devices.

Novel Ti/Sb2O3–SnO2/Er–PbO2 anodes were fabricated based on doping Er ions into the PbO2 crystal and enhanced electrocatalytic degradation efficiency for organic pollutants was achieved successfully. The doping principle, possible degradation pathway of methylene blue and electrocatalytic mechanism have been discussed in depth. Based on the comprehensive analysis of crystal parameters by X-ray diffraction (XRD) results and typical formulas, the doping principle was confirmed to be the partial substitution of Pb ions by Er ions in PbO2 nanocrystal and might form point defects. Additionally, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) investigation indicated that the Ti/Sb2O3–SnO2/Er–PbO2 anodes possessed higher oxygen overpotential and better conductivity than undoped electrodes. The optimum conditions for the degradation of methylene blue were obtained via studying the effects of different parameters, such as electrolyte concentration (0.01–0.4 M Na2SO4), current density (20–60 mA cm−2), initial methylene blue concentration (10–70 mg L−1) and initial pH (3–11). At the optimum conditions, the total organic carbon (TOC), the decolorization rate constant (kdec) and the energy consumption (EC) reached up to 65.34%, 0.036 min−1 and 0.08 (kWh(gTOC))−1, respectively. Moreover, the electrocatalytic degradation mechanism of the Ti/Sb2O3–SnO2/Er–PbO2 anodes to methylene blue was proposed to be that, the presence of point defects induced an increase of electron transport tunnels, and promoted the production of more hydroxyl radicals ( OH) and SO4 -. The possible electrocatalytic mineralization pathway of methylene blue at Ti/Sb2O3–SnO2/Er–PbO2 anodes was also speculated by UV–visible absorption spectroscopy, gas chromatography combined with mass spectrometry (GC-MS) and liquid chromatography combined with mass spectrometer (LC-MS). This work will provide significant references for exploring the mechanism between doped electrodes materials and electrocatalytic degradation performance.

NiSe ultralong nanobelts were synthesized by a solvothermal reaction of Ni with Se and KBH4 in ethylenediamine and subsequent annealing in Ar. The aspect ratios of NiSe ultralong nanobelts can be tuned by altering the reaction time. The adsorption performance of NiSe nanostructures with different aspect ratios was investigated, and the as-obtained NiSe ultralong nanobelts exhibited excellent adsorption capability of malachite green in wastewater, which could be attributed to their unique honeycomb-like assembly and high surface area. The adsorption process agreed well with the pseudo-second-order kinetics and the Langmuir isotherm equation. Thermodynamic parameters indicated that the adsorbent processes were spontaneous. Electrostatic attraction between malachite green and NiSe ultralong nanobelts was considered as the adsorption mechanism. The NiSe ultralong nanobelts could be regarded as a promising adsorbent for the removal of MG in wastewaters.

The 3-dimensional hierarchical ZnO flower-like architectures have been synthesized in a Zn(Ac)2·2H2O-Na2SeO3-KBH4-pyridine solvothermal system at 100°C for 24h. The flower-like architecture is assembled from ZnO nanosheets with a thickness of ∼1.5nm, and the flower-like architecture specific surface area is 132m(2)/g. When the ZnO flower-like architecture is used as the adsorbent for acid fuschin (AF), malachite green (MG), basic fuchsin (BF), congo red (CR) and acid red (AR) in water, the adsorption capacities for AF, MG, BF, CR and AR are 7154.9, 2587.0, 1377.9, 85.0 and 38.0mg/g, respectively. Evidently, the as-obtained ZnO flower-like architectures show excellent adsorption performances for triphenylmethane dyes, and the adsorption capacity of 7154.9mg/g for AF is the highest of all adsorbents for dyes. The adsorption mechanism can be attributed to the electrostatic attraction and the formation of ion-association complex between triphenylmethane dyes and ZnO hierarchical flower-like architectures.