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[en] Highlights: • Activated semi-coke supported TiO_2-rGO photocatalysts were fabricated by one-step solvothermal method. • The photocatalytic performance for NO removal was studied under visible light irradiation. • The introduction of rGO is responsible for superior photocatalytic activity. • Optimum operational parameters at 70 °C, with 8% O_2 and 8% relative humidity were obtained. • Thermal vapor regeneration is the most suitable generation method. - Abstract: The photocatalysts of activated semi-coke supported TiO_2-rGO nanocomposite (TiO_2-rGO/ASC) with different contents of reduced graphene oxide were fabricated by one-step solvothermal method for NO removal under visible light irradiation. It was confirmed that 8% content of reduced graphene oxide presented the best NO photooxidation performance under visible light irradiation at 70 °C with 350–400 mg/m"3 NO,5% O_2 and 5% relative humidity. The reasons for improved activity were discussed, alloyed with the mechanism of producing CO. Detailed structural information of TiO_2-rGO/ASC photocatalysts was characterized by scanning electron microscope (SEM), energy dispersive X-ray Spectroscopy (EDX), X-ray diffraction analysis (XRD), UV–Vis diffuse reflectance spectra (UV–Vis DRS) and photoluminescence (PL), which indicated that the introduction of rGO was responsible for well dispersion, smaller crystalline size, red shift of absorption band and suppressing quick photo-induced charges recombination of TiO_2-rGO/ASC photocatalysts. Optimization of operational parameters with 70 °C, 8% O_2 and 8% relative humidity were also obtained. Deactivation of TiO_2-rGO/ASC photocatalysts for NO removal was investigated by Fourier-transform infrared (FTIR) analysis. Regeneration experiments showed that thermal vapor regeneration would be optimal method owing to excellent regenerative capacity and inexpensive procedure.
[en] Graphical Abstract: Display Omitted - Abstract: Non-precious metal electrodes, Ni and Co hydroxides and oxides, have been recently found active towards electro-oxidation of methanol in alkaline. In this article, we present a first and complete study on composition dependence of Ni–Co hydroxides and oxides for methanol electro-oxidation. Ni–Co hydroxide electrodes were prepared by co-electrodeposition on stainless steel mesh (SSM). The atomic ratio of Ni/Ni + Co in Ni–Co hydroxides was controlled by adjusting the ratio of precursor concentration. Ni–Co oxide electrodes were further obtained by annealing the Ni–Co hydroxides. The morphology factors of Ni–Co hydroxides and oxides were revealed by measuring double layer capacitance using cyclic voltammetry (CV). Methanol oxidation reaction (MOR) performance of these Ni–Co hydroxides and oxide electrodes was investigated by CV, and electrochemical impedance spectroscopy (EIS) techniques at room temperature (RT, ∼25 °C). It is found that the MOR performance of Ni–Co hydroxides increased with the increase of Ni content, while the performance of Ni–Co oxide electrodes presented a volcano plot. The highest MOR performance, the smallest charge transfer resistance and Tafel slope were found at the atomic composition of 46% Ni. Such an enhancement probably was due to the synergistic effect of co-existing Ni and Co in the spinel structure. In contrast, the electrode with the mixture of Ni oxide and Co oxide was unable to reach such a high activity. The function of Ni in Ni–Co hydroxides and oxides was attributed to facilitating the methanol oxidation, and in low potential it presented high absorption of intermediate products
[en] Highlights: • A new graphene/K_3PW_1_2O_4_0 (GPW) composite was synthesized via photoreduction method. • Graphene in the GPW could reduce the recombination of electron-hole pairs. • Graphene in the GPW could increase adsorptive property. • GPW hybrid shows an enhancement photocatalytic activity. - Abstract: K_3PW_1_2O_4_0 is a promising polyoxometalate photocatalyst for the removal of organic pollutants from water. However, two main disadvantages of poor adsorptive performance and high recombination rate of photogenerated electron-hole pair hinder its practical applications. In this paper, a new graphene nanosheets/K_3PW_1_2O_4_0 nanocomposite has been synthesized via a green photoreduction strategy, being low-cost and scalable production. Characterizations show that K_3PW_1_2O_4_0 nanoparticles with 60 nm or so have been successfully deposited on the graphene nanosheets. As a kind of photocatalyst, the binary graphene nanosheets/K_3PW_1_2O_4_0 nanocomposite displays improved photocatalytic activity compared to pure K_3PW_1_2O_4_0. This improvement is ascribed to the introduction of graphene nanosheets in the nanocomposite, which could increase adsorptive property and reduce the recombination of electron-hole pairs.
[en] This article reports a composite electrode of Fe_2O_3 nanoparticles/SWCNTs for hydroquinone electrochemical sensing. The synthesis includes the wet-chemical synthesis of Fe_3O_4 nanoparticles and the assembly of Fe_3O_4 nanoparticles onto single walled carbon nanotubes. Fe_3O_4/NH_2-CNTs composite is formed via the electrostatic attraction between positively-charged ammonia-terminated CNTs and negatively-charged Fe_3O_4 nanoparticles. Subsequent heat treatment oxidizes Fe_3O_4 to Fe_2O_3. The composite can be applied onto FTO glass to form Fe_2O_3/CNTs/FTO electrode and the electrode shows good performance in electrochemical sensing of hydroquinone as compared to Fe_2O_3/FTO and CNTs/FTO electrodes. SEM and TEM results show the iron oxide NPs were uniformly dispersed onto the surface of SWCNTs. The iron oxide NPs which uniformly anchored on the SWCNTs could accelerate the electron transfer rate which was evidenced by electrochemical impedance spectroscopy. The enhancement of electrochemical response further confirms the synergy between Fe_2O_3 NPs and SWCNTs. Differential pulse voltammetry was successfully used to quantify hydroquinone within the concentration range of 1.0∼80.0 μM under optimal conditions. The detection limit of Fe_2O_3/CNTs/FTO electrode for hydroquinone was 0.50 μM (S/N = 3). The electrode was further applied to test for hydroquinone in tap water and the Fe_2O_3/CNTs/FTO electrode also presents good stability and high reproducibility, proofing the potential of Fe_2O_3/CNTs electrode as a promising electrochemical sensor. This work presents an electrode using FTO substrate for the first time. It shows that FTO can be a potential alternative to glassy carbon electrode with lower cost, but without compromising too much on the sensitivity.