WO3 nanoparticles doped with Sb, Cd, and Ce were synthesized by a chemical method to enhance the sensing performance of WO3 for NO2 at room temperature. The doping with Sb element can significantly enhance the NO2-sensing properties of WO3. Upon exposure to 10 ppm of NO2, particularly the 2 wt % Sb-doped WO3 sample exhibits a 6.8-times higher response and an improved selectivity at room temperature compared with those of undoped WO3. The enhanced NO2-sensing mechanism of WO3 by doping is discussed in detail, which is mainly ascribed to the increase of oxygen vacancies in the doped WO3 samples as confirmed by Raman, photoluminescence, and X-ray photoelectron spectroscopy spectra. In addition, the narrower band gap may also be responsible for the enhancement of response as observed from the corresponding ultraviolet–visible spectra.

•NiFeOx/CoNx-C electrocatalyst was derived from CoPcTs-intercalated Ni2Fe- LDH.•It exhibits excellent ORR/OER bifunctional electrocatalytic activity and stability.•It shows high performance in a H2-O2 laminar flow unitized regenerative micro-cell.•The strong synergistic effect exists between Co-Nx and NiFeOx centers.We fabricated a NiFeOx/CoNy-C nanocomposite derived from CoPcTs-intercalated Ni2Fe-layered double hydroxides (Ni2Fe-CoPcTs-LDH), which served as high-efficiency, low-cost, and long-durability bifunctional oxygen electrocatalyst in half-cell, and a H2-O2 laminar flow unitized regenerative micro-cell (LFURMC) in alkaline media. Based on the synergistic effect between Co-Ny and NiFeOx centers, the non-noble hybrid catalyst NiFeOx/CoNy-C achieves a ΔE (η@jOER,10 - η@jORR,-3) = 0.84 V in alkaline solution, outperforming the commercial Pt/C, and very close to that of IrOx/C. In the fuel cell mode, the performance of NiFeOx/CoNy-C with the maximum power density of 56 mW cm−2 is similar to that of Pt/C (63 mW cm−2) and IrOx/C (58 mW cm−2); in the electrolysis mode, the calculated maximum electrical power consumed on NiFeOx/CoNy-C (237 mW cm−2) is more than 3 times that on Pt/C (73 mW cm−2), similar with that of IrOx/C. More importantly, the NiFeOx/CoNy-C shows a remarkable stability in alternating modes in a LFURMC system.Download high-res image (328KB)Download full-size image

A straightforward preparation of the antioxidant anion 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (DBHP), intercalated into layered double hydroxides (DBHP-LDH) via a co-precipitation method, and adjusting the (Mg, Zn, Al) metal ratio was reported. The influence of the Zn-containing LDH composition was studied by measuring the thermal stability and the DBHP anti-migration ability when dispersed into polypropylene (PP). The overall crystallinity of α-PP is found to remain similar with the dispersion of DBHP-LDH particles, but shaper diffraction peaks indicate the presence of larger crystallized domains, most probably arising from an anisotropic connection of smaller coherent PP domains with the help of PP chains diffusing inside the layered inorganic structure. The latter is acting as a coalescent agent yielding an intercalated PP nanocomposite structure with extended interfaces inducing a shift in the glass transition temperature to a higher temperature. The radical-scavenging activity of DBHP when interleaved between LDH layers is found to be conserved while an optimized cation composition for MgZnAl–DBHP is found for the thermo-oxidative stability in association with a lower DBHP migration among the PP nanocomposite series, making the resulting PP nanocomposite a highly promising candidate for possible applications.

•Porous MgO prepared by hexamethylene tetramine-assisted hydrothermal method.•HMT plays a key role during the formation of pore structure of MgO materials.•Magnesium hydrogen phosphate and magnesium phosphate were formed around MgO.Porous magnesium oxide as the adsorbent of phosphate was prepared by hexamethylene tetramine (HMT) assisted hydrothermal method. Various techniques were used to carefully characterize crystallinity structure, morphology, pore structure, and adsorption performance of the prepared MgO samples. The results show that the HMT plays a key role during the formation of pore structure of MgO materials. The BET surface area and pore size were varied as a function of the feeding ratio of HMT and Mg2+ in the synthesis system. When the ratio is equal to 1.2, the obtained MgO sample has the appropriate BET surface area of 181.02 m2 g−1 and the averaged pore diameter of ca. 10.76 nm, which shows the highest adsorption capacity of 236 mg g−1 among the prepared samples and the outstanding adsorption performance compared with those reported in the literature. The adsorption of these porous MgO materials matches well the pseudo second order kinetic model and the Freundlich isotherms. Besides, the phosphate anions was adsorbed on MgO to produce magnesium hydrogen phosphate and magnesium phosphate.

One of the major issues for poly(propylene) PP concerns its protection towards oxidative phenomena resulting in polymer failure. Using known anti-oxidant (AO), Irganox 1425, an original approach is taking advantage of the counterion, cations Ca2+, in building hydrocalumite inorganic sheets, and concomitantly providing the AO anions to be immobilized within an inorganic host structure. Through the classical co-precipitation method, the hybrid assembly composed of AO molecules interleaved between hydrocalumite layered structure is successfully elaborated in one-step process free of contamination. Hydrocalumite (Ca2Al) belongs to the family of layered double hydroxides (LDH). The structure of the AO-LDH hybrid material is determined by means of XRD, FT-IR, while the radical-scavenging activity of AO-LDH is investigated using DPPH• (1,1-Diphenyl-2-picryl-hydrazyl) radical concentration variation. A series of AO-LDH/PP composites is then obtained by dispersing AO-LDH into PP at different loading ratios, and addressing the thermal stability, light stability and anti-migration of the resulting composites. The use of hydrocalumite vessel in confining AO molecules helps to increase the thermal stability and resistance against the photo oxidation while providing a barrier effect against organic species migration. An optimized of 4 wt% AO-LDH into PP results in the best radical-scavenging activity, 1 wt% is preferred to stabilize PP under light, the former formulation is the best compromise of all the series.

•SDS intercalated Ni2Fe-LDHs with different interlayer distances were prepared.•OER activity of Ni2Fe-SDS-LDH/CFP were related with the interlayer distance.•Electrocatalytic performance is higher than commercial IrO2 in alkaline medium.Herein, a series of three-dimensional Ni2Fe-SDS-LDH/CFP non-precious metal electrocatalysts in a simple hydrothermal route using sodium dodecyl sulfonate (SDS) as an interlayer spacer agent, and carbon fiber paper (CFP) as a conductive substrate was tailored. The electrocatalytic performance towards oxygen evolution reaction (OER) in alkaline medium was investigated. The results demonstrate that the OER activity improvement is mainly related to the increased interlayer distance from 0.76 nm to 2.49 nm depending on the intercalated amount of SDS in Ni2Fe-LDH, and resulting in the enhanced superior surface characteristics (e.g., larger specific surface area, bigger pore size and pore volume). Among all the samples, the Ni2Fe-SDS-LDH/CFP (molar ratio SDS/Fe = 1.5) showed the best OER performance (η@10 mA cm−2 = 289 mV, Tafel slope = 39 mV dec−1) comparable with the commercial IrO2 catalyst, which corresponded to the largest interlayer space of 2.49 nm.A series of three-dimensional Ni2Fe-SDS-LDH/CFP non-precious metal electrocatalysts in a simple hydrothermal route using sodium dodecyl sulfonate (SDS) as an interlayer spacer agent, and carbon fiber paper (CFP) as a conductive substrate was tailored. The electrocatalytic performance towards oxygen evolution reaction (OER) in alkaline medium was investigated. The results demonstrate that the OER activity improvement is mainly related to the increased interlayer distance from 0.76 nm to 2.49 nm, depending on the intercalation amount of SDS in the Ni2Fe-LDH. Among all samples, the Ni2Fe-SDS-LDH/CFP (molar ratio SDS/Fe = 1.5) showed the best OER performance (η@10 mA cm−2 = 289 mV, Tafel slope = 39 mV dec−1) comparable with the commercial IrO2 catalyst, which corresponded to the largest interlayer space of 2.49 nm.Download high-res image (257KB)Download full-size image

A metal organic framework (MOF), synthesized from cobalt salt, melamine (mela), and 1,4-dicarboxybezene (BDC), was used as precursor to prepare Co/CoNx/N-CNT/C electrocatalyst via heat treatment at different temperature (700–900 °C) under nitrogen atmosphere. Crystallites size and microstrain in the 800 °C heat-treated sample (MOFs-800) were the lowest, whereas the stacking fault value was the highest among the rest of the homemade samples, as attested to by the Williamson–Hall analysis, hence assessing that the structural or/and surface modification of Co nanoparticles (NPs), found in MOFs-800, was different from that in other samples. CNTs in MOFs-800, interacting with Co NPs, were formed on the surface of the support, keeping the hexagonal shape of the initial MOF. Among the three homemade samples, the MOF-800 sample, with the best electrocatalytic performance toward oxygen reduction reaction (ORR) in 0.1 M KOH solution, showed the highest density of CNTs skin on the support, the lowest ID/IG ratio, and the largest N atomic content in form of pyridinic-N, CoNx, pyrrolic-N, graphitic-N, and oxidized-N species. Based on the binding energy shift toward lower energies, a strong interaction between the active site and the support was identified for MOFs-800 sample. The number of electron transfer was 3.8 on MOFs-800, close to the value of 4.0 determined on the Pt/C benchmark, thus implying a fast and efficient multielectron reduction of molecular oxygen on CoNx active sites. In addition, the chronoamperometric response within 24 000 s showed a more stable current density at 0.69 V/RHE on MOFs-800 as compared with that of Pt/C.Keywords: cobalt nanoparticles; metal−organic framework; nitrogen-doped carbon nanotube; nonprecious metal electrocatalysts; oxygen reduction reaction;

It remains a big challenge to develop high-efficiency and low-cost adsorption materials to remove toxic heavy metal ions in water. Here, we developed a template-free synthesis method to fabricate high surface area and large pore size magnesium silicate hierarchical nanostructures in a mixed solvent of ethanol and water and carefully investigated the corresponding adsorption behavior for Pb2+, Zn2+, and Cu2+ in aqueous solution. The results reveal that the ethanol volume fraction in the solvent plays an important role to optimize the pore structure, which directly determines the adsorption capacity and the adsorption rate for heavy metal ions. When the ethanol volume fraction is beyond 50%, the obtained magnesium silicate presents a flowerlike structure with a hierarchical pore distribution: 0.5–2, 2–30, and 30–200 nm. When the ethanol volume faction is 90%, for example, the sample exhibits a maximum adsorption capacity of 436.68, 78.86, and 52.30 mg/g for Pb2+, Zn2+, and Cu2+ ions, which has a BET surface area of 650.50 m2/g and an average pore diameter of 6.89 nm, respectively. Also, the sample presents excellent repeated adsorption performance after three elutions. The obtained materials show widely promising and practical applications in water treatment in a wide pH range from 2.8 to 5.8.Keywords: Adsorption; Heavy metal ions; Magnesium silicate; Recyclability; Template-free;

•High-surface-area pseudoboehmite was synthesized in a template-free route.•Spherical γ-Al2O3 was prepared in a simple and promoter free way.•Spherical γ-Al2O3 has higher hydrothermal stability than the commercial one.It is of great industry interest to develop spherical γ-Al2O3 support with high surface area and high hydrothermal stability. In this work, we developed a simple and promoter free way to prepare spherical γ-Al2O3 support with high hydrothermal stability from homemade pseudoboehmite with high surface area. The structure, morphology, pore structure and hydrothermal stability of the prepared materials were characterized and analyzed by various techniques such as XRD, SEM, TEM and low temperature N2 adsorption. The pseudoboehmite has a large BET surface area (SBET) of 444 m2 g−1 and the spherical γ-Al2O3 has high hydrothermal stability under the investigated conditions. After hydrothermal treatment at 600 °C for 192 h, the SBET of the spherical γ-Al2O3 remains 183 m2 g−1, which is much higher than that of 148 m2 g−1 for the commercial γ-Al2O3 from Sasol.We report a simple and promoter free synthesis of spherical γ-Al2O3 catalyst support with high hydrothermal stability from homemade pseudoboehmite with high surface area. The spherical γ-Al2O3 exhibits higher hydrothermal stability compared with the commercial γ-Al2O3 sample from Sasol.

•Spherical ZSM-5/α-Al2O3 prepared by an in situ growth method.•Ca. 2.4 wt% ZSM-5 is produced on the surface of α-Al2O3.•ZSM-5 enhances surface acidity and BET surface area of α-Al2O3.In this work, we have developed an in situ growth method to synthesize spherical ZSM-5/α-Al2O3 composite on spherical α-Al2O3 and investigated the morphology, structure, and properties of this composite using scanning electron microscope (SEM), powder X-ray diffraction analysis (XRD), NH3-temperature program desorption (NH3-TPD) and low temperature N2 adsorption–desorption isotherm (BET). The results show that ca. 2.4 wt% ZSM-5 has been formed in the composite with a Si/Al ratio of 46.5 and an average particle size of 8.04 μm. Furthermore, the formed ZSM-5 markedly enhances the surface acidity and the BET surface area of spherical α-Al2O3 support.

Non-precious metal chalcogenides are considered as a potential alternative to Pt-based cathode catalysts in polymer electrolyte membrane fuel cells because of their promising electrocatalytic performance and low cost. However, size-controlled synthesis of this class of materials still remains a big challenge. In this paper, we directly prepared CoS2 nanocatalysts by a hydrothermal route without any post treatment, developed a facile way to tune the particle size by adjusting the initial Co2+ concentration in the reaction system in the presence of a surfactant, and investigated the corresponding electrocatalytic performance for the oxygen reduction reaction (ORR) in alkaline medium in detail. The results show that the ORR activity mainly depends on the CoS2 mass loading on the electrode disk surface and the average particle size of the CoS2 nanocatalysts. The CoS2 catalyst with an average particle size of 30.7 nm exhibits excellent electrocatalytic performance with an OCP (open circuit potential) of 0.94 V vs. RHE, a half-wave potential (E1/2) of ca. 0.71 V vs. RHE, and complete methanol tolerance for the ORR in 0.1 M KOH. This OCP value is the largest among non-precious metal chalcogenides to date, much close to that of 0.99 V vs. RHE for commercial Pt/C catalyst (E-TEK). In addition, the CoS2 nanocatalyst has comparable durability to the Pt/C catalyst in 0.1 M KOH. The CoS2 nanocatalyst is a promising candidate for alkaline membraneless fuel cell systems.

Mordant yellow 3 (MY3) anions have been intercalated into Zn-Al layered double hydroxides (LDH) to produce a novel intercalation compound pigment by a direct coprecipitation method. The prepared composite was characterized by various techniques such as powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry and differential thermal analysis (TGA-DTA), and UV–vis spectroscopy. The obtained results show that MY3 anions were intercalated into the interlayer spacing of LDH as observed from PXRD and FT-IR. Furthermore, the intercalation of MY3 anions into the LDH markedly enhances the thermo- and photostability of MY3, which may enlarge the practical application fields of MY3 dye.

Non-precious metal chalcogenides are considered as a potential alternative to Pt-based cathode catalysts in polymer electrolyte membrane fuel cells because of their promising electrocatalytic performance and low cost. However, size-controlled synthesis of this class of materials still remains a big challenge. In this paper, we directly prepared CoS2 nanocatalysts by a hydrothermal route without any post treatment, developed a facile way to tune the particle size by adjusting the initial Co2+ concentration in the reaction system in the presence of a surfactant, and investigated the corresponding electrocatalytic performance for the oxygen reduction reaction (ORR) in alkaline medium in detail. The results show that the ORR activity mainly depends on the CoS2 mass loading on the electrode disk surface and the average particle size of the CoS2 nanocatalysts. The CoS2 catalyst with an average particle size of 30.7 nm exhibits excellent electrocatalytic performance with an OCP (open circuit potential) of 0.94 V vs. RHE, a half-wave potential (E1/2) of ca. 0.71 V vs. RHE, and complete methanol tolerance for the ORR in 0.1 M KOH. This OCP value is the largest among non-precious metal chalcogenides to date, much close to that of 0.99 V vs. RHE for commercial Pt/C catalyst (E-TEK). In addition, the CoS2 nanocatalyst has comparable durability to the Pt/C catalyst in 0.1 M KOH. The CoS2 nanocatalyst is a promising candidate for alkaline membraneless fuel cell systems.