A composite catalyst for the selective catalytic reduction (SCR) of NOx with NH3 is investigated, in which the rare earth (RE, including La, Ce, Pr, and Nd) is doped into manganese oxides supported on activated semi-coke (MnOx/ASC) via hydrothermal method at the molar ratio of Mn:RE = 1:5. It is evidenced that the addition of RE at a rather low molar ratio can enhance the catalytic activity of MnOx/ASC. The catalyst with a Mn:Ce molar ratio of 10:1 yields an over 90% NOx removal efficiency in the temperature range of 150–250 °C. An approximate 100% NO conversion and 95% N2 selectivity are achieved at about 200 °C. The catalysts are characterized by N2 physisorption, X-ray powder diffraction (XRD), scanning electron microscope (SEM), hydrogen temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the Ce additive is conducive to the NOx adsorption and then accelerates the SCR reaction due to the formation of more chemisorbed oxygen (Oβ), which is favored during the oxidation of NH3 and NO. Moreover, the in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) results confirm that the Ce additive on MnOx/ASC catalyst could provide more active Brønsted acid sites, which eventually contributes to the SCR reaction. The generation of ad-NH4+ and nitrite species is proved to play the crucial role in the promotional effect of RE addition.

•A ceramic tile base was prepared by using high alumina fly ash as main raw material.•Effects of adding high alumina fly ash and sintering temperature were investigated.•Macro and micro properties of the samples were systematically investigated.•The study provides a new method for efficiently utilizing the high alumina fly ash.To effectively utilize the industrial waste of high-alumina fly ash (HAFA), a ceramic tile base was successfully synthesized by the ceramic sintering process. In this research, the influence of HAFA addition and sintering temperature on properties were investigated. The results showed that the presence of ferruginous and calcareous minerals in HAFA decreased the inversion temperature of densification. Moreover, the optimum parameters were obtained at the sintering temperature of 1300 °C for 2 h with 70% HAFA, 15% clay and 15% quartz. In this research, the highest flexural strength reaches 67 MPa, and the corresponding bulk density and apparent porosity values are 2.43 g/cm3 and 0.13%, respectively.

For the purpose of building energy-saving, a novel one-piece wall ceramic board was prepared by using fly ash and ceramic waste as the main raw materials for its matrix part and foam part, respectively. The effects of raw material composition, sintering temperature on the macro and micro properties were systematically investigated. The optimum parameter for the matrix part was obtained at 1220 °C with 70 wt% fly ash and 4 wt% quartz, while that for the foam part was 1220 °C with 97 wt% ceramic waste and 3 wt% silicon carbide. For the matrix sample, the highest rupture modulus reaches 53.97 MPa, and the corresponding water absorption capacity and thermal conductivity are 1.08% and 0.54396 W/(m K), respectively. For the foam part, the best bulk density and thermal conductivity are 443 kg/m3 and 0.10528 W/(m K), respectively. Subsequently, the optimal matrix and foam samples were introduced into the co-fired process (1220 °C), and the results show that the new method for the preparation of one-piece wall ceramic board was fully acceptable. Furthermore, the simulated results indicate that the proposed one-piece wall ceramic board can efficiently reduce the thermal bridges and exerts excellent energy conservation effect.

•New permeable bricks were prepared by using gangue and tailings.•Effects of adding new aggregate and sintering temperature were investigated.•Effects of aggregates content and aggregates size were also investigated.•Fabrication was simplified without using natural clay and artificial aggregates.Gangue and tailings are both solid wastes produced by mining processing. In this study, permeable bricks were prepared by partial sintering of aggregates method, using gangue and tailings as aggregates and binder, respectively. The effects of aggregates content, aggregates size, sintering temperature and adding new aggregate on the permeability, apparent porosity, water absorption and mechanical properties of the prepared permeable bricks were systematically investigated. The optimum parameters to prepare the permeable bricks were obtained at 1180–1200 °C for 45 min with 20 wt% tailings, 60–70 wt% gangue and 10–20 wt% waste ceramic. The prepared permeable bricks, with the optimized parameters, have a high permeability (about 0.03 cm/s), exhibiting considerable compressive strength (exceeding 30 MPa). Combined with the macroscopic properties and microstructure analysis of the permeable bricks, the variation of the performance of permeable brick under different factors is studied. The preparation of permeable bricks using gangue and tailings may provide a promising way to reuse mine solid wastes, considering the advantages in both economic and environmental aspects.

Cerium oxides and neodymium-cerium composite oxides were loaded onto activated semi-coke (ASC) by a hydrothermal method for the selective catalytic reduction (SCR) of NO with NH3. The catalytic activity of CeO2/ASC was greatly enhanced by the addition of Nd. The mechanistic cause of the promoting effect of Nd was systematically investigated using various characterization techniques, including XRD, SEM, TEM and in situ DRIFTS. The results revealed that the reaction route for NH3-SCR followed both the E–R and L–H mechanisms over CeO2/ASC and CeO2-Nd/ASC catalysts. Nevertheless, the Nd doping process was beneficial for the formation of Ce3+ and gave rise to the transformation of Lewis acid sites into Brønsted acid sites, which influenced the mechanism of SCR reaction. The generation of oxygen vacancies was in favor of the oxidation of NO to NO2 and thus facilitated the proceeding of the following reduction reactions. Thus, the presence of the Ce3+ state and oxygen vacancies played a primary role in the improvement of the low-temperature SCR performance of the CeO2-Nd/ASC catalyst.

Hydrothermal treatment of cobalt nitrate in the presence of ZnO nanorod templates results in the generation of free-standing CoO–ZnO composite arrays on a copper substrate. The result shows that tuning the molar concentration of cobalt nitrate can controllably prepare CoO–ZnO nanotube and ZnCo2O4 hierarchical nanorod structures. The electrochemical properties of the resultant nanorod and nanotube arrays are investigated. Due to the short insertion and extraction length for lithium ions, the free space between the adjacent tubes or rods, and the high contact area, the as-prepared one-dimensional CoO–ZnO composites exhibit excellent cycling performance and high capacities as anode materials for Li-ion batteries.

Activated semi-coke, an economical carbonaceous material, is employed in the removal of SO2 from simulated flue gas of an industrial power plant. Activation by four commonly used agents, including CO2, KOH, ZnCl2, and H3PO4, is studied in detail, which demonstrates that the sample treated with KOH at high temperature presents the best performance on removal of SO2. Further investigation on the physical and chemical properties reveals that both optimized pore structure and increased amount of active sites of activated semi-coke could contribute to the high desulfurization capacity. The semi-coke activated with KOH is selected to discuss possible mechanisms of the adsorption and desorption processes. Performances with variation of desulfurization temperatures evidence that physically adsorbed SO2 can transform into chemically adsorbed SO2, which is significantly affected by temperature. Desulfurization behaviors under different flue gas compositions show that oxidation of SO2 to SO3 plays a key role in SO2 removal. By the analyzing desorption behavior of the samples, a reactive intermediate, C(O) complex, is proposed to be generated by dissociated chemisorption of O2 onto the surface of activated semi-coke, which serves as the dominating active site in oxidation of SO2. Besides, activated semi-coke exhibits several favorable properties in this study that could offer the prospect for further application in industrial desulfurization.

Nanosized CeO2 particles with a diameter of ∼200 nm were successfully loaded on activated carbon (AC) via a single-step hydrothermal process. The synthetic parameters, including hydrothermal temperature, precursor concentration, and reaction time, were regulated to control the size of the as-prepared CeO2 nanoparticles. The catalytic activity of CeO2 nanoparticles/AC was investigated by dynamic adsorption of SO2 from simulated flue gas, and the results exhibited remarkably enhanced SO2 adsorption capacity. The reaction mechanism of adsorbing and trapping SO2 by CeO2 nanoparticles/AC was discussed by laser Raman spectroscopy, X-ray powder diffraction, and thermodynamic calculations, which demonstrated that, in the presence of SO2 and O2, the generation of sulfate, accompanied by partial reduction of Ce4+ to Ce3+, was the key process during SO2 removal in our desulfurization experiments.

Ceria (CeO2) nanotube arrays with precisely defined size and density were directly synthesized on glass and cordierite substrates using a ZnO nanorods-assisted hydrothermal method. Eliminating the procedures of template removal and film coating, the one-step synthesis approach could greatly broaden the applications for materials with tubular structures. The proper concentration of cerium nitrate precursor solution acts a vital role to adjust the instantaneous precipitation of CeO2 and dissolution of ZnO templates. The as-prepared CeO2 tube arrays were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) techniques, which reveal a regular tubular structure with the average diameter of 500 nm and length of 3 μm. The automotive exhaust catalytic performance of CeO2 tube arrays prepared on the cordierite was evaluated. Compared with the ceria nanoparticles film, the target CeO2 tubes exhibit improved catalytic activities at a low start-up temperature for oxycarbide and hydrocarbon. Furthermore, the palladium-decorated CeO2 tubes exhibit a higher catalytic activity for the degradation of oxynitride than that of palladium/ceria particles/cordierite.

We present a two-step electrochemical deposition process to synthesize hierarchical zinc oxide (ZnO) nanorod-nanosheet structures on indium tin oxide (ITO) substrate, which involves electrodeposition of ZnO nanosheet arrays on the conductive glass substrate, followed by electrochemical growth of secondary ZnO nanorods on the backbone of the primary ZnO nanosheets. The formation mechanism of the hierarchical nanostructure is discussed. It is demonstrated that annealing treatment of the primary nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure. Photovoltaic properties of dye-sensitized solar cells (DSSCs) based on hierarchical ZnO nanostructures are investigated. The hierarchical ZnO nanorod-nanosheet DSSC exhibits improved device performance compared to the DSSC constructed using photoelectrode of bare ZnO nanosheet arrays. The improvement can be attributed to the enhanced dye loading, which is caused by the enlargement of internal surface area within the nanostructure photoelectrode. Furthermore, we perform a parametric study to determine the optimum geometric dimensions of the hierarchical ZnO nanorod-nanosheet photoelectrode through adjusting the preparation conditions of the first- and second-step deposition process. By utilizing a hierarchical nanostructure photoelectrode with film thickness of about 7 μm, the DSSC with an open-circuit voltage of 0.74 V and an overall power conversion efficiency of 3.12% is successfully obtained.Keywords: crystal growth; dye-sensitized solar cell; electrodeposition; hierarchical nanostructure; ZnO;

Branched hierarchical ZnO nanowire arrays are synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step electrochemical deposition process, which involves the electrodeposition of ZnO nanowire arrays on conductive glass substrate, followed by the electrochemical growth of ZnO nanorod branches on the backbones of the primary ZnO nanowires. The formation mechanism of the branched hierarchical nanostructure is discussed. It is demonstrated that coating the primary nanowire arrays with ZnO nanoparticles seed layer plays a key role in synthesising the branched hierarchical ZnO nanostructure. By adjusting the concentration of Zn(CH3COO)2 colloid in coating process and the reaction time of the second-step deposition, the density and the length of the secondary nanorod branches in the hierarchical nanostructures can be both varied. Moreover, the photoelectrochemical properties of the dye-sensitized solar cell (DSSC) based on branched hierarchical ZnO nanowire arrays are investigated. Due to the enlargement of the internal surface area within the branched nanostructure photoelectrode, the DSSC consisting of branched hierarchical ZnO nanowire arrays yields a power conversion efficiency of 0.88%, which is almost twice higher than that of the DSSC fabricated using bare ZnO nanowire arrays.Highlights► Branched hierarchical ZnO nanowires are synthesized via electrodeposition process. ► The diameter of the secondary ZnO nanorod branches is only about 30 nm. ► The density of the secondary ZnO nanorod branches can be well controlled. ► The obtained hierarchical nanostructure exhibits large internal surface area. ► Photoelectrochemical properties of the hierarchical nanostructure are investigated.

With the introduction of poly ethylene glycol (PEG) (10000), relatively well dispersed and oriented ZnO microrod arrays and ZnO microsphere arrays were successfully synthesized on unmodified indium tin oxide (ITO) substrate by a hydrothermal method. The growth behaviors of the two different kinds of ZnO arrays were experimentally investigated with variations of PEG addition and the precursor solution’s concentration. The PEG-assisted growth mechanism of ZnO microrod arrays and ZnO microsphere arrays has also been carefully discussed. Both the dissolved state of PEG and the interaction between PEG and ZnO crystalline grains were found to play important roles in the fabrication of the two different ZnO structure arrays. The research on PEG-assisted growth mechanism for these two kinds of ZnO structure arrays will provide more theoretical references for preparations of ZnO one-dimensional rod arrays and other kinds of assembled structures on the substrate.

Single crystalline SnO2 nanorod arrays with controlled size and high orientation consistency have been fabricated on a substrate in large scale by using a hydrothermal approach, and used as the photoanode in a Grätzel-type solar cell.

SnO2 nanograss array films (SNAFs) were synthesized on indium tin oxide glass substrates by hydrothermal method. The effects of preparing conditions such as precursor concentration, reaction temperature and growth time on the formation of the SNAFs have been investigated in detail by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and photoluminescence spectrum. It is shown that the precursor concentration plays an important role in determining the morphology of the prepared SnO2. The average diameter, length and growth rate of the SNAFs can be controlled to some extent by varying growth time. The reaction temperature has also influence on the growth rate of SNAFs. Moreover, the growth mechanism of the SNAFs was also discussed. Room-temperature photoluminescence spectra were further carried out to investigate their optical properties.

•We produced energy-saving building materials by using industrial solid waste.•The effect of steel slag and fly ash on the sample properties was investigated.•A modified model was applied to predict the effective thermal conductivity.•The modified model had better accuracy and shorter calculated time.A new kind of foamed cement (FC) made of Portland cement (PC), fly ash (FA), steel slag (SS), and foam agent has been developed with the purpose of preparing energy-saving building materials. The effect of SS and FA on the properties such as bulk density and compressive strength of base mix was systematically investigated. The results indicated that the base mix with 50% PC, 30% FA and 20% SS showed the optimum properties. By proper control in dosage of foam agent, a series of FC with a range of bulk densities (350–1340 kg/m3) were obtained for the further experimental measurement. The corresponding thermal conductivity (ke) of the samples was measured by a guarded hot plate apparatus. In addition, ke was also predicted by a modified model. Comparison with the previous model, the modified model had better accuracy and shorter calculated time. Finally the predictions were compared with the experimental data and other existing analytical models. The results indicated that the predicted results agree well with the measured values.

Hydrothermal treatment of cobalt nitrate in the presence of ZnO nanorod templates results in the generation of free-standing CoO–ZnO composite arrays on a copper substrate. The result shows that tuning the molar concentration of cobalt nitrate can controllably prepare CoO–ZnO nanotube and ZnCo2O4 hierarchical nanorod structures. The electrochemical properties of the resultant nanorod and nanotube arrays are investigated. Due to the short insertion and extraction length for lithium ions, the free space between the adjacent tubes or rods, and the high contact area, the as-prepared one-dimensional CoO–ZnO composites exhibit excellent cycling performance and high capacities as anode materials for Li-ion batteries.

Ceria (CeO2) nanotube arrays with precisely defined size and density were directly synthesized on glass and cordierite substrates using a ZnO nanorods-assisted hydrothermal method. Eliminating the procedures of template removal and film coating, the one-step synthesis approach could greatly broaden the applications for materials with tubular structures. The proper concentration of cerium nitrate precursor solution acts a vital role to adjust the instantaneous precipitation of CeO2 and dissolution of ZnO templates. The as-prepared CeO2 tube arrays were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) techniques, which reveal a regular tubular structure with the average diameter of 500 nm and length of 3 μm. The automotive exhaust catalytic performance of CeO2 tube arrays prepared on the cordierite was evaluated. Compared with the ceria nanoparticles film, the target CeO2 tubes exhibit improved catalytic activities at a low start-up temperature for oxycarbide and hydrocarbon. Furthermore, the palladium-decorated CeO2 tubes exhibit a higher catalytic activity for the degradation of oxynitride than that of palladium/ceria particles/cordierite.

Cerium oxides and neodymium-cerium composite oxides were loaded onto activated semi-coke (ASC) by a hydrothermal method for the selective catalytic reduction (SCR) of NO with NH3. The catalytic activity of CeO2/ASC was greatly enhanced by the addition of Nd. The mechanistic cause of the promoting effect of Nd was systematically investigated using various characterization techniques, including XRD, SEM, TEM and in situ DRIFTS. The results revealed that the reaction route for NH3-SCR followed both the E–R and L–H mechanisms over CeO2/ASC and CeO2-Nd/ASC catalysts. Nevertheless, the Nd doping process was beneficial for the formation of Ce3+ and gave rise to the transformation of Lewis acid sites into Brønsted acid sites, which influenced the mechanism of SCR reaction. The generation of oxygen vacancies was in favor of the oxidation of NO to NO2 and thus facilitated the proceeding of the following reduction reactions. Thus, the presence of the Ce3+ state and oxygen vacancies played a primary role in the improvement of the low-temperature SCR performance of the CeO2-Nd/ASC catalyst.