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Noble metal-free MoS2/g-C3N4 photocatalysts have been synthetized by one step thermal treatment of thiourea and sodium molybdate, which has intimate contact interfaces between g-C3N4 and MoS2. The hydrogen generation rate of MoS2/g-C3N4 photocatalyst is 280 µmol·g−1·h−1, 40 times as that of pristine g-C3N4. The enhanced activity is attributed to the in-situ generated intimate interfaces, which leads to enhanced absorption of visible light and higher efficiency of charges separation.

Utilizing photocatalysts to split water into H2 and H2O2 simultaneously is an ideal but challenging process to obtain clean H2 energy and high valuable H2O2. Most of the photocatalysts currently studied for the overall water splitting are converting water into H2 and O2, resulting in further need of gas separation. Here, we reported a photocatalyst which can utilize the nano-Au based localized surface plasmonic resonance (LSPR) effect to produce H2 and H2O2 simultaneously. Nitrogen doped graphene quantum dots (N-GQDs) pieced together into large graphene through a catalytic process by chloroauric acid, in which dodecahedron nano-Au particles can also be obtained concurrently. Then Au wrapped up by graphene can be in situ formed with good interfaces. Photocatalytic activity tests revealed that the as prepared graphene@Au catalysts show efficient photocatalytic overall water splitting activity with a H2 evolution rate of 65.6 μmol g−1 h−1 and H2O2 generation rate of 49.7 μmol g−1 h−1. This work provides a feasible route for the facile fabrication of graphene through the bottom-up polycondensation of N-GQDs by amide bonds and new insights into the synthesis of photocatalysts for overall water splitting into H2 and H2O2.

A high-quality hybrid Cs0.15FA0.85PbI3 thin film is deposited through doping of carbon nanodots (CNDs) into perovskite precursor solution. The corresponding inverted planar perovskite solar cells (PSCs) of ITO/PTAA/Cs0.15FA0.85PbI3/PC61BM/BCP/Ag exhibit an improvement in efficiency from 17.36% to 20.06%, which could be attributed to the passivation of the defects at the crystallized perovskite thin film and enhanced perovskite phase uniformity. The results of electron trap density indicate that the addition of CNDs significantly reduces the defects density at the perovskite thin film and the recombination of charge carriers in transport process is minimized. These results demonstrate that low-cost CNDs are effective additives for passivating defects, further reducing charge carrier recombination and improving device efficiency.

Pt/Al2O3 catalysts with mean Pt particle size ranged from 2.7 to 7.1 nm were synthesized by chemical reduction method, and the sulfated counterparts were prepared by impregnation of sulfuric acid. The turnover frequency of platinum for soot oxidation under loose contact conditions in a feed flow containing NO and O2 are positively correlated with the size of platinum. The sulfated Pt/Al2O3 exhibits higher catalytic activity for soot oxidation in the presence of NO despite their reduced ability for NO2 production. Such a contradiction is more significant for those catalysts with smaller platinum particles. Herein, the catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), inductive coupled plasma (ICP) emission spectrometry, CO chemisorption, thermogravimetric analysis (TGA), NH3 temperature-programmed desorption (NH3-TPD), NO temperature-programmed oxidation (TPO) and NOx temperature-programmed desorption (TPD). Possible effect of Pt particle size for the catalytic oxidation of soot in the presence of NO was presented based primarily on the promoted NO2 transfer efficiency onto the soot pushed by the acidic catalysts.

A series of La1–xCexMnO3+δ (x = 0, 0.05, 0.1, 0.2, and 0.3) perovskites and Mn–Ce mixed oxides were prepared. Their physico-chemical properties were systematically characterized and the NO oxidation activities of the catalysts were investigated. The La0.9Ce0.1MnO3+δ has the best activity among all of the catalysts, with a maximum NO conversion of 85% at 300 °C. The characterization results indicate that the doping of Ce improves the properties of the perovskites in terms of the specific surface area, the average valence state of Mn ions, the number of reactive oxygen species and the NOx desorption behaviors. The Mn–Ce mixed oxide calcined at 500 °C shows a similar NO oxidation activity with La0.9Ce0.1MnO3+δ. However, the activity of the mixed oxide obtained at 750 °C decreases a lot, which results from the loss of active sites and active oxygen species.

Cu-SSZ-13 catalyst, as the most popular selective catalytic reduction on filter (SCRF) catalyst in diesel exhaust purification, may suffer from severe alkali deposition derived from engine oil, urea solution and biodiesel fuel. These accumulated deposits inevitably affect both of the NOx reduction and soot oxidation reactions. Unlike deactivation effect of alkali impurities on Cu-SSZ-13 catalyst for NH3-SCR process, which has been extensively studied and well documented, the impact of alkali deposition on soot oxidation over SCRF catalyst is still poorly understood. Herein, we reported the influence of potassium salts deposition on soot oxidation of Cu-SSZ-13 catalyst. Compared with the fresh Cu-SSZ-13, these K-impregnated catalysts show promoted activities toward soot oxidation with the promotion effect of K2SO4 > K2CO3 > K3PO4. The generated copper compounds instead of potassium salts are found to be responsible for the enhanced catalytic activity. The NO oxidation over the K2CO3-impregnated catalyst is accelerated by CuOx clusters, resulting in a low ignition temperature toward soot oxidation in the presence of NOx. Contrarily, K2SO4- and K3PO4-impregnated catalysts show higher ignition temperature values because the generated copper sulfates and phosphates present weakened NO oxidation activities especially in the low-temperature region. This work provides new insight into understanding the affecting mechanism of alkali impurities on SCRF catalysts. The generated Cu species induced by the deposition of different potassium salts, rather than alkali species themselves, are responsible for the promoted soot oxidation activity of the K-impregnated Cu-SSZ-13 as a SCRF catalyst.

Pt@g-C3N4/CeO2 photocatalyst was prepared by calcination of g-C3N4/CeO2 mixture followed by impregnating Pt. Under the irradiation of visible light with the presence of water vapor at room temperature, Pt@g-C3N4/CeO2 showed significant performance for remediation of NOx. The deNOx mechanism was studied by modified in-situ FTIR. The results proved that NO was prone to adsorb on the surface of Pt@CeO2 and oxidized to nitrite for storage. Then, the photoinduced hydrogen on Pt@g-C3N4 component could diffuse into the vicinity of nitrite through the spillover effect of Pt and reacted with nitride to produce N2 and H2O.

The interface architecture plays important role in the charge transfer and separation of S-scheme photocatalysis. Herein, we propose a strategy to synthesize (reduced graphene oxide, γ-Fe2O3)/C3N4 S-scheme heterojunctions by thermal treatment of MIL-101(Fe) and melamine. (rGO, γ-Fe2O3)/C3N4 presents a high oxygen evolution rate (OER) of 3.85 mmol·g−1·h−1 under visible irradiation, and overall water splitting activity with the hydrogen evolution (HER) and OER rates of 23.3 and 12 μmol·g−1·h−1, respectively. The band alignments by different Fermi levels of C3N4 and (rGO, γ-Fe2O3) result in internal electric field, which significantly enhances the separation efficiency of photogenerated electrons and holes.

A facile way to synthesize multilayer nitrogen-doped graphene (NG) from amorphous activated carbon (AC) without metal catalyst was successfully developed via ammonia-assisted hydrothermal method at 200 °C. The method's crucial advantage relied on harnessing unique ammonia hydrothermal mechanisms to change the amorphous carbon into multilayer graphene and provide an energy-save and metal-free approach. The NG products were consisted of 2–10 graphitic layers, which could form highly conductive network for electrodes. The hydrothermal process could trigger the reduction of oxygenates on the base unit (graphite nanocrystallites) of amorphous carbon by ammonia, leading to growth of basic units to multi-layer graphene. Compared with the traditional preparation via high temperature and pressure processing or catalytic graphitization by transition metals, the as-prepared multilayer graphene via metal-free and “green” method in a relative mild condition represented a high surface area and pore volume. The NG was used as electrode material of supercapacitors and showed high capacitance retention.

Solid-state ion-exchange (SSIE) is an effictive method to prepare Cu-SSZ-13, but usually requires high temperatures or assistance of NH3 for catalyst activation. Herein, an environmentally friendly...

NaOH-promoted Pt/TiO2 catalysts are successfully prepared by a facile impregnation method assisted by NaOH and tested for the toluene oxidation reaction under visible light irradiation. Keeping molar ratio of Pt:Na = 1:8, the 0.1Pt-Na/TiO2 catalyst (0.1 mol% Pt) shows excellent catalytic performance with more than 60% of toluene conversion at 45 °C and achieving total toluene removal at 280 °C, which is significantly better than 0.1Pt/TiO2 catalyst. The structures and properties of catalysts are characterized by XRD, SEM, N2 adsorption, XPS and UV–vis spectra. The positively charged Pt species stabilized by NaOH are the most active sites for photo-thermal catalyzing toluene oxidation. The influence of Pt loading and the effect of supports (active TiO2 and inert Al2O3) are also discussed.

Copper catalysts were widely developed for CO2 conversion, but suffered severe sintering at temperatures higher than 300 °C. Platinum was the most active and stable metal for RWGS reactions. However, the high price and scarcity of platinum restrained its application. Downsizing the metal particles can significantly improve the atom efficiency of the precious metal but the size effect of Pt on RWGS reactions was still unclear. In the present work, the single atomic Pt on SrTiO3 was prepared using an impregnation leaching method, and the catalyst showed significant activity for an RWGS reaction, achieving a CO2 conversion rate of 45%, a CO selectivity of 100% and a TOF of 0.643 s−1 at 500 °C. The structures of the catalysts were characterized using XRD, STEM and EXAFS. Especially, the size effect of Pt in RWGS was researched using in situ FTIR and DFT calculations. The results reveal that single Pt atoms are the most active species in RWGS via a “–COOH route” while larger Pt cluster and nanoparticles facilitate the further hydrogenation of CO. The reaction between formate and H* is the rate determination step of an RWGS reaction on a catalyst, in which the reaction barrier can be lowered from 1.54 eV on Pt clusters to 1.29 eV on a single atomic Pt.

Heterogeneous thermocatalysis is widely used for the removal of VOCs. However, it is energy-consuming because it must operate at high temperatures. Combining thermocatalysis with photocatalysis makes it possible for the efficient abatement of VOCs at low temperatures. In this work, Pd–Ag@CeO2 photothermal catalyst was synthesized via synthesizing ceria-coated Ag nanoparticles followed by loading Pd nanoparticles by the liquid-phase reduction method. The catalyst has a core–shell structure which induces strong electron interactions between Pd/Ag and CeO2 and significantly improves the light harvest, charge separation and dissociative adsorption of Pd–Ag@CeO2 in the visible region. The Pd–Ag@CeO2 catalyst has a good catalytic performance in toluene oxidation, showing the T50 of Pd–Ag@CeO2 at only 88 °C under visible light irradiation. Finally, the possible catalytic mechanism has also been proposed for the oxidation of toluene under visible light irradiation.

A series of Cu–SAPO-34 catalysts with different copper contents were prepared using a modified ion-exchange method, i.e., impregnation–activation. Controlled amounts of well-dispersed active copper species and integrated physical properties were obtained by this method. The Cu–SAPO-34 catalysts retained the CHA structure, high specific surface area, and pore volume of the H–SAPO-34. Based on a combined analysis of UV–vis spectra and H2-TPR, these common laboratory techniques enabled the identification of the different copper species present in the catalysts. Only isolated copper ions balanced by two framework charges were present in the catalysts at copper contents ≤ 0.8 wt%. With increasing the Cu content, isolated Cu2+ ions charge-balanced by one negative charge became dominant. Further higher Cu contents could result in formation of copper oxides after consumption of all ion-exchange sites.

MoS2/Ag3PO4 heterojunction photocatalysts have attracted great attention in dye degradation and water oxidation, in which Z-scheme plays a critical role in the catalytic performance as a result of energy band structure alignment between MoS2 and Ag3PO4. Creating metal sites at composite interfaces as recombination centers of photo-generated electrons from conduction band (CB) of Ag3PO4 and holes from valence band (VB) of MoS2 is an effective strategy to enhance the charge separation efficiency and photocatalytic performance. Strong coupled MoS2/Ag dots/Ag3PO4 ternary heterojunction photocatalysts were fabricated by one-pot precipitation method, in which highly dispersed Ag dots are located at the MoS2/Ag3PO4 interfaces and MoS2 is bonded with PO43- in the form of Mo-O-P. The fabricated MoS2/Ag dots/Ag3PO4 photocatalyst presents a 2.8-fold enhancement of photocatalytic activity of water oxidation compared to that of pristine Ag3PO4, which is achieved for the first time. The great enhancement of photocatalytic performance can be ascribed to the improved Z scheme mechanism with strongly coupled MoS2/Ag dots/Ag3PO4 ternary interfaces, in which highly dispersed Ag dots serve as efficient recombination centers resulting in the improved separation of photo-generated holes and electrons of Ag3PO4 as well as photocatalytic activity of oxygen evolution.

Noble metal free MoS2/g-C3N4 catalyst has attracted intense attentions for visible light photocatalytic hydrogen evolution as a result of its earth abundance, low cost and unique heterojunctions stacked with two dimensional sheets. However, the low charge separation efficiency resulted from the poor conductivity of g-C3N4 and MoS2, and lack of abundant active sites from coordinative unsaturated atoms in MoS2, restricts the photocatalytic hydrogen evolution activity and stability enhancement of MoS2/C3N4 composite catalysts. Herein, CoMoS2/rGO/g-C3N4 catalysts with ternary heterojunctions are prepared by facile solvothermal method, which exhibit high visible light photocatalytic activity and stability for hydrogen evolution. The optimal hydrogen evolution rate of CoMoS2/rGO/g-C3N4 catalysts is 684 μmol g−1 h−1 when the content of CoMoS2 is 2% and the content of rGO is 0.5%. The stability of CoMoS2/rGO/C3N4 catalysts just decrease about 3% after 4 cycling runs for 16 h. The good catalytic performances of catalysts are attributed to the synergistic effect among the g-C3N4 nanosheets, rGO nanosheets and CoMoS2 nanosheets. The high conductivity of rGO nanosheets enhances the electron-hole separation and charge transfer, and Co doping increases the active sites for hydrogen evolution due to the increase of unsaturated atoms in CoMoS2 nanosheets.

Noble metal-free NiS/P-S codoped g-C3N4 (PSCN) nanocomposites were fabricated by combination of thermal copolymerization using ammonium O, O- diethyl dithiophosphate as P-S precursor and ion-exchange precipitation. The optimal H2-generation rate of NiS/PSCN is 30.5 μmol h− 1, which is 1.9 times higher than that of NiS/pristine g-C3N4. The codoping of P and S into g-C3N4 not only enhances the light harvesting, but also promotes the charge separation. Noble metal-free NiS loaded onto PSCN serves as electron trapping centers and active sites for hydrogen evolution which further enhances the photocatalytic H2 evolution activity of PSCN.

Mn/Ce/Ti and Mn/Ce/Nb/Ti catalysts were synthesized using a precipitation method and their catalytic activities for NO selective reduction with NH 3 at low temperatures were evaluated. Nb doping not only improved the activity of the catalyst over a wide temperature range but also restricted the generation of NO 2 and N 2 O. The Mn/Ce/Nb/Ti catalyst displayed 100% NO conversion from 150 to 250 °C and >90% N 2 selectivity below 250 °C. The specific surface area of the catalyst was increased and its surface acidity was strengthened after Nb doping. Moreover, Nb doping increased the NO oxidation ability and lowered the NH 3 oxidation activity of the catalyst. All the above factors contributed to enhancing the overall NH 3 -SCR performance of the Mn/Ce/Nb/Ti catalyst compared with that of the Mn/Ce/Ti one. The long-term stability and resistance to H 2 O and SO 2 of the Mn/Ce/Nb/Ti catalyst were also evaluated.

A photocatalytic CeO 2 @TiO 2 core–shell nanocomposite with enhanced photocatalytic performance was synthesized via a simple hydrothermal route assisted with the Stober method. The TiO 2 coating layer consisting of fine TiO 2 crystallites contributed most of the surface area of the CeO 2 @TiO 2 nanocomposite. The CeO 2 @TiO 2 nanocomposite exhibited a significantly narrower optical band gap than that of the pure TiO 2 . Photocatalytic studies revealed that the CeO 2 @TiO 2 core–shell nanocomposite displayed higher photocatalytic activity than both CeO 2 nanocubes and TiO 2 in degradation of the organic pollutant Rhodamine B. Such varieties in optical band gap and photocatalytic activity were assigned to the heterojunction interfaces formed in CeO 2 @TiO 2 , which could both promote photoinduced charge separation and suppress the recombination of photogenerated electrons and holes. During the process, the reversible oxidation-reduction in Ce(IV)/Ce(III) redox couples also promoted the efficient electron transfer.

Cu-modified SAPO-34 molecular sieves with different Cu loading amounts were prepared by ion-exchange and impregnation methods. Both series of catalysts were hydrothermally treated at 750 °C in 10 vol% H 2 O/air for 24 h. The catalysts were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction (H 2 -TPR), NH 3 temperature-programmed desorption (NH 3 -TPD) and diffused reflectance infrared flourier transform spectroscopy (DRIFTS). All the fresh catalysts show high activity toward the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) at low temperatures regardless of preparation method. Generally, the hydrothermal aging shifts the operation window of the catalysts towards high temperatures. The improvement in high-temperatures activity is attributed to the migration of surface CuO clusters into the ion-exchanged sites as isolated Cu 2+ during ageing, which suppresses the competitive oxidation of NH 3 . The loss of low-temperatures activity is also related to the decrease in the amount of active surface CuO clusters, inhibiting the oxidation of NO to NO 2 and fast SCR reaction. Interestingly, the amount of Lewis acid sites increase linearly with the increasing isolated Cu 2+ , while the Bronsted acidity is weakened.

NH4NO3 species are proved to be important and stable intermediates in NH3-SCR reactions on ceria catalysts. The decomposition behaviors of NH4NO3 were studied by Diffuse Reflectance Infrared Fourier Transformed Spectra (DRIFTS), Thermo Gravimetry/Differential Scanning Calorimetry (TG/DSC) and Mass Spectrometry (MS). MnOx–CeO2 catalysts synthesized by a co-precipitation method show 90% NOx conversion at 120–180 °C and ZrPO4–CeO2 catalysts were prepared by loading zirconium phosphate on CeO2, which present over 90% NOx conversion at 250–450 °C. Decomposition of NH4NO3 on the ceria catalyst is determined by both the redox properties and acidity of the catalyst, which further influence the catalyst's temperature window. For the decomposition of NH4NO3 on the MnOx–CeO2 catalyst with higher redox properties but much lower acidity, nitrate species can react with NO to generate nitrite, then react with gaseous NH3 to form NH4NO2 and finally decompose into N2 + H2O at 120 °C, in which process NH4NO3 can be considered as the important intermediate of the NH3-SCR reaction at 120–180 °C. At temperatures below 90 °C, NH4NO3 on MnOx–CeO2 can be a poison blocking the active sites. While on the ZrPO4–CeO2 catalyst with lower redox properties but higher acidity, two distinct sites for NH3 and NOx adsorption lead to the strong interaction between ads-NH4+ and nitrates, resulting in the decomposition temperature of NH4NO3 elevating to 250 °C, which is also the threshold of the catalyst's temperature window. At temperatures over 250 °C, NH4NO3 is an intermediate on the ZrPO4–CeO2 catalyst in participating the NH3-SCR reaction.

Cu/SAPO-34 catalysts were prepared by wet impregnation and ion-exchange methods, and both the catalysts were hydrothermally treated at 750 °C in 10 vol% H2O/air for 24 h. Subsequently, the as-received and hydrothermally treated catalysts were exposed to a sulfur poisoning treatment at 350 °C in 100 ppm SO2/10 vol% H2O/air for 24 h and examined for NOx conversion. Sulfur poisoning considerably decreased the NOx conversion efficiency of the catalysts at low temperatures. In contrast, it improved the high-temperature selective catalytic reduction (SCR) activities of the as-received catalysts. The ion-exchange-prepared catalysts displayed higher sulfur tolerance than the impregnation-prepared catalysts at 150–350 °C. The electron paramagnetic resonance, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and H2-temperature-programmed reduction results showed that sulfur poisoning significantly influenced the migration of the copper species and thereby the amount of active isolated Cu2+. More dispersed CuSO4 was produced on the ion-exchange-prepared catalysts than on the impregnation-prepared catalysts after sulfur poisoning. The dispersed CuSO4 showed considerably higher SCR activity than the crystalline CuSO4. Both the dispersed CuSO4 and remaining isolated Cu2+ determined the low-temperature SCR behavior of the sulfur-poisoned catalysts.

The extinction peak of Pd particles generally locates at the ultraviolet light region, suggesting that only 4% of solar light can be absorbed. Furthermore, the efficiency of LSPR hot electrons converted to chemical energy of reaction is very low due to the fast relaxation of carriers. It is extremely valuable to design Pd-based catalysts which have strong response to the visible light irradiation and high efficiency in photon to chemical energy. The Pd–CeO2 catalyst was synthesized via the hexadecyltrimethylammonium bromide (CTAB) assisted liquid-phase reduction method to generate more active interfaces. The significant extinction of Pd–CeO2 in the visible to near-infrared region indicates the strong electron interaction between Pd and CeO2. LSPR hot electrons, transferring from the Pd metal particles to the conduction band of ceria, promote the dissociation of adsorbed oxygen. Therefore, the reaction temperature of CO and toluene oxidation can be significantly lowered by visible light irradiation. The ma...

A NbOx/Ce0.75Zr0.25O2 (NbCZ) catalyst was synthesized by a citric acid-aided sol-gel method. It shows that above 80% NOx conversion and above 95% N-2 selectivity for the selective catalytic reduction of NOx by ammonia over this catalyst are achieved in the temperature range 200-450 degrees C. Based on the DRIFTS and kinetic studies over NbCZ and Ce0.75Zr0.25O2, the promotion mechanism by niobia loading was elucidated with an overall reaction pathway. Two different reaction routes, "L-H" mechanism via "NH4NO3 + NO" at low temperatures ( 350 degrees C), are presented. The niobia addition increases the surface acidity and promotes the formation of nitrates species at low temperatures. In this way, the reaction between the ads-NH3 and nitrates species is accelerated to form NH4NO3 intermediates, which then decompose to N-2 and H2O. The reaction of the ads-NH3 species with gaseous NOx at high temperatures is also promoted due to the enhanced acidity and weakened thermal stability of nitrates after niobia loading.

Au nanoparticles and reduced graphene oxide (r-GO) co-modified TiO 2 nanotube arrays (TNTs) were prepared by a facile and green strategy based on the electro-deposition technology for detecting H 2 O 2 , O 2 and nitrite. As-prepared Au/r-GO/TNTs electrode was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results clearly demonstrate that the successful attachment of r-GO sheets and narrow-range distribution of Au nanoparticles on TNTs. The reduced grapheme oxide sheet can help to improve the electronic conductive performance of TNTs and prevent the agglomeration of Au nanoparticles. Electrochemical studies reveal that the Au/r-GO/TNTs electrode exhibit excellent electrocatalytic performance toward the reduction of H 2 O 2 . Under the optimal experimental condition, the sensor has a quick response to H 2 O 2 at −0.3 V with a high sensitivity (1011.35 mA M −1 cm −2 ), wide linear range (0.01–22.3 mM) and low detection limit (0.006 μM). In addition, the sensor also has good stability and excellent selectivity. Moreover, the established Au/r-GO/TNTs electrode also shows high sensitivities towards dissolved O 2 and nitrite ions, which has great potential for the development of electrochemical sensors, molecular bioelectronics devices and biosensors.

V 2 O 5 /WO 3 -TiO 2 and V 2 O 5 /WO 3 -TiO 2 -SiO 2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750 ℃ in 10 vol% H 2 O/air for 24 h. The catalysts were evaluated for NO x conversion using NH 3 as the reductant. Hydrothermal ageing decreased the NO x conversion of V 2 O 5 /WO 3 -TiO 2 catalyst severely over the entire measured temperature range. Interestingly, the NH 3 -SCR activity of the silica-modified catalyst at 220-480 ℃ is enhanced after ageing. The catalysts were characterized by X-ray diffraction, nitrogen adsorption, X-ray fluorescence, Raman spectroscopy, H 2 temperature-programmed reduction, and NH 3 temperature-programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO 2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V 2 O 5 /WO 3 -TiO 2 catalyst was significantly improved.

As oxygen is one of the essential reactants in the standard SCR reactions, the ability of restoring and releasing oxygen is an important factor to determine the SCR activity of the catalyst. Ceria catalysts present an innate prospect in SCR reaction because of the facilitated redox cycles from Ce4+ to Ce3+. In the present study, zirconium phosphate @ Ce0.75Z0.25O2 (ZP/CZ) catalysts were pre-treated by O2, N2 and H2 to study the effects of lean-oxygen teatment on the structure, NH3/NOx adsorption and activity of catalysts. The catalysts were characterized by activity test, H2-TPR, XPS, DRIFT, NOx-TPD and kinetics study. The results showed that H2 treatment led to deeply reduced catalyst surface, resulting in mainly nitrites instead of nitrates adsorbed on catalyst in NO + O2 reaction and reduced Bronsted acidity of catalyst, which were responsible for the lowered deNOx activity of H2 treated catalyst. N2 treatment had only negligible influence on catalyst compared to O2 treated catalyst. Ammonium nitrate route was consolidated as possible NH3-SCR reaction mechanism over ZP/CZ catalyst by kinetics study.

Cu-SAPO-34 selective catalytic reduction (SCR) catalyst deactivates upon exposure to water vapor at temperatures lower than 100 °C, which deteriorates its application prospects. The deactivation under cycled aging-regeneration conditions can be categorized into two stages, namely reversible and irreversible deactivation. Based on SCR reaction tests, and characterizations with diffuse reflection infrared Fourier transform spectroscopy (DRIFTS), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR), it is concluded that the transformation of active isolated Cu(II) ions to Cu(OH)2 is critical to both types of deactivation. Within the frame of reversible deactivation, Cu(OH)2 can be converted back to SCR active Cu(II) ions by interacting with Bronsted acid sites during high-temperature regeneration. However, interactions between Cu(OH)2 and hydrolyzed framework Al lead to the formation of CuAl2O4-like species, causing permanent loss of active Cu(II) ions and thus, irreversible deactivation.

The mullite SmMn2O5 (SMO) was modified with silver for soot oxidation by two methods, i.e. sol-gel (Ag/SMO-sg) and impregnation (Ag/SMO-im). The catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectrometry (ICP-AES), H2-O2 titration, H2 temperature-programmed reduction (H2-TPR), CO temperature-programmed reduction (CO-TPR), soot temperature-programmed reduction (soot-TPR), O2 temperature-programmed desorption (O2-TPD), cycled H2 temperature-programmed reduction (cycled H2-TPR), NO temperature-programmed oxidation (NO-TPO) and soot temperature-programmed oxidation (soot-TPO). Metallic silver nanoparticles were observed in the mullite matrix for both the catalysts. For Ag/SMO-sg, the possible incorporation of silver into the mullite crystal cell and strong electronic interaction between the highly dispersed metal and the support increase the Mn4+/Mn3+ ratio and create more structural defects in the mullite, resulting in boosted NO oxidation and thereby NO2-assisted soot combustion. The introduction of Ag can promote the generation/regeneration of active oxygen, which accelerates the ignition of soot in O2 at low temperatures. Therefore, the sol-gel-synthesized Ag/SmMn2O5 is highly promising for application in diesel particulate filters.

To investigate possible relationships between copper speciation and Bronsted acidity evolution during hydrothermal aging, a series of aged Cu-SSZ-13 catalysts were prepared by varying aging temperatures from 550 to 850 °C. Besides selective catalytic reduction of NOx by NH3 (NH3-SCR), NH3 oxidation was also adopted as a probe reaction. The catalysts were characterized by H2 temperature-programmed reduction (H2-TPR), in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and magic angle spinning nuclear magnetic resonance (MAS NMR). Isolated Cu ions protect Si-O(H)-Al sites against hydrothermal cleavage, but aggregated Cu species are found to destroy the zeolite framework. Due to the instability of ZCuOH (Z represents negatively charged zeolite [Si-O-Al]– site) at 8-member ring sites, mild hydrothermal aging induces the migration of metastable [Cu(OH)]+ ions to unsaturated 6-member ring sites to form Z2Cu, and excess [Cu(OH)]+ ions start to aggregate at 700 °C. The formation of two types of aggregated Cu species, CuAlOx and CuOx, and their roles in SCR reaction were distinguished. The former one originates from the combination of Cu with extraframework Al and is inert, while the latter forms upon more severe aging and catalyzes over-oxidation of NH3 toward NO, which degrades high-temperature SCR activity.

Cu-SSZ-13, as an efficient catalyst for NOx removal, has been commercialized in diesel exhaust aftertreatments. However, SCR catalysts in practical applications may suffer from alkali deactivation due to the introduction of engine oil additives and biodiesel. In this study, the poisoning effect of different potassium salts (K2CO3, K2SO4 and K3PO4) on the Cu-SSZ-13 catalyst was systematically investigated. Deactivation effect of potassium salts follows the order of K2CO3 > K2SO4 > K3PO4, resulting from the transformation of isolated Cu2+ into other copper species. The loss of isolated Cu2+ is considered as the main reason for the low-temperature deactivation while the formed copper oxides, copper sulfate and copper phosphate related species are mainly responsible for the different catalytic behaviors of the poisoned catalysts at high temperatures (>400 °C). The CuOx clusters induced by K2CO3 promote NH3 oxidation while the copper salts derived from K2SO4 and K3PO4 are relative inactive for this competitive reaction. As a balance between the consumption of NH3 by the side reaction and loss of Bronsted acid sites, the K2CO3 poisoned catalyst shows significantly dropped high-temperature SCR activity, while the reaction is promoted over those catalysts impregnated with K2SO4 and K3PO4 at high temperatures.

Multilayer graphene capsuled sulfur nanoparticles were successfully prepared by adsorption of the sulfur vapor on amorphous activated carbon (AC) at 700 °C. The samples were characterized by BET, SEM, TEM, XPS, FTIR, Raman and Zeta-potential testing measurements and adsorption tests. The results demonstrated that most of the elemental sulfur nanoparticles were in size of 22 nm and located in the mesopores of the graphitized AC. The sulfur nanoparticles were strongly interacting with neighboring carbons by forming –C–S– and –C–SOx– bonds. The adsorption capacities of the multilayer graphene capsuled sulfur nanoparticles were 785 mg g−1 for methylene blue and 49 mg g−1 for Cd2+ ions, which showed two times higher Cd2+ adsorption capacity but similar methene blue adsorption capacity compared with the pristine amorphous AC, although the BET surface area and pore volume of AC decreased significantly by sulfur modification. Cd2+ ions mainly chemically adsorbed on sulfur species which did not influence the adsorption capacity of small organics molecules, such as methene blue, in the micropores of AC. The method in this work provides a facile way to prepare a promising metal-free adsorbent for water treatment.

Selective catalytic reduction (SCR) with urea catalyzed by Cu-SAPO-34 is an effective method to eliminate NOx from diesel exhaust. However, urea-related deposits may form during cold-start and urban driving due to low exhaust temperatures. The activity of Cu-SAPO-34 at 175°C is significantly degraded by urea exposure, and 300°C is required for regeneration. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed hydrolysis studies, the dominant stable deposit at 175°C is identified as biuret, which can be eliminated at 300°C. The urea-derived deactivation and regeneration mechanisms of Cu-SAPO-34 were compared with those of anatase-supported catalysts.

A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species.