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Summary Ammonia synthesis is structure sensitive, and a minute change in the catalyst structure would cause a dramatic change in activity. To date, none of the studies reveal the metal size effect at a subnanometer scale on NH3 synthesis, and such investigation remains a challenge. Here, we report the synthesis of Ru catalysts with sizes ranging from single atoms, atomic clusters (ACCs), sub-nanometric clusters, to nanoparticles (NPs) by adjusting precursor and/or loading of Ru. Sub-nanometric Ru catalysts not only exhibit performance different from that of NPs but also follow a different route for N2 activation. The strong intra-cluster interaction of Ru atomic clusters enables the formation of strong interactions of Ru d-orbitals with the σ and π orbitals of N2 molecules, resulting in N2 activation over Ru ACCs to occur more easily than that over Ru NPs. Consequently, Ru ACCs display an unprecedentedly high NH3 synthesis rate and large turnover frequency at mild conditions.

Identifying optimal Ru size in NH3 synthesis can improve reaction activity and maximize the utilization of Ru to reduce catalyst cost. However, previous researches are focused on large Ru particle size (≥ 2 nm) while that below 2 nm in NH3 synthesis is unclear. Here we synthesized a series of Rux/BaCeO3 with different Ru sizes (x=1.1–3.0 nm) through size-controlled Ru colloid. With the decrease of Ru size, NH3 synthesis rate over Ru1.1/BaCeO3 increases to 19.4 mmol gcat−1 h−1 at 400°C and 1 MPa, which is 5.7 times that of Ru3.0/BaCeO3 and superior to most of Ru-based catalysts previously reported. It reveals that the reduction of Ru size enhances the generation of Ce3+ and oxygen vacancies in BaCeO3, which can donate electron to Ru centers and promote N2 dissociation. Moreover, the small Ru size enhances hydrogen spillover from Ru to BaCeO3 to alleviate hydrogen poisoning, resulting in efficient NH3 synthesis.

Gemcitabine (GEM) is the first-line medication for pancreatic ductal adenocarcinoma (PDAC). However, over some treatment cycles, GEM sensitivity declines and chemotherapeutic resistance develops, resulting in tumor recurrence and metastasis. Therefore, it is critical to elucidate the mechanism of GEM chemoresistance. And a specific drug that is closely related to the mechanism is urgently required to sensitize GEM. Here, tissue inhibitor of matrix metalloproteinases 1 (TIMP1) and phosphorylated mammalian target of rapamycin (p-mTOR) were found to be substantially elevated in PDAC patients and were associated with worse overall survival. The TIMP1/PI3K/AKT/mTOR pathway was found in GEM-resistant PDAC cells and was revealed to be involved in epithelial-mesenchymal transition (EMT) and apoptosis. Furthermore, arsenic trioxide (ATO), a basic therapeutic drug for acute promyelocytic leukemia, mediated TIMP1 reduction by inducing reactive oxygen species generation and hampered the subsequent PI3K/AKT/mTOR axis. Moreover, the combination of ATO and GEM cooperatively suppressed the TIMP1/PI3K/AKT/mTOR pathway, synergistically inhibited EMT and promoted apoptosis. In vitro and in vivo, ATO combined with GEM has a collaborative anticancer effect, inhibiting cancer cell proliferation, migration, invasion, and suppressing tumor growth both in PDAC parental and GEM-resistant cells. Overall, the TIMP1/PI3K/AKT/mTOR pathway is present in PDAC and linked to GEM resistance. ATO suppresses the axis to sensitize GEM and reverse GEM resistance, suggesting a promising treatment for the disease.

Perineural invasion (PNI) occurs in most pancreatic ductal adenocarcinomas (PDACs). The relationship between cancer cells and peripheral nerves, however, is unknown. Therefore, we focused on the cooperation of PDAC cells and peripheral nerve astrocytes, Schwann cells (SCs), in PNI. The mutual tumor-supportive secretory cytokines between SCs (sNF96.2) and PDAC cells (PANC-1, BxPC-3) were screened by human cytokine arrays and verified. The prognostic value of selected cytokines and SC-associated markers was confirmed in PDAC patients. TIMP1 and CCL7 were found to form a paracrine feedback loop between PDAC cells and SCs. PDAC cell-derived TIMP1 promotes SCs proliferation and migration via CD63/PI3K/AKT signaling. CCL7 secreted from SCs enhances PDAC cell migration, invasion and expression of TIMP1 via CCR2/STAT3. PDAC cell-SC cooperation in PNI was blocked when TIMP1 knockdown in vitro and in vivo. Finally, TIMP1, CCL7 and SC-associated markers were correlated with PNI and prognosis in PDAC patients. In conclusion, SCs collaborate with PDAC cells through the TIMP1-CCL7 paracrine feedback loop to promote PNI. TIMP1 knockdown in PDAC cells suppresses PNI. Strategies to disrupt the TIMP1-CCL7 feedback loop might be developed to inhibit PNI in PDAC.

It is known that a highly dynamic communication among subcellular organelles (e.g., cytosol, endoplasmic reticulum (ER), mitochondria, and nucleus) dictate cellular behaviors. But little information exists on how the inter-organelle crosstalk impacts cancer cells due to the lack of approaches that manipulate inter-organelle communication in cancer cells. We unexpectedly found that a negatively charged, enzyme cleavable peptide enables the trafficking of histone protein (H2B), a nuclear protein, to the mitochondria in cancer cells. The peptide, denoted as MitoFlag, interacts with the nuclear location sequence (NLS) of H2B to block it entering nucleus. A protease on the mitochondria cleaves the Flag from the complex of MitoFlag and H2B to form assemblies that retain H2B on the mitochondria and facilitate the H2B entering mitochondria. Molecular validation of MitoFlag shows that adding NLS, replacing aspartic acid residues by glutamic acid residues, or changing L-aspartic acid to D-aspartic residue abolishes the trafficking of H2B into mitochondria of HeLa cells. As the first example of enzyme-instructed self-assembly (EISA) of a synthetic peptide for trafficking endogenous proteins, this work provides insights for understanding and manipulating inter-organelle communication in cells.

Two precursors, namely, p-CFO-T (tetragonal) and p-CFO-C (cubic), were fabricated by a sol-gel method via citric acid and poly(vinyl alcohol) complexation, respectively. After H2-reduction, the two were converted to Cu/Fe3O4 catalysts of different complexions, which are named as CFO-CA and CFO-PVA, respectively. The distribution of Fe2+ and Fe3+ in the Cu/Fe3O4 catalysts was studied by Raman and XPS techniques. It was disclosed that the distribution of Fe2+ and Fe3+ in Fe3O4 has an effect on Cu–Fe3O4 interaction and catalyst surface basicity. Compared to CFO-PVA, CFO-CA has a larger amount of Fe3+, which mostly sits at the octahedral sites, leading to stronger Cu–Fe3O4 interaction, and a larger amount of catalyst surface sites that are of weak basicity. As a result, the critical elementary steps of WGS reaction, viz. water dissociation, –COOH decomposition and CO2 desorption are promoted as reflected in the lower Ea and higher catalytic activity of CFO-CA.

A series of CoMgAl mixed oxides with homogeneous Co dispersion were prepared using co-precipitation method. The CoMgAl composites were then doped with Mo species, giving Mo/Co(x)MgAl (x=Co/(Co+Mg)) catalysts for water-gas shift reaction (WGSR). In the synthesis of these catalysts, there is limited release of ammonia, which is traditionally common in the generation of Mo-Co catalysts for WGSR. The Mo/Co(x)MgAl catalysts were characterized using techniques such as XRD, N2-physisorption, H2-TPR, H2S-TPS, Raman, HRTEM and XPS. It is noted that the Mo/Co(5%)MgAl catalyst gives 91.2% CO conversion at 350 °C, which is close to the equilibrium CO conversion (91.7%). The H2S-TPS results disclose that there is decrease in activation energy for Mo sulfidation with increase of Co content in Mo/Co(x)MgAl, indicating the presence of Co promotes Mo sulfidation. The outcomes of HRTEM and XPS analyses reveal that the role of Co is to decrease stacking number and slab length of MoS2 moieties. The EDX elemental analysis suggests synergism between Co and MoS2, especially in the case of Mo/Co(5%)MgAl. With the formation of small-size MoS2 slabs and enhanced Co-MoS2 synergistic effect, the Mo/Co(5%)MgAl catalyst has high exposure of active sites, leading to improved catalytic activities in WGSR.

The alloying of Ru with rare-earth elements (REEs) is an effective approach for the modification of the electronic structure of Ru. Here, for the first time, we report the formation of Ru-M (M=La or Y) alloys that are endowed with a completely new type of active sites. Over the Ru-M (M=La or Y) catalysts, N2 activation in ammonia synthesis follows neither the well-known dissociative nor the associative route but rather a co-operation of both, leading to outstanding performance. The developed RuLa/HZ catalyst exhibits a NH3 synthesis rate of 14.73 mmol gcat−1 h−1 at 400 °C and 1 MPa without obvious deactivation in a run of 1756 h (ca.73 days).

CuO/CeO2 is a kind of promising catalysts for the water-gas shift (WGS) reaction. Efforts were put in to improve its performance through modification of CeO2 support. In this study, portions of CeO2 prepared by a co-precipitation method were separately annealed at 300 °C in air, under vacuum and with H2 , and were used as supports for the fabrication of CuO/CeO2 catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N2 -physisorption, inductively coupled plasma, Raman spectroscopy, CO2 temperature-programmed desorption, and H2 temperature-programmed reduction techniques. The relation between catalytic performances and physicochemical properties of the CuO/CeO2 catalysts were discussed. Among the three catalysts, the one with CuO supported on H2 -reduced CeO2 shows the highest catalytic activity, mainly due to strong CuO-CeO2 synergetic interaction and high concentration of Frenkel-type oxygen vacancies. The superior catalytic activities can also be attributed to the Cu0 crystals of small size and the oxygen vacancies in non-stoichiometric CeO2-x .

A series of Mg-Al-Ce mixed oxides with (nMg2+)/(nCe3+ + nAl3+) = 5 and nCe3+/(nCe3+ + nAl3+) = 0 ∼ 7% were synthesized by co-precipitation method based on a hydrotalcite route and used as support to prepare Co-Mo sulfur-resistant water-gas shift (WGS) catalysts. The supports and catalysts were characterized by XRD, ICP, N2-physisorption, CO2-TPD, H2-TPR, H2S-TPS, TEM, and CO-IR. It is found that the catalytic performance and physicochemical property of the Co-Mo/Mg(Al)O catalyst are significantly influenced by the Ce modification. The addition of Ce effectively enhances the WGS activity and the highest activity is obtained on the Co-Mo/Mg(Al)O-CeO2 (5%) catalyst, where the activity at 623 K increases about 2.5 times. The results of H2S-TPS investigation show that in the presence of Ce, the H2S consumption peak shifts to lower temperatures and there is decrease of Mo sulfidation activation energy. Furthermore, HRTEM analysis shows that the addition of Ce (5%) results in decrease of MoS2 slab length and stacking number, and those of CO-IR characterization indicate increased exposure of surface MoS2 sites. It is suggested that the addition of Ce promotes the formation of MoS2 slabs that are smaller in size, leading to higher exposure of surface active sites and hence higher activity.

Rare earth element (La, Y, and Ce) modified MgAl-hydrotalcites of MgAlM were synthesized from coprecipitation and calcination, and further loaded with CoMo active species to give CoMo/MgAlM catalysts. X-ray powder diffraction, inductively coupled plasma, and N2 adsorption isotherms indicate that MgAlM possess large BET surface areas (58–91 m2/g), and rare earth elements were successfully introduced into samples. CO2-TPD (temperature-programmed desorption), NH3-TPD, H2-TPR (temperature-programmed reduction), H2S-TPS (temperature-programmed sulfidation), and Raman spectra indicate the presence of unique interactions between rare earth elements and Mo active species, which strongly affect the reduction and sulfidation behaviors of these catalysts. High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analysis suggest that the addition of rare earth elements decreases the slab length and stacking numbers of MoS2 and promotes the sulfidation degree of Mo oxides. Th...

Hydrotalcite-like compounds (HTlcs) are promising supports or catalyst precursors for heterogeneous catalysts. Herein, MgAl-HTlcs-supported Pd catalyst was fabricated, and two Pd catalysts supported on Mg(OH)2 and Al(OH)3 were prepared for comparison. The presence of hydroxyl groups (OH-) in the support is important for obtaining uniform Pd nanoparticles with small sizes. We found that Pdn+ species are more active than Pd0 in low temperature CO oxidation due to their lower barrier in CO activation. The Pd/MgAl-HT catalyst shows the most stable Pdn+ at a temperature lower than 90 °C, leading to the highest catalytic activity towards CO oxidation. Pdn+ in the Pd/Al(OH)3 catalyst is more stable than that in Pd/Mg(OH)2 at low temperature, which is ascribed to its smaller temperature hysteresis (Thysteresis) between the oxidation and re-reduction cycles. The effect of hydroxyl groups on stabilizing Pd species is related to the stability of Pd catalyst in CO oxidation reaction.

In this paper, CoMo supported on Nb modified MgAl mixed oxide by calcination of layered double hydroxides (LDHs) were prepared using wet impregnation method. The fresh calcined catalysts were further sulfided by H 2 S/H 2 and tested for water-gas shift reaction (WGSR). The physicochemical properties of fresh calcined catalysts were characterized by various adsorption and bulk techniques like XRD, ICP, N 2 -physisorption, CO 2 -TPD, H 2 -TPR, H 2 S-TPS and HRTEM. It is found that the addition of Nb does not affect the formation of LDHs, but changes the reduction and sulfidation behavior of Mo species on oxidic catalyst as well as the dispersion of MoS 2 phase on the sulfided catalyst. The CoMo/Nb(5%)MgAl catalyst shows the lowest apparent sulfidation activation energy, consumes the highest amount of H 2 S and thus has the highest catalytic activity in WGS reaction.

Ru catalysts (2 wt%) supported on Mg and/or Al oxides including γ-Al 2 O 3 , MgAl 2 O 4 , Mg 3 (Al)O, and MgO were prepared by incipient wetness impregnation and compared for the CH 4 -CO 2 reforming to investigate the effect of support on the Ru dispersion and catalytic performance. The catalysts before and after reaction were well characterized by using N 2 physical adsorption, ICP, SEM-EDX, XRD, H 2 -TPR, TEM, CO chemisorption, FTIR of CO adsorption, XPS, CO 2 -TPD, TG, and Raman spectroscopy. The characterization results revealed that Ru metal was very highly dispersed on the Mg 3 (Al)O mixed oxide obtained from Mg-Al layered double hydroxide, probably existing in very small nanoparticles and/or clusters. The order of Ru metal dispersion was Ru/Mg 3 (Al)O > Ru/MgO > Ru/MgAl 2 O 4 > Ru/γ-Al 2 O 3 . The catalytic activity and stability of the Ru catalysts were greatly dependent on the support. Both Ru/MgO and Ru/Mg 3 (Al)O showed higher activity than Ru/MgAl 2 O 4 and Ru/γ-Al 2 O 3 , which might be related to the strong base intensity of support and more accessible surface Ru 0 atoms, respectively. During 30 h of reaction at 1023 K, a significant deactivation occurred on Ru/γ-Al 2 O 3 , Ru/MgAl 2 O 4 , and Ru/MgO, which was mainly attributed to the sintering of Ru metal particles. In contrast, the Ru/Mg 3 (Al)O catalyst exhibited superior stability and no significant sintering of Ru metal was observed, suggesting that the highly dispersed Ru metal was stable. A 300 h long-term test further demonstrated the excellent stability of Ru/Mg 3 (Al)O. These results highlight the significant effect of Mg(Al)O mixed oxide on the improvement of Ru dispersion and catalytic performance, and this might be related to the unique properties of Mg(Al)O mixed oxide including memory effect, low crystallinity, and its strong interaction with Ru.

Mg(Al)O mixed metal oxide (MMO) supported Cu nanoparticles catalysts have been prepared by calcination and reduction of Cu-Mg-Al layered double hydroxides (LDHs). By adjusting the chemical compositions of LDHs precursors, various catalysts with 10–40 wt% Cu content and molar ratio of (Cu + Mg)/Al = 1–4 were prepared. The catalysts were characterized by ICP, N 2 physical adsorption, XRD, TEM, H 2 -TPR, and N 2 O chemisorption, and tested for the water-gas shift (WGS) reaction. The characterization results suggested that upon calcination Cu-Mg-Al LDHs were converted to Mg(Cu, Al)O MMOs, where both Cu 2+ and Al 3+ were incorporated into the MgO framework to form a solid solution; reduction of Mg(Cu, Al)O gave highly dispersed and uniform Cu metal nanoparticles. The Cu metal dispersion was as high as 22–78% and the particle size varied from 1.5 to 5 nm depending on the chemical compositions. The WGS activity of the Cu catalysts increased with the increase of Cu 0 surface area. Among the prepared catalysts, the 30%Cu/Mg 2 Al catalyst exhibited the highest Cu surface area and the highest WGS activity. The optimized catalyst also showed superior activity, thermal stability, and steady-state stability than a commercial Cu/ZnO/Al 2 O 3 catalyst under the present reaction conditions. The characterization on the spent catalysts showed that the LDHs-derived Cu nanoparticles remained highly dispersed, suggesting that the Mg(Al)O supported Cu nanoparticles were stable and possessed good resistance against sintering.

Hydrotalcite-like compounds (HTlcs) are promising supports or catalyst precursors for heterogeneous catalysts. Herein, MgAl-HTlcs-supported Pd catalyst was fabricated, and two Pd catalysts supported on Mg(OH)2 and Al(OH)3 were prepared for comparison. The presence of hydroxyl groups (OH-) in the support is important for obtaining uniform Pd nanoparticles with small sizes. We found that Pdn+ species are more active than Pd0 in low temperature CO oxidation due to their lower barrier in CO activation. The Pd/MgAl-HT catalyst shows the most stable Pdn+ at a temperature lower than 90 °C, leading to the highest catalytic activity towards CO oxidation. Pdn+ in the Pd/Al(OH)3 catalyst is more stable than that in Pd/Mg(OH)2 at low temperature, which is ascribed to its smaller temperature hysteresis (Thysteresis) between the oxidation and re-reduction cycles. The effect of hydroxyl groups on stabilizing Pd species is related to the stability of Pd catalyst in CO oxidation reaction.

CuO/CeO

The water-gas shift reaction is studied using a series of Cu–Fe composite oxide catalysts, which were prepared by co-precipitation, deposition-precipitation, sol–gel, solid state reaction and mechanical mixing method, respectively. Distinct crystal structure and texture of the as-prepared catalysts were formed, and their reduction properties as well as surface basicities were modulated. The CO conversion in the water gas shift reaction is found to be correlation well with the Cu components in the temperature range of 200–350 °C, while the CO conversion is mainly controlled by Fe3O4 sites at temperature above 350 °C. The characterization results demonstrate that the formation of CuFe2O4 is ideal to obtain well dispersed Cu crystals; the weak basic sites are positive to the WGS reaction; and the strong interaction between copper and iron species can result in good Cu dispersion. The catalyst that was fabricated by the co-precipitation method, possesses the largest amount of CuFe2O4 and weak basic sites, as well as highly dispersed Cu crystals, thus showing the best catalytic activity and stability for the WGS reaction in our cases.

The precipitation processes of CuO–CeO2 catalysts preparation were modified, and their optimized copper content were also studied in detail. As indicated by the experimental results, the WGS catalytic activities of the CuO–CeO2 catalysts can be ranked as: stepwise precipitation (SP) > deposition–precipitation (DP) > co-precipitation (CP), suggesting that stepwise precipitation (i.e., a modified DP) is a convenient and effective method to prepare CuO–CeO2 WGS catalysts. The optimized copper contents of CuO–CeO2–SP and CuO–CeO2–CP catalysts are 20 wt.% and 25 wt.%, respectively. Their catalytic activities can be strongly correlated with the results from XRD, XPS, Raman, N2-physisorption, N2O chemisorption and H2-TPR. For DP and SP, a certain amount of copper has substitutively incorporated into ceria lattice with multiple Ce3+ and oxygen vacancies, which is considered as one relatively strong interaction between copper and ceria support. The substitutional incorporation of copper creates larger lattice distortion, lattice defect (embodying as larger lattice cell contraction of CeO2, microstrain and Raman shift) and stronger reducibility (i.e., lower reduction temperature of H2-TPR), as a consequence, higher surface energy and catalytic activity for WGS reaction. While for CP, copper nitrate and cerium nitrate were simultaneously precipitated, resulting in the burial of many copper species in ceria supports, i.e., occupancy incorporation of isolated copper into ceria lattice vacant site, which is considered as another weak interaction between copper and ceria support. Accordingly, combined with N2O chemisorption results, it is demonstrated that surface copper species of CuO–CeO2–CP are fewer and less active than those of CuO–CeO2–DP and CuO–CeO2–SP. Lastly, there is a direct relationship between the pore volume along with most probable pore size of the as-synthesized catalysts and their corresponding catalytic activities for WGS reaction.

The catalytic properties of ZnO-modified copper ferrite in water-gas shift (WGS) reaction were evaluated between 250 and 400°C. The Zn2.5-Cu/Fe (modified by 2.5% ZnO) showed high catalytic activity. The catalyst was characterized with XRD, SEM, H2-TPR and CO2-TPD techniques and N2 sorption experiment. It was shown that introduction of appropriate amounts of ZnO transformed the CuFe2O4 from the tetrahedral crystalline phase to the cubic, enhanced the CuFe2O4 reducibility, and increased the amount of weak and medium basic sites. As a consequence, the interaction between copper and iron species was improved and the catalytic activity was increased.

Three kinds of CuFe 2 O 4 catalysts were synthesized by co-precipitation method using potassium hydroxide (A), sodium carbonate (B) and sodium bicarbonate (C) as the precipitants. Their catalytic activity and thermal stability were evaluated in water-gas shift reaction (WGSR). The microstructure and surface property of as-prepared catalysts was investigated by X-ray diffraction (XRD), N 2 -physisorption, H 2 -temperature programmed reduction (H 2 -TPR), CO 2 -temperature programmed desorption (CO 2 -TPD) and cyclic voltammetry (CV). The results show that the catalyst prepared with potassium hydroxide as precipitant exhibits excellent WGSR activity. Potassium hydroxide plays an important role in promoting the generation of CuFe 2 O 4 , restraining growth of crystalline CuO and CuFe 2 O 4 , resulting in much better dispersion of CuO on the surface of catalysts, enhancing the reducibility of catalysts, and increasing the amount of weak basic sites. These factors remarkably improve the activity and thermal stability of catalysts.

A series of copper ferrite-based catalysts were prepared by the co-precipitation method using KOH, K 2 CO 3 , Na 2 CO 3 , NaOH, and NaHCO 3 as the precipitants and their physicochemical properties were investigated by N 2 -physisorption, SEM, XRD, FT-IR, Raman, H 2 -TPR, N 2 O decomposition, and CO 2 -TPD. The characterization results indicated that the utilization of KOH as precipitant was favorable for the formation of copper ferrite, which exhibited smaller crystalline and higher reducibility. The catalytic test in the water–gas shift reaction (WGSR) revealed that the sample prepared with the KOH as precipitant exhibited higher activity and thermal stability than the other samples. It was suggested that higher Cu dispersion, larger amount of surface copper atoms, weak basic sites, and strong interaction between copper and iron oxides resulting from the copper ferrite were responsible for the high catalytic performance.

A novel configuration of porous ZnO/Sn1−xZnxO2−x heterojunction nanocatalyst with high photocatalytic activity was successfully synthesized through a simple two-step solvothermal method. Porous Sn1−xZnxO2−x was synthesized from Zn2+ and Sn4+ precursors with the Zn/Sn ratio of 2:1 in the absence of alkali, and then intermolecular dehydrolysis led to the formation of heterointerface between Sn1−xZnxO2−x and ZnO. The results show that Zn2+ doping exhibits a significant influence on particle size of SnO2 leading to much higher specific surface area and larger band gap, which is in favor of the photocatalytic activity of SnO2 under UV light irradiation. In addition, the formation of ZnO/Sn1−xZnxO2−x heterostructure improves the separation of photogenerated electron–hole pairs due to the potential difference between Sn1−xZnxO2−x and ZnO, which also benefits to photocatalysis. By taking account of them together, these results provide further insight into the synergistic effects of metal ion doping and semiconductor/semiconductor heterostructure on the activity of photocatalysts in environmental remediation applications.

A series of CuO/ZrO 2 catalysts with different Cu loadings (4.1, 6.1 and 8.4 wt.%) were synthesized by a deposition-precipitation method and evaluated with the water–gas shift (WGS) reaction. In order to distinguish the different supported copper oxide species, (NH 4 ) 2 CO 3 -leaching process was conducted on the three CuO/ZrO 2 catalysts. The parent and leached catalysts were characterized by ICP-OES, XPS, XRD, N 2 -physisorption, N 2 O titration, UV–Vis DRS, H 2 -TPR and CO-TPR. The results reveal that three types of copper oxide species are present on the parent CuO/ZrO 2 catalysts: (α) highly dispersed CuO that is weakly bound with ZrO 2 ; (β) strongly bound Cu-[O]-Zr species, which can not be leached by (NH 4 ) 2 CO 3 solution and is possibly associated with the surface oxygen vacancy of ZrO 2 ; (γ) crystalline CuO. The XRD and TEM results of the freshly reduced catalysts disclose that the three types of CuO species are transformed into their corresponding metallic states after the H 2 -pretreatment. It is found that the reaction rate correlates well with the amount of Cu-[O]-Zr species, indicating the metallic Cu derived from this species should be the catalytically active copper species for the WGS reaction. Moreover, CO-TPR results disclose that the Cu-[O]-Zr species play a significant role in promoting the reactivity of the surface hydroxyl groups, as is thought to be responsible for the high WGS activity of the CuO/ZrO 2 catalysts.

Three Cu/ZrO2 catalysts were synthesized utilizing co-precipitation (CP), deposition–precipitation (DP) and deposition–hydrothermal (DH) methods, respectively. The microstructure and texture of those catalysts are characterized by means of XRD, SEM, N2-physisorption, Raman and EPR characterizations. It is demonstrated that different morphologies and textures of ZrO2 are formed, and the micro- and crystal structure of Cu nanoparticles as well as the concentration of oxygen vacancies of ZrO2 are distinguish from each other. In addition, H2-TPR technique is employed to investigate the reducibility properties of the as-synthesized Cu/ZrO2 catalysts. It is found that the synergy interaction between Cu–ZrO2 obtained by the DH method is the strongest, owning to the possession of the largest amount of oxygen vacancies. Furthermore, their catalytic activities with respect to the water gas shift reaction are also performed, and the Cu/ZrO2-DH shows high catalytic activity, the reasons are the well dispersion and small crystallite size of Cu, the largest amount of oxygen vacancies, as well as the strongest interaction between Cu–ZrO2.

A series of CuO/CeO2 catalysts doping with Nb2O5 were fabricated by co-precipitation method. It is found that the introduction of Nb5+ will result in the substitution of Ce4+ with Nb5+, thus creating mobile electronic carriers in the as-prepared catalysts. The characterization results correlating with the catalytic activity evaluation disclose that the catalyst added with 1 wt. % Nb2O5 shows the most mobile electronic carries, certain amount of weak, medium basic sites and enhanced reducibility and chemical adsorption of CO, thus the best catalytic activity for water–gas shift reaction. However, excessive Nb2O5 addition prevents the incorporation of Cu2+ into CeO2 lattice and partially covers the surface of CuO and CeO2, resulting in weaken their reducibility and interaction between them, thus leading to inferior catalytic performance.

A series of Au/ZrO2 catalysts with low content of gold (

Au/ZrO2 catalysts with a nominal gold loading of 1.0% were prepared by a deposition-precipitation method employing a series of ZrO2 samples synthesized by a convenient hydrothermal route as supports. These catalysts were evaluated for low-temperature water-gas shift reaction under a model reformed methanol gas atmosphere. The effect of the hydrothermal synthesis temperature of zirconia on the catalytic activity of Au/ZrO2 was investigated. The optimal hydrothermal synthesis temperature of ZrO2 was 150 °C. The corresponding catalyst offers a CO conversion of 87% at a reaction temperature of 240 °C, which is significantly higher than that of the previously reported Au/Fe2O3, Au/CeO2, and Au/CeZrO4 catalysts. The Au/ZrO2 catalysts were characterized by X-ray diffraction, atomic absorption spectrometry, N2-physisorption, and scanning electron microscopy. The results indicate that the catalytic performance of the Au/ZrO2 catalysts is mainly influenced by the morphology and pore structure of the ZrO2 that was hydrothermally synthesized at different temperatures. A uniform nanodisk morphology and increase in the pore volume and pore diameter of the ZrO2 particles lead to a higher catalytic activity of the Au/ZrO2 catalyst.

The water-gas shift reaction was used to evaluate a series of La2O3 modified CuO/CeO2 catalysts that were prepared by a parallel co-precipitation method. The catalytic activity and thermal stability improved significantly upon the introduction of La2O3, and CuO/CeO2-La2O3 (2 wt%) gave the highest activity and had the best thermal stability. The microstructure of the as-prepared CuO/CeO2-La2O3 catalysts and/or the CeO2-La2O3 supports was characterized by X-ray diffraction, N2 physisorption, Raman spectroscopy, and temperature-programmed reduction. The results indicate that larger specific surface areas and smaller crystal sizes of CuO and CeO2 result in improved catalytic performance for the as-prepared catalysts. Moreover, the incorporation of La3+ into the ceria lattice promotes the generation of oxygen vacancies leading to a higher number of moderate copper oxides that interact with surface oxygen vacancies on the surface of the ceria. This enhances the activity and thermal stability of the CuO/CeO2 catalyst.

A series of CeO 2 supports were firstly prepared by precipitation method with NH 3 ⋅H 2 O (NH), (NH 4 ) 2 CO 3 (NC) and K 2 CO 3 (KC) as precipitant, respectively, and then CuO/CeO 2 catalysts were fabricated by depositing CuO on the as-obtained CeO 2 supports by deposition-precipitation method. The effect of CeO 2 supports prepared from different precipitants on the catalytic performance, physical and chemical properties of CuO/CeO 2 catalysts was investigated with the aid of XRD, N 2 -physisorption, N 2 O chemisorption, FT-IR, TG, H 2 -TPR, CO 2 -TPD and cyclic voltammetry (CV) characterizations. The CuO/CeO 2 catalysts were examined with respect to their catalytic performance for the water-gas shift reaction, and their catalytic activities and stabilities are ranked as: CuO/CeO 2 –NH > CuO/CeO 2 –NC > CuO/CeO 2 –KC. Correlating to the characteristic results, it is found that the CeO 2 support prepared by precipitation with NH 3 ⋅H 2 O as precipitant (i.e., CeO 2 –NH-300) has the best thermal stability and least surface “carbonate-like” species, which make the corresponding CuO/CeO 2 –NH catalyst presents the highest Cu-dispersion, the highest microstrain (i.e., the highest surface energy) of CuO, the strongest reducibility and the weakest basicity. While, the precipitants that contain CO 3 2- (e.g. (NH 4 ) 2 CO 3 and K 2 CO 3 ) result in more surface “carbonate-like” species of CeO 2 supports and CuO/CeO 2 catalysts. As a result, CuO/CeO 2 –NC and CuO/CeO 2 –KC catalysts present poor catalytic performance.

Copper supported on ceria prepared by the impregnation method was used as a model catalyst to investigate the synergetic mechanism between copper species and ceria for NO reduction by CO. To identify the copper species in the catalyst, we treated the as-synthesized Cu/CeO 2 by 30 wt.% nitric acid solution. Fresh and nitric acid treated Cu/CeO 2 catalysts were characterized and compared with AAS, XRD, TPR, EPR, Raman and NO-TPD techniques. It is found that, after nitric acid treatment, there is only 0.27 wt.% Cu left (vs. 5 wt.% Cu in fresh sample); this is present in the following forms: (1) isolated copper ions in octahedral sites of ceria, (2) copper oxide clusters and (3) copper ions in ceria lattice. The residual small amount of Cu has a significant effect on surface structure, redox property and catalytic behavior of ceria, indicating that these copper species are crucial copper species inducing copper–ceria interactions. Moreover, it is suggested that the relative free movement of oxygen from ceria to supported copper, caused by the three copper species, leads to oxygen vacancies in ceria, significantly enhancing the NO conversion of Cu/CeO 2 during NO + CO reaction.

Water–gas shift reaction was carried out over a series of CuO/CeO2 catalysts doped with trivalent rare earth oxide (RE2O3, RE = Y, La, Nd and Sm), prepared via co-precipitation method. The effect of the dopants on the structure and catalytic properties of CuO/CeO2 catalysts was investigated with the aid of X-ray diffraction (XRD), Raman spectra, N2 physisorption, H2-TPR and selective N2O chemisorption characterizations. The results reveal the beneficial role of La2O3 and Nd2O3 doping in increasing the WGS catalytic activities and stabilities of CuO/CeO2 catalysts, while the addition of Y2O3 and Sm2O3 leads to the negative effect. Correlating to the characteristic results, it is found that the performance of CuO/CeO2–RE2O3 catalysts strongly depends on their surface copper dispersion, microstrain value and the amount of oxygen vacancies generated in ceria lattice. Besides, enough evidences suggest that, the most effective active site for WGS reaction is the moderate copper oxide (crystalline) interacted with surface oxygen vacancies of ceria in the CuO–CeO2 system.

Copper supported on ceria and ceria-magnesia catalysts were synthesized and used for NO reduction by CO. The supports and the subsequent Cu catalysts were prepared by citric acid sol–gel and impregnation methods, respectively. Based on XRD, TPR and EPR measurements, it is found that the Mg addition promotes not only the dispersion of CuO, but also the doping of copper ions into CeO 2 matrix. A redox treatment favors some of copper ions in the octahedral sites of CeO 2 substituting the lattice sites of Ce 4+ . Combining the results of activity test, we found that the formation of copper-substituted Cu-O-Ce solid solution promotes the catalytic activity of the catalysts. Also, the ways that MgO acts on the dispersion of CuO and the formation of Cu-O-Ce solid solutions were investigated with the aid of TEM, TGA and XRD techniques. The results of these studies suggest that magnesia crystallites undergo a phase evolvement during the preparation process of Cu/MgO-CeO 2 , leading to the reconstitution of the support and hence the improvement of copper dispersion, BET surface area, pore volume, as well as the doping of copper ions into the CeO 2 matrix.

This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0–5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction (XRD), Raman spectroscopy, H2-TPR, cyclic voltammetry (CV) and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity (CO conversion reaches 93.4% at 250 °C) and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile (i.e., the reduction of surface copper oxide (crystalline forms) interacted with surface oxygen vacancies on ceria), and the area of peak C2 and A1 (Cu0↔Cu2+ in cyclic voltammetry process), respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.

A series of CuO/CeO2 catalysts were prepared through a two-step process: (1) CeO2 supports were firstly prepared by precipitation (P), hydrothermal (HT) and sol-gel (SG) methods, respectively; and (2) CuO was deposited on the above CeO2 supports by deposition-precipitation method. The as-synthesized CeO2 supports and CuO/CeO2 catalysts were characterized by N2-physisorption, XRD, XPS, Raman, and H2-TPR. The CuO/CeO2 catalysts were examined with respect to their catalytic activity for the water–gas shift reaction, and their catalytic activities are ranked as: CuO/CeO2-P > CuO/CeO2-HT > CuO/CeO2-SG. The results suggest that the CeO2 prepared by precipitation (i.e., CeO2-P-300) has the best thermal stability and the most amounts of surface oxygen vacancies, which make the corresponding CuO/CeO2-P catalyst present the largest pore volume, the smallest crystal size of CuO, the highest microstrain (i.e., the highest surface energy) and the most amounts of active sites (i.e., the moderate copper oxide (crystalline) interacted with surface oxygen vacancies of ceria). Therefore, the catalytic activity of CuO/CeO2 catalysts, in nature, depends on the thermal stability and the number of surface oxygen vacancies of the CeO2 supports previously prepared by different methods.

A network-structured SnO(2)/ZnO heterojunction nanocatalyst with high photocatalytic activity was successfully synthesized through a simple two-step solvothermal method. The as-synthesized samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, N(2) physical adsorption, and UV-vis spectroscopy. The results show that the SnO(2)/ZnO sample with a molar ratio of Sn/Zn = 1 is a mesoporous composite material composed of SnO(2) and ZnO. The photocatalytic activity of SnO(2)/ZnO heterojunction nanocatalysts for the degradation of methyl orange is much higher than those of solvothermally synthesized SnO(2) and ZnO samples, which can be attributed to the SnO(2)-ZnO heterojunction, the pore structure, and higher Brunauer-Emmett-Teller (BET) surface area of the sample: (1) The SnO(2)-ZnO heterojunction improves the separation of photogenerated electron-hole pairs due to the potential energy differences between SnO(2) and ZnO, thus enhancing the photocatalytic activity. (2) The SnO(2)/ZnO sample might possess more surface reaction sites and adsorb and transport more dye molecules due to the higher BET surface area and many pore channels, also leading to higher photocatalytic activity.

Copper catalysts supported on magnesia promoted ceria are synthesized and used for NO reduction by CO. The supports and the subsequent Cu catalysts are prepared by citric acid sol–gel and impregnation methods, respectively. The results of N2-physisorption, XRD, EPR and TPR measurements indicate that the Mg addition promotes not only the dispersion of CuO, but also the formation of Cu–O–Ce solid solution. The highest amount of Cu–O–Ce solid solution is found in catalyst modified with 5 wt.% MgO. Based on the catalytic performance, two active sites for the reduction NO by CO are proposed: copper matrix and Cu–O–Ce solid solution. The former does not require the involvement of oxygen vacancy and is more active at low temperature range (T

A high yield of nanostructured CuO bundles with different building blocks is successfully prepared through simple hydrothermal and thermal treatment methods. The microstructure of the as-synthesized samples is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 physisorption, and IR spectra. The results show that the microstructure of the CuO bundles, such as different grain sizes, BET surface areas, pore sizes, defects and morphologies of building blocks can be obtained by different synthetic methods. Moreover, H2-TPR and in situ XRD experiments are used to investigate the reduction properties of the nanostructured CuO bundles. It is found that there are two different reduction pathways involved in the reduction processes at 30 mL/min of 10 vol. % H2/N2: for the sample synthesized through the hydrothermal method (CuO-HT), all of the CuO is reduced directly to metallic Cu; however, for the sample synthesized through the thermal treatment method (CuO-TT), all of the CuO is ...

Ag/ZnO heterostructure nanocatalysts with Ag content of 1 wt % are successfully prepared through three different simple methods, where chemical reduction and photolysis reaction are adopted to fabricate the heterostructure. The dispersity of Ag clusters and/or nanoparticles in Ag/ZnO nanocatalyst is investigated by EDX mapping and XPS techniques. The experimental results show that deposition-precipitation is an efficient method to synthesize Ag/ZnO nanocatalyst with highly dispersed Ag clusters and/or nanoparticles; the photocatalytic activity of Ag/ZnO photocatalysts mainly depends on the dispersity of metallic Ag in Ag/ZnO nanocatalyst; the higher the dispersity of metallic Ag in Ag/ZnO nanocatalyst is, the higher the photocatalytic activity of Ag/ZnO photocatalyst should be. In addition, it is also found that the dispersity of Ag/ZnO photocatalyst in the dye solution is another key factor for liquid-phase photocatalysis due to the UV-light utilizing efficiency. The higher the UV-light utilizing efficiency is, the higher the photocatalytic activity of Ag/ZnO heterostructure photocatalyst should be.

A series of Au/Fe 2 O 3 catalysts for the water gas shift (WGS) reaction were prepared by modified deposition-precipitation method. The sample calcined at 300 °C showed higher catalytic activity and better stability than other samples. Using N 2 physisorption, in situ XRD, H 2 -TPR, and XPS techniques, the influence of calcination temperature on properties of Au/Fe 2 O 3 catalyst was explored, and the cause of deactivation was analyzed as well. The results showed that the catalytic behaviors were related to the interaction between Au and Fe 2 O 3 , and the reductive property of support, both of which were significantly affected by calcination temperature. Furthermore, according to the results of XPS, although stable carbonate and carbonyl surface species were found on the spent catalysts, the semiquantitative analysis of these species indicated that they were not the main cause of the deactivation. In fact, the deactivation of Au/Fe 2 O 3 was sensitive to the structure change of support. During the water gas shift reaction, Fe 3 O 4 particle would aggregate and crystallize leading to increase in the crystallinity of support and a significant reduction in the surface area of the catalysts, which resulted in the deactivation of Au/Fe 2 O 3 .

The Au/Fe 2 O 3 catalyst was prepared by co-precipitation, deposition-precipitation, and modified deposition-precipitation methods and was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The catalyst activity for the water-gas shift (WGS) reaction was discussed. Under strictly controlled conditions, the Au/Fe 2 O 3 catalyst prepared by modified deposition-precipitation displayed higher activity for the WGS reaction than that prepared by co-precipitation and deposition-precipitation. In the former case, the CO conversion of 82.3% was obtained with a feed gas of 10% CO/N 2 at 150 °C. Wherein, gold particles of 3–5 nm were highly dispersed on the surface of the Fe 2 O 3 support that existed in an amorphous and crystalline state. A relatively strong interaction between gold particles and the support occurred, which was beneficial for the WGS reaction.