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Non-precious metal catalysts with enhanced low-temperature activity and improved water resistance are highly demanded for emission control. CuO-based catalysts are promising alternatives to precious metal catalysts due to their acceptable activity and cost-effectiveness. However, there is an urgent need to further enhance their low-temperature activity and water resistance for industrial applications. Herein, CuO catalysts supported by various SiO2-TiO2 supports were prepared and evaluated for CO oxidation and NO reduction by CO reactions under the testing conditions with and without water. Among the studied catalysts with different SiO2 contents, CuO/5SiO2-TiO2, in which CuO was supported by SiO2-TiO2 with 5 wt.% SiO2, exhibited the best performance for CO oxidation. Compared with CuO/TiO2 and CuO/SiO2 reference catalysts, the CuO/5SiO2-TiO2 catalyst showed enhanced catalytic activity in both CO oxidation and NO reduction by CO under dry and wet conditions. Comprehensive characterizations revealed that the presence of SiO2 in TiO2 support facilitated the CuO/5SiO2-TiO2 catalyst with a high dispersion and reduced oxidation states of CuOx species. This not only improved the low-temperature reducibility but also enhanced the adsorption of reactive CO species. As a result, the CuO/5SiO2-TiO2 catalyst demonstrated superior catalytic activity. Furthermore, the inclusion of SiO2 in the catalyst inhibited H2O adsorption, contributing to the enhanced water resistance on CuO/5SiO2-TiO2 catalyst. These advantages in catalytic activity and water resistance make CuO/5SiO2-TiO2 a promising candidate for applications in emission control. [ABSTRACT FROM AUTHOR]

Non-precious metal catalysts with enhanced low-temperature activity and improved water resistance are highly demanded for emission control. CuO-based catalysts are promising alternatives to precious metal catalysts due to their acceptable activity and cost-effectiveness. However, there is an urgent need to further enhance their low-temperature activity and water resistance for industrial applications. Herein, CuO catalysts supported by various SiO2-TiO2 supports were prepared and evaluated for CO oxidation and NO reduction by CO reactions under the testing conditions with and without water. Among the studied catalysts with different SiO2 contents, CuO/5SiO2-TiO2, in which CuO was supported by SiO2-TiO2 with 5 wt.% SiO2, exhibited the best performance for CO oxidation. Compared with CuO/TiO2 and CuO/SiO2 reference catalysts, the CuO/5SiO2-TiO2 catalyst showed enhanced catalytic activity in both CO oxidation and NO reduction by CO under dry and wet conditions. Comprehensive characterizations revealed that the presence of SiO2 in TiO2 support facilitated the CuO/5SiO2-TiO2 catalyst with a high dispersion and reduced oxidation states of CuOx species. This not only improved the low-temperature reducibility but also enhanced the adsorption of reactive CO species. As a result, the CuO/5SiO2-TiO2 catalyst demonstrated superior catalytic activity. Furthermore, the inclusion of SiO2 in the catalyst inhibited H2O adsorption, contributing to the enhanced water resistance on CuO/5SiO2-TiO2 catalyst. These advantages in catalytic activity and water resistance make CuO/5SiO2-TiO2 a promising candidate for applications in emission control. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru/MgO catalysts with varied Ru structures are designed for CO 2 hydrogenation. • CO 2 hydrogenation on Ru single-atoms supported by MgO follows the reverse water–gas shift reaction pathway to produce CO. • Ru few-atom cluster sites on MgO are beneficial for H 2 dissociation. • A mixed Ru structure comprising both Ru single-atom and few-atom cluster sites facilitates the CO production. The development and comprehension of supported metal catalysts for CO 2 hydrogenation is of paramount importance in mitigating the net CO 2 emissions. Supported Ru catalysts have been widely recognized in facilitating CO 2 methanation, on which recent findings suggest that the CO 2 hydrogenation process can be manipulated to favor the reverse water–gas shift (RWGS) pathway by precisely adjusting the size of Ru particles. However, the size-dependent impact of Ru remains a topic of lively debate. In this work, Ru/MgO catalysts with Ru in the form of single atoms (Ru 1) and few-atom cluster (Ru FAC) structures were prepared for CO 2 hydrogenation. The 1.0Ru/MgO catalyst (with 1 wt.% of Ru), featuring a mixture of Ru 1 and Ru FAC with a size of 0.6–1.0 nm, showed the highest CO yield (38% at 500 °C) with balanced CO 2 conversion and CO selectivity. Transient CO 2 hydrogenation and temperature-programmed surface reaction (TPSR) studies suggested that the adsorbed CO 2 species participated in CO 2 hydrogenation. On Ru 1 sites, CO 2 hydrogenation followed the RWGS pathway, resulting in the production of CO. In contrast, on Ru FAC sites, the enhanced H 2 dissociation ability, along with the presence of adsorbed bidentate and monodentate carbonate species at the Ru−MgO interfaces, facilitated the formation of CH 4 through the CO 2 methanation pathway. This study highlights the critical roles of Ru structure and local environment in defining the CO 2 hydrogenation pathways and provides new design principles for highly active Ru-based catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Small and uniform CeO 2 nanoparticles were prepared on Al 2 O 3 (CA-T) using a two-step incipient wetness impregnation method. • Pt single sites anchored to step sites of small CeO 2 entities within CA-T were more stable than those anchored to crystal surface of large CeO 2 particles on regular ceria-alumina. • The reactivity of CO adsorbed on Pt sites decreased by Pt cluster step sites ≈ Pt cluster terrace sites > Pt cluster corner sites ≫ Pt single sites on CeO 2. • Abundant Pt cluster step and terrace sites as well as rich Pt-CeO 2 interfaces facilitated the activated Pt/CA-T catalyst for efficient CO oxidation at low temperatures. In heterogeneous catalysis, the promotion of low temperature activity and enhancement of thermal stability simultaneously especially for precious metal catalysts is always highly demanded but very challenging. Herein we report a novel Pt catalyst on ceria-alumina (CeO 2 /Al 2 O 3) support (Pt/CA-T) engineered by a two-step ceria deposition strategy, exhibiting superior thermal stability and low-temperature carbon monoxide (CO) oxidation activity after activation. Pt single sites anchored to engineered CeO 2 edge sites are much more stable than that to CeO 2 (111) surface, and such stable single sites can be transformed into highly active Pt clusters for efficient low-temperature CO oxidation. Active site identification indicates that the CO oxidation activity of different Pt sites follows such sequence: Pt cluster step sites ≈ Pt cluster terrace sites > Pt cluster corner sites ≫ Pt single sites on CeO 2. The excellent low temperature activity of activated Pt/CA-T catalyst for CO oxidation is associated with its abundant Pt cluster step and terrace sites as well as rich Pt-CeO 2 interfaces, which facilitate the adsorption of active CO species and superior oxygen activation/transfer ability. The present study provides new insights into the structure–activity relationship of Pt-CeO 2 -Al 2 O 3 catalyst, which can also guide the preparation of other highly robust supported catalysts for important industrial applications. [ABSTRACT FROM AUTHOR]

Three-dimensionally ordered macroporous CeO 2 (3DOM CeO 2 ) and its supported Pd@Co (Co x Pd/3DOM CeO 2 , x (Co/Pd molar ratio) = 2.4–13.6) nanocatalysts were prepared using the polymethyl methacrylate-templating and modified polyvinyl alcohol-protected reduction methods, respectively. The Pd@Co particles displayed a core-shell (core: Pd; shell: Co) structure with an average size of 3.5–4.5 nm and were well dispersed on the surface of 3DOM CeO 2 . The Co x Pd/3DOM CeO 2 samples exhibited high catalytic performance and super stability for methane oxidation, with the Co 3.5 Pd/3DOM CeO 2 sample showing the highest activity ( T 90% = 480 °C at space velocity of 40,000 mL/(g h) and excellent stability in the temperature range 400–800 °C. The apparent activation energies (58–73 kJ/mol) obtained over Co x Pd/3DOM CeO 2 were much lower than those (104–112 kJ/mol) over Co/3DOM CeO 2 and 3DOM CeO 2 for methane oxidation, with the Co 3.5 Pd/3DOM CeO 2 sample possessing the lowest apparent activation energy (58 kJ/mol). It is concluded that the excellent catalytic performance of Co 3.5 Pd/3DOM CeO 2 was associated with its good abilities to adsorb oxygen and methane as well as the unique core-shell structure of CoPd nanoparticles. [ABSTRACT FROM AUTHOR]

Herein we fabricated the supported single-atom silver catalysts using an in situ molten salt method. The Mn 2 O 3 nanowires supported single-atom silver catalyst (i.e., 0.06 wt% Ag/Mn 2 O 3) exhibited excellent catalytic activity for toluene combustion, with the temperatures required for 50 and 90% of toluene conversions being 170 and 205 °C, respectively, at a space velocity of 40,000 mL/(g h). However, the toluene conversion at 205 °C quickly decreased from 90 to 30% within 2.5 h of on-stream reaction. Based on the various characterization results, we found that there were no aggregation of Ag particles, no change in crystal structure of the Mn 2 O 3 nanowire support, and no carbon deposition on the catalyst surface, and the quick deactivation of 0.06 wt% Ag/Mn 2 O 3 was mainly associated with the low oxygen activation ability. The proper CeO 2 addition to the 0.06 wt% Ag/Mn 2 O 3 catalyst was found to not only improve the catalytic activity but also significantly enhance the stability of the catalyst. Toluene conversion at 195 °C over 0.63 wt% CeO 2 -0.06 wt% Ag/Mn 2 O 3 decreased by only 10% in 50 h of on-stream reaction. Because Ag and CeO 2 particles were highly dispersed on the Mn 2 O 3 nanowire support, the oxygen species formed at the surface oxygen vacancies of CeO 2 could efficiently migrate to the active sites (i.e., the interface of Ag-Mn 2 O 3) and replenish the surface reactive lattice oxygen species. Thus, the present single-atom silver catalyst is an alternative for commercial noble metal catalysts for the removal of VOCs. An in situ molten salt strategy is developed for the convenient preparation of Mn 2 O 3 nanowires-supported single-atom silver catalysts with high activity for toluene oxidation. The significant enhancement in catalytic stability of the ceria-modified single-atom silver catalyst is due to the timely replenishment of the surface reactive lattice oxygen species. Unlabelled Image • Single-atom Ag catalyst is prepared using an in situ molten salt method. • Single-atom Ag catalyst exhibits high catalytic activity for toluene removal. • Ce-doping greatly enhances catalytic stability of single-atom Ag catalyst. • Timely replenishment of surface reactive lattice oxygen species is important. • Single-atom Ag catalyst is an alternative for commercial noble metal catalysts. [ABSTRACT FROM AUTHOR]

Supported 0.05 wt% Pt catalysts, prepared via an in situ molten salt method, show high catalytic activity for acetone removal. Ce-, V-, or W-doping increases the amount of surface acid sites, and then enhances H 2 O-, CO 2 -, and SO 2 -tolerance of 0.05 wt% Pt/TiO 2. The present Pt catalysts might be suitable for oxygenated VOCs removal. • Supported 0.05 wt% Pt catalysts are prepared using an in situ molten salt method. • Supported 0.05 wt% Pt catalysts show high catalytic activity for acetone removal. • Ce-, V-, or W-doping enhance H 2 O-, CO 2 -, and SO 2 -tolerance of 0.05 wt% Pt/TiO 2. • Surface acidity greatly influences SO 2 tolerance of supported 0.05 wt% Pt catalyst. • The present Pt catalysts might be suitable for oxygenated VOCs removal. Volatile organic compounds (VOCs) cause damage to atmospheric environment and human health. Supported noble metal catalysts are widely used to control VOCs emissions. The high cost, and low H 2 O-, CO 2 -, and SO 2 -resistance of such catalysts are worthy to be improved. Herein we fabricated Ce-, V-, or W-doped TiO 2 supported ultralow loading Pt catalysts via the in-situ molten salt method, and evaluated their catalytic performance for acetone (major pollutants in pharmaceutical industry) removal. Under the present reaction conditions, all the catalysts exhibited high catalytic activity and stability for acetone oxidation, with the temperature required 90% acetone conversion being of 245 °C over 0.57 wt% CeO 2 -0.05 wt% Pt/TiO 2. The doping of Ce, V, or W enhanced the H 2 O-, CO 2 -, and SO 2 -tolerance ability of 0.05 wt% Pt/TiO 2. More than 85 %85%, 70%, or 60% of acetone could be removed even in the presence of 20 vol% water vapor, 10 vol% CO 2 , or 100 ppm SO 2 , respectively. The improvement in SO 2 -tolerance ability was due to the inhibition of SO 2 adsorption and oxidation activity as well as Ti(SO 4) 2 or TiOSO 4 formation. Acetone complete oxidation over 0.57 wt% CeO 2 -0.05 wt% Pt/TiO 2 would follow the pathway: adsorbed acetone molecules → acetic acid and formic acid → carbonate species → CO 2 and H 2 O. The present supported Pt catalysts might be suitable for oxygenated VOCs removal. [ABSTRACT FROM AUTHOR]

Three-dimensionally ordered macro-/mesoporous silica (3DOM SiO 2 )-supported manganese oxide and gold nanocatalysts ( y Au/ z MnO x /3DOM SiO 2 , y = 0–0.95 wt%; z = 2.7–15.4 wt% (weight percentage of Mn 2 O 3 )) were prepared using the polymethyl methacrylate-templating, incipient wetness impregnation, and polyvinyl alcohol-protected reduction methods, respectively. It is shown that the y Au/ z MnO x /3DOM SiO 2 samples displayed a high-quality 3DOM architecture with macropores (180–200 nm in diameter) and mesopores (4–6 nm in diameter) and a surface area of 220–318 m 2 /g. MnO x nanoparticles (NPs) with a size of 18.7–25.7 nm were dispersed on the surface of 3DOM SiO 2 , and Au NPs with a size of 3.6–3.8 nm were uniformly dispersed on the surface of z MnO x /3DOM SiO 2 . The 0.93Au/11.2MnO x /3DOM SiO 2 sample performed the best (the temperature required for achieving a 90% toluene conversion was 255 °C at space velocity = 20,000 mL/(g h)) for toluene oxidation. It is concluded that the higher oxygen adspecies concentration, better low-temperature reducibility, and stronger interaction between Au and MnO x NPs as well as the unique bimodal porous structure were responsible for the good catalytic performance of 0.93Au/11.2MnO x /3DOM SiO 2 . [ABSTRACT FROM AUTHOR]

An in situ molten salt strategy is developed for the convenient preparation of iron oxide-supported platinum catalysts with high performance for o -xylene elimination. The high catalytic performance of the supported platinum catalysts is due to the improvement in redox ability and o -xylene activation. • Supported Pt catalyst is prepared using an in situ molten salt method. • Supported Pt catalyst exhibits high catalytic activity for o -xylene removal. • Pt loading enhances the redox ability of the supported Pt catalyst. • Pt loading improves the adsorption and activation of o -xylene. • Improvement in redox ability and o -xylene activation benefit high activity. Supported noble metal catalysts are highly effective for eliminating volatile organic compounds (VOCs). A catalyst with less noble metal loading is always desirable. Using a mixture of NaNO 3 and NaF as molten salt, Fe(NO 3) 3 and Pt(NH 3) 4 (NO 3) 2 as metal precursors, x Pt/Fe 2 O 3 catalysts (x = 0–0.3 wt%) were fabricated after calcination at 350 °C for 3 h. At space velocity of 40,000 mL/(g h), 0.22 wt% Pt/Fe 2 O 3 showed the best catalytic activity, and o -xylene could be completely oxidized into CO 2 and H 2 O at 225 °C. Furthermore, 0.22 wt% Pt/Fe 2 O 3 exhibited good stability, and high resistance to water vapor, CO 2 , and SO 2. We deduce that the excellent catalytic performance of 0.22 wt% Pt/Fe 2 O 3 was associated with the high dispersion of the Pt species and good low-temperature reducibility. The possible reaction mechanism of o -xylene oxidation over 0.22 wt% Pt/Fe 2 O 3 involved the adsorption of o -xylene molecules, partial decomposition into small organic intermediates (e.g. maleic anhydride and aliphatic carboxylate species), and total oxidation into CO 2 and H 2 O. Due to the high efficiency, good stability, low cost, and convenient preparation, the present catalysts are promising for the practical removal of VOCs. [ABSTRACT FROM AUTHOR]

Three-dimensionally ordered macro-/mesoporous 26.9 wt% CeO 2 –Al 2 O 3 (denoted as 3DOM 26.9CeO 2 –Al 2 O 3 )-supported noble metal nanocatalysts ( x M/3DOM 26.9CeO 2 –Al 2 O 3 , x = 0.27–0.81 wt%; M = Au, Ag, Pd, and Pt) were prepared using the polymethyl methacrylate-templating and polyvinyl pyrrolidone- or polyvinyl alcohol-protected reduction methods, respectively. It is shown that the x M/3DOM 26.9CeO 2 –Al 2 O 3 samples displayed a high-quality 3DOM architecture with a bimodal pore (macropore size = 180–200 nm and mesopore size = 4–6 nm) structure and a surface area of 102–108 m 2 /g, with the noble metal nanoparticles (3–4 nm in size) being highly dispersed on the 3DOM 26.9CeO 2 –Al 2 O 3 surface. The 0.27Pt/3DOM 26.9CeO 2 –Al 2 O 3 sample performed the best ( T 90% = 198 °C at space velocity = 20,000 mL/(g h)) for toluene oxidation. The addition of moisture to the feedstock induced a positive effect on catalytic activity. The apparent activation energies obtained over the x M/3DOM 26.9CeO 2 –Al 2 O 3 samples were in the range of 46–100 kJ/mol, with the 0.27Pt/3DOM 26.9CeO 2 –Al 2 O 3 sample possessing the lowest apparent activation energy. It is concluded that the good catalytic performance of 0.27Pt/3DOM 26.9CeO 2 –Al 2 O 3 was associated with its higher adsorbed oxygen species concentration, better low-temperature reducibility, and stronger interaction between Pt and 3DOM 26.9CeO 2 –Al 2 O 3 as well as the unique bimodal porous structure. [ABSTRACT FROM AUTHOR]

Abstract: Porous LaFeO3 (LFO) samples with surface areas of 15–26m2/g and orthorhombic structures were prepared via a glucose-assisted hydrothermal route. Physicochemical properties of the materials were characterized by means of a number of techniques, and their catalytic activities were evaluated for toluene combustion. It is found that the sample (LFO-170) derived at a hydrothermal temperature of 170°C possessed the highest surface area and surface oxygen concentration and the best low-temperature reducibility. Among the LFO samples, the LFO-170 sample showed the best performance for toluene combustion, giving the T 10%, T 50%, and T 90% of 180, 250, and 270°C at space velocity=20,000mL/(gh), respectively. The apparent activation energies of the LFO samples were 50–55kJ/mol. We believe that the high surface area and surface oxygen concentration and good low-temperature reducibility were responsible for the good catalytic performance of the LFO-170 sample. [Copyright &y& Elsevier]

Understanding the nature of active sites on metal oxide catalysts in the selective catalytic reduction (SCR) of NO by NH 3 (NH 3 -SCR) is a crucial prerequisite for the development of novel efficient NH 3 -SCR catalysts. In this work, two CeO 2 -based SCR catalyst systems with diverse acidic metal oxides-CeO 2 interfaces, i.e., Nb 2 O 5 -CeO 2 (Nb 2 O 5 /CeO 2 and CeO 2 /Nb 2 O 5) and WO 3 -CeO 2 (WO 3 /CeO 2 and CeO 2 /WO 3), were prepared and used to reveal the relationship between NH 3 -SCR activity and surface acidity/redox properties. In combination with the results of the NH 3 -SCR activity test and various characterizations, it was found that the NH 3 -SCR performance of Nb 2 O 5 -CeO 2 and WO 3 -CeO 2 catalysts was highly dependent on the strong interactions between the redox component (CeO 2) and acidic component (Nb 2 O 5 or WO 3), as well as the amount of paired redox-acid sites. From a quantitative perspective, an activity-surface acidity/redox property relationship was proposed. For both Nb 2 O 5 -CeO 2 and WO 3 -CeO 2 catalysts systems operated at the more concerned low-temperature range (200 °C), the NH 3 -SCR activity in low NO x conversion region (< 40%) was mainly dominated by the surface acidity of catalysts, while the NH 3 -SCR activity in high NO x conversion region (> 40%) was more determined by redox properties. [Display omitted] • Nb 2 O 5 -CeO 2 and WO 3 -CeO 2 catalysts with tuned redox-acid property were synthesized. • Paired redox-acid sites formed through strong interaction between Nb 2 O 5 /WO 3 and CeO 2. • NH 3 -SCR activity was well controlled by the paired redox-acid sites. • Surface acidity and redox property were investigated from a quantitative perspective. • A clear surface acidity/redox property-activity relationship was established. [ABSTRACT FROM AUTHOR]