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2019 Volume 40 Issue 12
2019, 40(12):
Abstract:
Preface to the Special Issue of the 17th Chinese National Youth Conference on Catalysis (17th CNYCC)
2019, 40(12): 1821-1821
doi: S1872-2067(19)63491-1
Abstract:
2019, 40(12): 1822-1840
doi: S1872-2067(19)63284-5
Abstract:
Oxygen evolution reactions (OERs) as core components of energy conversion and storage technology systems, such as water splitting and rechargeable metal-air batteries, have attracted considerable attention in recent years. Transition metal compounds, particularly layered double hydroxides (LDHs), are considered as the most promising electrocatalysts owing to their unique two-dimensional layer structures and tunable components. However, heir poor intrinsic electrical conductivities and the limited number of active sites hinder their performances. The regulation of the electronic structure is an effective approach to improve the OER activity of LDHs, including cationic and anionic regulation, defect engineering, regulation of intercalated anions, and surface modifications. In this review, we summarize recent advances in the regulation of the electronic structures of LDHs used as electrocatalysts in OERs. In addition, we discuss the effects of each regulation type on OER activities. This review is expected to shed light on the development and design of effective OER electrocatalysts by summarizing various electronic structure regulation pathways and the effects on their catalytic performances.
Oxygen evolution reactions (OERs) as core components of energy conversion and storage technology systems, such as water splitting and rechargeable metal-air batteries, have attracted considerable attention in recent years. Transition metal compounds, particularly layered double hydroxides (LDHs), are considered as the most promising electrocatalysts owing to their unique two-dimensional layer structures and tunable components. However, heir poor intrinsic electrical conductivities and the limited number of active sites hinder their performances. The regulation of the electronic structure is an effective approach to improve the OER activity of LDHs, including cationic and anionic regulation, defect engineering, regulation of intercalated anions, and surface modifications. In this review, we summarize recent advances in the regulation of the electronic structures of LDHs used as electrocatalysts in OERs. In addition, we discuss the effects of each regulation type on OER activities. This review is expected to shed light on the development and design of effective OER electrocatalysts by summarizing various electronic structure regulation pathways and the effects on their catalytic performances.
2019, 40(12): 1841-1846
doi: S1872-2067(19)63379-6
Abstract:
An efficient C-P bond formation reaction was developed by virtue of the synergetic catalysis strategy by merging heterogeneous photocatalysis and nickel catalysis. This platform utilizing cadmium sulfide semiconductors as heterogeneous photocatalysts and nickel complexes as transition metal catalysts provided a variety of organophosphorus compounds from readily available aryl and vinyl halides, as well as aryl triflates, with generally a good-to-excellent reaction efficiency (31 examples, 46%-98% yields). The current protocol features mild reaction conditions, a broad substrate scope, recyclability of photocatalysts, and inexpensive catalysts, thus defining the practical and economic proprieties of the present catalyst system.
An efficient C-P bond formation reaction was developed by virtue of the synergetic catalysis strategy by merging heterogeneous photocatalysis and nickel catalysis. This platform utilizing cadmium sulfide semiconductors as heterogeneous photocatalysts and nickel complexes as transition metal catalysts provided a variety of organophosphorus compounds from readily available aryl and vinyl halides, as well as aryl triflates, with generally a good-to-excellent reaction efficiency (31 examples, 46%-98% yields). The current protocol features mild reaction conditions, a broad substrate scope, recyclability of photocatalysts, and inexpensive catalysts, thus defining the practical and economic proprieties of the present catalyst system.
2019, 40(12): 1847-1853
doi: S1872-2067(19)63411-X
Abstract:
CO oxidation is of great importance in both fundamental study and industrial application. Supported noble metal catalysts are highly active for CO oxidation but suffer from the scarcity and high cost. Single-atom catalysts (SACs) can maximize the metal atom efficiency. Herein, ZnO nanowire (ZnO-nw) supported Rh, Au, and Pt SACs were successfully developed to investigate their CO oxidation performance. Interestingly, it was found that Rh1/ZnO-nw showed much higher activity than the other noble metals which are usually regarded as good candidates for CO oxidation. In addition, the Rh SAC possessed high stability in high-temperature CO oxidation under simulated conditions in the presence of water and hydrocarbons. The high activity and stability make Rh1/ZnO-nw promising for practical applications, especially in the automotive exhaust emission control. Theoretical calculations indicate that the CO oxidation proceeds via the Mars-van Krevelen mechanism and the lowest barrier for the rate-limiting O2 dissociation at a surface oxygen vacancy site is a key factor in determining the observed highest activity of Rh1/ZnO-nw amongst the studied SACs.
CO oxidation is of great importance in both fundamental study and industrial application. Supported noble metal catalysts are highly active for CO oxidation but suffer from the scarcity and high cost. Single-atom catalysts (SACs) can maximize the metal atom efficiency. Herein, ZnO nanowire (ZnO-nw) supported Rh, Au, and Pt SACs were successfully developed to investigate their CO oxidation performance. Interestingly, it was found that Rh1/ZnO-nw showed much higher activity than the other noble metals which are usually regarded as good candidates for CO oxidation. In addition, the Rh SAC possessed high stability in high-temperature CO oxidation under simulated conditions in the presence of water and hydrocarbons. The high activity and stability make Rh1/ZnO-nw promising for practical applications, especially in the automotive exhaust emission control. Theoretical calculations indicate that the CO oxidation proceeds via the Mars-van Krevelen mechanism and the lowest barrier for the rate-limiting O2 dissociation at a surface oxygen vacancy site is a key factor in determining the observed highest activity of Rh1/ZnO-nw amongst the studied SACs.
2019, 40(12): 1854-1859
doi: S1872-2067(19)63287-0
Abstract:
As a powerful and sensitive tool for the characterization of zeolite building units, UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites. The results show that the behavior of double 6-membered rings (D6Rs) in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation. For the transformation of FAU to CHA, because both zeolites contain the same D6R units, direct transformation occurs, in which the D6Rs were largely unchanged. In contrast, for the transformation of FAU to MFI, the D6Rs can be divided into two single 6-membered rings (S6Rs), which further assembled into the MFI structure. In this crystallization, 5-membered rings (5Rs) are only observed in the MFI framework formation, suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs. These insights will be helpful for further understanding of the interzeolite transformation.
As a powerful and sensitive tool for the characterization of zeolite building units, UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites. The results show that the behavior of double 6-membered rings (D6Rs) in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation. For the transformation of FAU to CHA, because both zeolites contain the same D6R units, direct transformation occurs, in which the D6Rs were largely unchanged. In contrast, for the transformation of FAU to MFI, the D6Rs can be divided into two single 6-membered rings (S6Rs), which further assembled into the MFI structure. In this crystallization, 5-membered rings (5Rs) are only observed in the MFI framework formation, suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs. These insights will be helpful for further understanding of the interzeolite transformation.
2019, 40(12): 1860-1866
doi: S1872-2067(19)63306-1
Abstract:
Controlling the morphology and size of materials is very important for their chemical and physical properties. Herein, we synthesized a novel hexagonal annular Mn(OH)F by a simple hydrothermal method. We also investigated the growth process of the materials from hexagonal block to hexagonal ring via controlling the hydrothermal temperature and time. Comparing with the hexagonal block, the hexagonal rings showed enhanced electrocatalytic water oxidation performance in alkaline solutions. The observed catalytic performance of this novel Mn(OH)F is correlated to its unique structure. Furthermore, we expect that Mn(OH)F would be a new type of Mn-based water oxidation catalyst.
Controlling the morphology and size of materials is very important for their chemical and physical properties. Herein, we synthesized a novel hexagonal annular Mn(OH)F by a simple hydrothermal method. We also investigated the growth process of the materials from hexagonal block to hexagonal ring via controlling the hydrothermal temperature and time. Comparing with the hexagonal block, the hexagonal rings showed enhanced electrocatalytic water oxidation performance in alkaline solutions. The observed catalytic performance of this novel Mn(OH)F is correlated to its unique structure. Furthermore, we expect that Mn(OH)F would be a new type of Mn-based water oxidation catalyst.
2019, 40(12): 1867-1873
doi: S1872-2067(19)63331-0
Abstract:
The search for active, stable, and cost-effective electrocatalysts for hydrogen evolution reaction (HER) is desirable, but it remains a great challenge in the overall water splitting. Here, we report the synthesis of nickel boron nanoparticles supported on Vulcan carbon (Ni-B) via a simple, yet scalable, two-step chemical reduction-annealing strategy. The results of the electrochemical measurements suggest that the overpotentials of Ni-B-400 are 114 and 215 mV (in 1 mol L-1 KOH) at current densities of 10 and 40 mA cm-2, respectively, indicating an exceedingly good electrocatalytic activity in the HER. More importantly, Ni-B maintains a current density of 7.6 mA cm-2 at an overpotential of 0.15 V for 20 h in the durability test. The excellent HER activity of Ni-B-400 is derived from the small particle size and the expanded lattice of Ni, which can optimize the hydrogen absorption energy and enhance the electrocatalytic properties.
The search for active, stable, and cost-effective electrocatalysts for hydrogen evolution reaction (HER) is desirable, but it remains a great challenge in the overall water splitting. Here, we report the synthesis of nickel boron nanoparticles supported on Vulcan carbon (Ni-B) via a simple, yet scalable, two-step chemical reduction-annealing strategy. The results of the electrochemical measurements suggest that the overpotentials of Ni-B-400 are 114 and 215 mV (in 1 mol L-1 KOH) at current densities of 10 and 40 mA cm-2, respectively, indicating an exceedingly good electrocatalytic activity in the HER. More importantly, Ni-B maintains a current density of 7.6 mA cm-2 at an overpotential of 0.15 V for 20 h in the durability test. The excellent HER activity of Ni-B-400 is derived from the small particle size and the expanded lattice of Ni, which can optimize the hydrogen absorption energy and enhance the electrocatalytic properties.
2019, 40(12): 1874-1883
doi: S1872-2067(19)63340-1
Abstract:
A rational integration of multiple reactive centers into a combined unit to facilitate their cooperative effects is a smart approach for accelerating the catalytic activity. Here, to achieve this goal, linear imidazolium-based ionic polymers were confined into the nanopores of mesoporous silica nanospheres anchored with homogeneously distributed zinc salts. Owing to the flexible character and the reinforced cooperative effects of the ionic liquid (nucleophile) and zinc species (Lewis acid) in the confined mesoporous structure, the resultant composite exhibited dramatically improved catalytic performance in the cycloaddition of CO2 with epoxides to form cyclic carbonates. This was in contrast to that observed for the individual catalytic components. Moreover, such a solid catalyst could be easily recovered and reused four times without a significant loss of activity.
A rational integration of multiple reactive centers into a combined unit to facilitate their cooperative effects is a smart approach for accelerating the catalytic activity. Here, to achieve this goal, linear imidazolium-based ionic polymers were confined into the nanopores of mesoporous silica nanospheres anchored with homogeneously distributed zinc salts. Owing to the flexible character and the reinforced cooperative effects of the ionic liquid (nucleophile) and zinc species (Lewis acid) in the confined mesoporous structure, the resultant composite exhibited dramatically improved catalytic performance in the cycloaddition of CO2 with epoxides to form cyclic carbonates. This was in contrast to that observed for the individual catalytic components. Moreover, such a solid catalyst could be easily recovered and reused four times without a significant loss of activity.
Tailoring the surface structures of iron oxide nanorods to support Au nanoparticles for CO oxidation
2019, 40(12): 1884-1894
doi: S1872-2067(19)63374-7
Abstract:
Iron oxide supported Au nanomaterials are one of the most studied catalysts for low-temperature CO oxidation. Catalytic performance not only critically depends on the size of the supported Au nanoparticles (NPs) but also strongly on the chemical nature of the iron oxide. In this study, Au NPs supported on iron oxide nanorods with different surface properties through β-FeOOH annealing, at varying temperatures, were synthesized, and applied in the CO oxidation. Detailed characterizations of the interactions between Au NPs and iron oxides were obtained by X-ray diffraction, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The results indicate that the surface hydroxyl group on the Au/FeOOH catalyst, before calcination (Au/FeOOH-fresh), could facilitate the oxygen adsorption and dissociation on positively charged Au, thereby contributing to the low-temperature CO oxidation reactivity. After calcination at 200℃, under air exposure, the chemical state of the supported Au NP on varied iron oxides partly changed from metal cation to Au0, along with the disappearance of the surface OH species. Au/FeOOH with the highest Au0 content exhibits the highest activity in CO oxidation, among the as-synthesized catalysts. Furthermore, good durability in CO oxidation was achieved over the Au/FeOOH catalyst for 12 h without observable deactivation. In addition, the advanced identical-location TEM method was applied to the gas phase reaction to probe the structure evolution of the Au/iron oxide series of the catalysts and support structure. A Au NP size-dependent Ostwald ripening process mediated by the transport of Au(CO)x mobile species under certain reaction conditions is proposed, which offers a new insight into the validity of the structure-performance relationship.
Iron oxide supported Au nanomaterials are one of the most studied catalysts for low-temperature CO oxidation. Catalytic performance not only critically depends on the size of the supported Au nanoparticles (NPs) but also strongly on the chemical nature of the iron oxide. In this study, Au NPs supported on iron oxide nanorods with different surface properties through β-FeOOH annealing, at varying temperatures, were synthesized, and applied in the CO oxidation. Detailed characterizations of the interactions between Au NPs and iron oxides were obtained by X-ray diffraction, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The results indicate that the surface hydroxyl group on the Au/FeOOH catalyst, before calcination (Au/FeOOH-fresh), could facilitate the oxygen adsorption and dissociation on positively charged Au, thereby contributing to the low-temperature CO oxidation reactivity. After calcination at 200℃, under air exposure, the chemical state of the supported Au NP on varied iron oxides partly changed from metal cation to Au0, along with the disappearance of the surface OH species. Au/FeOOH with the highest Au0 content exhibits the highest activity in CO oxidation, among the as-synthesized catalysts. Furthermore, good durability in CO oxidation was achieved over the Au/FeOOH catalyst for 12 h without observable deactivation. In addition, the advanced identical-location TEM method was applied to the gas phase reaction to probe the structure evolution of the Au/iron oxide series of the catalysts and support structure. A Au NP size-dependent Ostwald ripening process mediated by the transport of Au(CO)x mobile species under certain reaction conditions is proposed, which offers a new insight into the validity of the structure-performance relationship.
2019, 40(12): 1895-1903
doi: S1872-2067(19)63338-3
Abstract:
Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction (ORR) for the application in low temperature fuel cells and beyond, thus their facile and green synthesis is highly demanded. Herein we initially report an alternate aqueous phase one-pot synthesis of such catalysts (containing nominally ca. 20 wt.% Pt) based on dimethylamine borane (DMAB) reduction. The as-obtained electrocatalyst (denoted as Pt3Co/C-DMAB) is compared with the ones obtained by NaBH4 and N2H4·H2O reduction (denoted as Pt3Co/C-NaBH4 and Pt3Co/C-N2H4·H2O, respectively) as well as a commercial Pt/C, in terms of the structure and electrocatalytic property. It turns out that Pt3Co/C-DMAB exhibits the highest ORR performance among all the tested samples in an O2-saturated 0.1 mol/L HClO4, with the mass activity (specific activity) ca. 4 (6) times as large as that for Pt/C. After 10000 cycles of the accelerated degradation test, the half-wave potential for ORR on Pt3Co/C-DMAB decreases only by 4 mV, in contrast to 24 mV for that on Pt/C. Pt3Co/C-NaBH4 or Pt3Co/C-N2H4·H2O shows a specific activity comparable to that for Pt3Co/C-DMAB, but a mass activity similar to that for Pt/C. ICP-AES, TEM, XRD and XPS characterizations indicate that Pt3Co nanoparticles are well-dispersed and alloyed with a mean particle size of ca. 3.4 ±0.4 nm, contributing to the prominent electrocatalytic performance of Pt3Co/C-DMAB. This simple aqueous synthetic route may provide an alternate opportunity for developing efficient practical electrocatalysts for ORR.
Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction (ORR) for the application in low temperature fuel cells and beyond, thus their facile and green synthesis is highly demanded. Herein we initially report an alternate aqueous phase one-pot synthesis of such catalysts (containing nominally ca. 20 wt.% Pt) based on dimethylamine borane (DMAB) reduction. The as-obtained electrocatalyst (denoted as Pt3Co/C-DMAB) is compared with the ones obtained by NaBH4 and N2H4·H2O reduction (denoted as Pt3Co/C-NaBH4 and Pt3Co/C-N2H4·H2O, respectively) as well as a commercial Pt/C, in terms of the structure and electrocatalytic property. It turns out that Pt3Co/C-DMAB exhibits the highest ORR performance among all the tested samples in an O2-saturated 0.1 mol/L HClO4, with the mass activity (specific activity) ca. 4 (6) times as large as that for Pt/C. After 10000 cycles of the accelerated degradation test, the half-wave potential for ORR on Pt3Co/C-DMAB decreases only by 4 mV, in contrast to 24 mV for that on Pt/C. Pt3Co/C-NaBH4 or Pt3Co/C-N2H4·H2O shows a specific activity comparable to that for Pt3Co/C-DMAB, but a mass activity similar to that for Pt/C. ICP-AES, TEM, XRD and XPS characterizations indicate that Pt3Co nanoparticles are well-dispersed and alloyed with a mean particle size of ca. 3.4 ±0.4 nm, contributing to the prominent electrocatalytic performance of Pt3Co/C-DMAB. This simple aqueous synthetic route may provide an alternate opportunity for developing efficient practical electrocatalysts for ORR.
2019, 40(12): 1904-1911
doi: S1872-2067(19)63442-X
Abstract:
Direct ethanol fuel cell is a promising low temperature fuel cell, but its development is hindered by sluggish kinetics of anode catalysts for ethanol oxidation. Here a high efficient platinum/tin oxide/Graphene nanocomposite is synthesized through a facile and environmentally benign method. The structure and morphology are carefully characterized by X-ray diffraction and Transmission electron microscopy, showing a clear platinum/tin oxide heterostructure uniformly dispersed on graphene support. This catalyst demonstrates the highest activity among the reported catalysts and much higher durability towards ethanol oxidation compared to conventional platinum nanocatalysts. The ultrahigh activity originates from promoted removal of poisoning carbon monoxide immediate species on platinum due to a strong electronic donating effect from both tin oxide and graphene, which is fully supported by carbon monoxide stripping and X-ray photoelectron spectroscopy analysis. Our platinum/tin oxide/Graphene appears to be a promising candidate for ethanol oxidation electrocatalysts.
Direct ethanol fuel cell is a promising low temperature fuel cell, but its development is hindered by sluggish kinetics of anode catalysts for ethanol oxidation. Here a high efficient platinum/tin oxide/Graphene nanocomposite is synthesized through a facile and environmentally benign method. The structure and morphology are carefully characterized by X-ray diffraction and Transmission electron microscopy, showing a clear platinum/tin oxide heterostructure uniformly dispersed on graphene support. This catalyst demonstrates the highest activity among the reported catalysts and much higher durability towards ethanol oxidation compared to conventional platinum nanocatalysts. The ultrahigh activity originates from promoted removal of poisoning carbon monoxide immediate species on platinum due to a strong electronic donating effect from both tin oxide and graphene, which is fully supported by carbon monoxide stripping and X-ray photoelectron spectroscopy analysis. Our platinum/tin oxide/Graphene appears to be a promising candidate for ethanol oxidation electrocatalysts.
2019, 40(12): 1912-1923
doi: S1872-2067(19)63433-9
Abstract:
A series of UiO-66-NH2/Ag2CO3 Z-scheme heterojunctions were prepared by a simple ion-exchange-solution method using UiO-66-NH2 and semiconductor Ag2CO3 as precursors. The photocatalytic activities of UAC-X (UAC-20, 50, 100, 150, 200) Z-scheme heterojunctions toward the hexavalent chromium (Cr(VI)) reduction and UAC-100 toward oxidative degradation of four organic dyes like rhodamine B (RhB), methyl orange (MO), congo red (CR), and methylene blue (MB) under visible light irradiation were investigated. The effects of different pH (pH=2, 3, 4, 6, 8), small organic acids (citric acid, tartaric acid, and oxalic acid), and foreign ions (ions in tap water and surface water) on Cr(VI) reduction were explored. The results revealed that the UAC-100 heterojunctions displayed more remarkable Cr(VI) reduction performance than the pristine UiO-66-NH2 and Ag2CO3, resulting from the improved separation of photo-induced electrons and holes. The enhanced photocatalytic activity of UAC-100 was further confirmed by the photoluminescence measurement, electrochemical analysis, and active species trapping experiments. After four cycles' experiments, the photocatalytic Cr(VI) reduction efficiency over UAC-100 was still over 99%, which exhibited that UAC-100 had excellent reusability and stability. Finally, the corresponding photocatalytic reaction mechanism was proposed and tested.
A series of UiO-66-NH2/Ag2CO3 Z-scheme heterojunctions were prepared by a simple ion-exchange-solution method using UiO-66-NH2 and semiconductor Ag2CO3 as precursors. The photocatalytic activities of UAC-X (UAC-20, 50, 100, 150, 200) Z-scheme heterojunctions toward the hexavalent chromium (Cr(VI)) reduction and UAC-100 toward oxidative degradation of four organic dyes like rhodamine B (RhB), methyl orange (MO), congo red (CR), and methylene blue (MB) under visible light irradiation were investigated. The effects of different pH (pH=2, 3, 4, 6, 8), small organic acids (citric acid, tartaric acid, and oxalic acid), and foreign ions (ions in tap water and surface water) on Cr(VI) reduction were explored. The results revealed that the UAC-100 heterojunctions displayed more remarkable Cr(VI) reduction performance than the pristine UiO-66-NH2 and Ag2CO3, resulting from the improved separation of photo-induced electrons and holes. The enhanced photocatalytic activity of UAC-100 was further confirmed by the photoluminescence measurement, electrochemical analysis, and active species trapping experiments. After four cycles' experiments, the photocatalytic Cr(VI) reduction efficiency over UAC-100 was still over 99%, which exhibited that UAC-100 had excellent reusability and stability. Finally, the corresponding photocatalytic reaction mechanism was proposed and tested.
2019, 40(12): 1924-1933
doi: S1872-2067(19)63429-7
Abstract:
The design and preparation of suitable supports are of great importance for gold catalysts to attain excellent catalytic performance for alcohol oxidation. In this work, we found that ZnO-CuO mixed oxides supported gold catalysts showed much better catalytic activity for base-free aerobic oxidation of benzyl alcohol than Au/ZnO and Au/CuO catalysts, and among them Au/Zn0.7Cu0.3O displayed the best catalytic performance. In addition, the Au/Zn0.7Cu0.3O catalyst could selectively catalyze the aerobic oxidation of a wide range of alcohols to produce the corresponding carbonyl compounds with high yields under mild conditions without base. Further characterizations indicated that the outstanding catalytic performance of Au/Zn0.7Cu0.3O was correlated with the small size of Au nanoparticles (NPs), good low-temperature reducibility, high concentration of surface oxygen species, and collaborative interaction between Au NPs and mixed oxide.
The design and preparation of suitable supports are of great importance for gold catalysts to attain excellent catalytic performance for alcohol oxidation. In this work, we found that ZnO-CuO mixed oxides supported gold catalysts showed much better catalytic activity for base-free aerobic oxidation of benzyl alcohol than Au/ZnO and Au/CuO catalysts, and among them Au/Zn0.7Cu0.3O displayed the best catalytic performance. In addition, the Au/Zn0.7Cu0.3O catalyst could selectively catalyze the aerobic oxidation of a wide range of alcohols to produce the corresponding carbonyl compounds with high yields under mild conditions without base. Further characterizations indicated that the outstanding catalytic performance of Au/Zn0.7Cu0.3O was correlated with the small size of Au nanoparticles (NPs), good low-temperature reducibility, high concentration of surface oxygen species, and collaborative interaction between Au NPs and mixed oxide.
