Simultaneously enhancing the reaction kinetics,mass transport,and gas release during alkaline hydrogen evolution reaction(HER)is critical to minimizing the reaction polarization resistance,but remains a big challenge....Simultaneously enhancing the reaction kinetics,mass transport,and gas release during alkaline hydrogen evolution reaction(HER)is critical to minimizing the reaction polarization resistance,but remains a big challenge.Through rational design of a hierarchical multiheterogeneous three-dimensionally(3D)ordered macroporous Mo_(2)C-embedded nitrogen-doped carbon with ultrafine Ru nanoclusters anchored on its surface(OMS Mo_(2)C/NC-Ru),we realize both electronic and morphologic engineering of the catalyst to maximize the electrocatalysis performance.The formed Ru-NC heterostructure shows regulative electronic states and optimized adsorption energy with the intermediate H*,and the Mo_(2)C-NC heterostructure accelerates the Volmer reaction due to the strong water dissociation ability as confirmed by theoretical calculations.Consequently,superior HER activity in alkaline solution with an extremely low overpotential of 15.5 mV at 10 mAcm^(−2)with the mass activity more than 17 times higher than that of the benchmark Pt/C,an ultrasmall Tafel slope of 22.7 mV dec−1,and excellent electrocatalytic durability were achieved,attributing to the enhanced mass transport and favorable gas release process endowed from the unique OMS Mo_(2)C/NC-Ru structure.By oxidizing OMS Mo_(2)C/NC-Ru into OMS MoO_(3)-RuO_(2)catalyst,it can also be applied as efficient oxygen evolution electrocatalyst,enabling the construction of a quasi-symmetric electrolyzer for overall water splitting.Such a device's performance surpassed the state-of-the-art Pt/C||RuO2 electrolyzer.This study provides instructive guidance for designing 3D-ordered macroporous multicomponent catalysts for efficient catalytic applications.展开更多
Aluminum-metal batteries show great potential as next-generation energy storage due to their abundant resources and intrinsic safety.However,the crucial limitations of metallic Al anodes,such as dendrite and corrosion...Aluminum-metal batteries show great potential as next-generation energy storage due to their abundant resources and intrinsic safety.However,the crucial limitations of metallic Al anodes,such as dendrite and corrosion problems in conventional aluminum-metal batteries,remain challenging and elusive.Here,we report a novel electrodeposition strategy to prepare an optimized 3D Al anode on carbon cloth with an uniform deposition morphology,low local current density,and mitigatory volume change.The symmetrical cells with the 3D Al anode show superior stable cycling(>450 h)and low-voltage hysteresis(~170 mV)at 0.5 mA cm^(−2).High reversibility(~99.7%)is achieved for the Al plating/stripping.The graphite||Al‐4/CC full batteries show a long lifespan of 800 cycles with 54 mAh g^(−1) capacity at a high current density of 1000 mA g^(−1),benefiting from the high capacitive-controlled distribution.This study proposes a novel strategy to design 3D Al anodes for metallic-Al-based batteries by eliminating the problems of planar Al anodes and realizing the potential applications of aluminum-graphite batteries.展开更多
CoPS nanoparticles encapsulated with S,P,N tri-doped carbon material(SPNC)were proposed as bifunctional electrocatalyst of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)derived from zeolitic imidazol...CoPS nanoparticles encapsulated with S,P,N tri-doped carbon material(SPNC)were proposed as bifunctional electrocatalyst of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)derived from zeolitic imidazolate framework-67.Density functional theory calculations consistently revealed that P element in CoPS@SPNC improves the electrical conductivity and reduces OH^(*)hydrogenation energy barrier on Co sites,thereby facilitating the overall ORR/OER activities.A flexible Zn–air battery with CoPS@SPNC delivered an overpotential of 0.49 V,an energy efficiency above 80%,and a discharge voltage of 1.29 V at 2 mA cm^(-2) for 80 h.展开更多
Microchannel reactors usually have some microchannels with characteristic sizes(i.e., between 1 and 1000 μm). Small channel size and diversity are usually patterned in a microchannel reactor, and these features incre...Microchannel reactors usually have some microchannels with characteristic sizes(i.e., between 1 and 1000 μm). Small channel size and diversity are usually patterned in a microchannel reactor, and these features increase the surface area-to-volume ratio and driving force for heat and mass transport. Microchannel reactors are widely used in the petrochemistry, aerospace, electronics, information technology, and automotive industries, among others. According to the geometric shape of microchannels, a microchannel reactor can be classified as parallel, curved, micro-pin-fin array, bionic, or 3D network type. This review summarizes the fabrication methods of microchannel reactors, including traditional mechanical processing, chemical etching, electroforming injection molding technology, non-traditional machining, and sintering. It also presents the various applications of microchannel reactors in catalytic reactions, heat transfer, mixing, and other areas. Finally, this review describes the development and application prospects of microchannel reactors.展开更多
Catalytic ozonation is progressively becoming an attractive technique for quick water purification but efficient and stable catalysts remains elusive. Here we solvothermally synthesized highly-dispersed Co3O4 nanocrys...Catalytic ozonation is progressively becoming an attractive technique for quick water purification but efficient and stable catalysts remains elusive. Here we solvothermally synthesized highly-dispersed Co3O4 nanocrystals over microscale nitrogen-doping graphene （NG） nanosheets and tested it as a synthetic catalyst in the ozonation of phenol in aqueous solutions. Transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were used to determine its morphology, crystallinity, elemental composition and molecular bonds, respectively. The comparative experiments confirmed the highest catalytic activity and oxidation degree （AOSC） of Co3O4/NG among four nanocomposites （G, NG, Co3O4/G, and Co3OJNG）. Co3O4/NG also has exhibited the highest degradation rate： complete conversion of a near-saturated concentration of phenol （941.1 mg/L） was achieved within 30 min under ambient conditions with only a small dosage of Co3O4/NG （50 mg/L） and ozone （4 mg/L, flow rate： 0.5 L/min）. It also resulted in 34.6% chemical oxygen demand （CODcr） and 24.2% total organic carbon （TOC） reduction. In this work, graphene nanosheets not only functioned as a support for Co3O4 nanocrystals but also functioned as a co-catalyst for the enhancement in phenol removal efficiency. The surface nitridation and Co3O4 modification treatment further improved the removal rate of the phenol pollutants and brought in the higher oxidation degree. Our finding may open new perspectives for pursuing exceptional activity for catalytic ozonation reaction.展开更多
Basic oxygen furnace steelmaking leads to the production of CO-rich off-gas.When CO and NO are combined in off-gas,selective catalytic reduction by CO(CO-SCR)effectively achieves the synergistic removal of both pollut...Basic oxygen furnace steelmaking leads to the production of CO-rich off-gas.When CO and NO are combined in off-gas,selective catalytic reduction by CO(CO-SCR)effectively achieves the synergistic removal of both pollutants.In this paper,CuCe_(0.75)Zr_(0.25)O_(y),MnCe_(0.75)Zr_(0.25)O_(y),and FeCe_(0.75)Zr_(0.25)O_(y) catalysts are prepared and evaluated for their CO-SCR activity,and the results show that the reaction system needs to be anaerobic;thus,the CO-SCR reaction can be dominant.The T_(90) values of CuCe_(0.75)Zr_(0.25)O_(y) and FeCe_(0.75)Zr_(0.25)O_(y) are 200℃ and 223℃,respectively.The activities of these two catalysts are higher than that of MnCe_(0.75)Zr_(0.25)O_(y)(T_(90)=375℃).Linear nitrate and bridged bidentate nitrate are the main intermediate species involved in NO conversion on the catalyst surface,and bidentate CO_(3)^(2-)coordination is the main intermediate species involved in CO conversion on the catalyst surface.CuCe_(0.75)Zr_(0.25)O_(y) has high lattice oxygen mobility and is more likely to react with NO and CO.In the presence of oxygen,most CO is oxidized by O_(2),which increases continuously to 100%,100%,and 98%for CuCe_(0.75)Zr_(0.25)O_(y),FeCe_(0.75)Zr_(0.25)O_(y),and MnCe_(0.75)Zr_(0.25)O_(y),respectively;additionally,CO is oxidized by O_(2),and the CO-SCR reaction cannot be carried out.展开更多
Structural reconstruction of nanomaterials offers a fantastic way to regulate the electronic structure of active sites and promote their catalytic activities.However,how to properly facilitate surface reconstruction t...Structural reconstruction of nanomaterials offers a fantastic way to regulate the electronic structure of active sites and promote their catalytic activities.However,how to properly facilitate surface reconstruction to overcome large overpotential that stimulate the surface reconstruction has remained elusive.Herein,we adopt a facile approach to activate surface reconstruction on Ni(OH)_(2) by incorporating F anions to achieve electro-derived structural oxidation process and further boost its oxygen evolution reaction(OER)activity.Ex situ Raman and X-ray photoemission spectroscopy studies indicate that F ions incorporation facilitated surface reconstruction and promotes the original Ni(OH)_(2)transformed into a mesoporous and amorphous F-NiOOH layer during the electrochemical process.Density functional theory(DFT)calculation reveals that this self-reconstructed NiOOH induces a space-charge effect on the p-n junction interface,which not only promotes the absorption of intermediates species(^(*)OH,^(*)O,and^(*)OOH)and charge-transfer process during catalysis,but also leads to a strong interaction of the p-n junction interface to stabilize the materials.This work opens up a new possibility to regulate the electronic structure of active sites and promote their catalytic activities.展开更多
The d-band centers of catalysts have exhibited excellent performance in various reactions.Among them,the enhanced catalytic reaction is considered a crucial way to power dynamics and reduce the“shuttle”effect in pol...The d-band centers of catalysts have exhibited excellent performance in various reactions.Among them,the enhanced catalytic reaction is considered a crucial way to power dynamics and reduce the“shuttle”effect in polysulfide conversions of lithium-sulfur batteries.Here,we report two-dimensional-shaped tungsten borides(WB)nanosheets with d-band centers,where the d orbits of W atoms on the(001)facets show greatly promoting the electrocatalytic sulfur reduction reaction.As-prepared WB-based Li-S cells exhibit excellent electrochemical performance for Li-ion storage.Especially,it delivers superior capacities of 7.7 mAh/cm^(2) under the 8.0 mg/cm^(2) sulfur loading,which is far superior to most other electrode catalysts.This study provides insights into the d-band centers as a promising catalyst of twodimensional boride materials.展开更多
The elucidation of the selective catalytic reduction mechanisms over state-of-the-art metal-promoted zeolites is essential for nitric oxides removal in automobile and stationary source applications.In this work,H/ZSM-...The elucidation of the selective catalytic reduction mechanisms over state-of-the-art metal-promoted zeolites is essential for nitric oxides removal in automobile and stationary source applications.In this work,H/ZSM-5 catalysts modified with transition metals,including copper,manganese,and nickel,were prepared by using an incipient wetness impregnation method and were evaluated for the selective reduction of nitric oxides with ammonia.Results indicate that copper/ZSM-5 exhibits the highest catalytic activity,with>90%nitric oxide conversion at a broad operation temperature window(221–445◦C).The nitric oxide conversion profiles of nickel/ZSM-5 shows two peaks that correspond to weak activity among the catalysts;the low-temperature peak(290◦C)was induced by nickel clusters dispersed on the ZSM-5 surface,while the high-temperature peak(460◦C)was assigned to the bulk nickel oxides.The size of granular nickel monoxide crystallites with an exposed(202)plane is 2–30 nm,as confirmed by Scanning electron microscopy,X-ray diffraction,and Transmission electron microscope measurements.Temperature-programmed reductions with hydrogen results testified that the copper and nickel cations,as the main species contributing to selective catalytic reduction,were reduced via Cu^(2+)/Cu^(+)→Cu^(0) and Ni^(2+)→Ni^(0) for copper/ZSM-5 and nickel/ZSM-5,respectively,while for the manganese/ZSM5,the Mn3+species in manganese clusters were reduced to Mn^(2+) by hydrogen.Particularly,temperatureprogrammed desorption coupled with mass spectrometer(TPD-MS)and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)were comprehensively used to reveal the relationship between zeolite structure and catalysts’properties for improving selective catalytic reduction.These results confirm that the ammonia is adsorbed and activated on both Brønsted and Lewis acid sites.The nitrous oxide desorbs in two stages during nitric oxide-TPD-MS measurements,corresponding to the desorption of nitric oxide bounded to amorphous clusters and the nitric oxide strongly bounded to bulk metal oxides,respectively.The selective catalytic reduction process follows the L-H mechanism at low temperatures,in which nitric oxide and ammonia molecules were adsorbed and activated on the catalyst surface.The selective catalytic reduction rates reached the maximum value of 1.8×10^(8)(218◦C),6.4×10^(7)(227◦C),and 3.9×10^(7)s^(−1)(235◦C)for copper,manganese,and nickel/ZSM-5,respectively.展开更多
基金University of Macao,Grant/Award Numbers:MYRG2018-00192-IAPME,MYRG2020-00187-IAPMEScience and Technology Development Fund,Macao SAR,Grant/Award Numbers:0021/2019/AIR,0041/2019/A1,0046/2019/AFJ,0191/2017/A3UEA funding。
文摘Simultaneously enhancing the reaction kinetics,mass transport,and gas release during alkaline hydrogen evolution reaction(HER)is critical to minimizing the reaction polarization resistance,but remains a big challenge.Through rational design of a hierarchical multiheterogeneous three-dimensionally(3D)ordered macroporous Mo_(2)C-embedded nitrogen-doped carbon with ultrafine Ru nanoclusters anchored on its surface(OMS Mo_(2)C/NC-Ru),we realize both electronic and morphologic engineering of the catalyst to maximize the electrocatalysis performance.The formed Ru-NC heterostructure shows regulative electronic states and optimized adsorption energy with the intermediate H*,and the Mo_(2)C-NC heterostructure accelerates the Volmer reaction due to the strong water dissociation ability as confirmed by theoretical calculations.Consequently,superior HER activity in alkaline solution with an extremely low overpotential of 15.5 mV at 10 mAcm^(−2)with the mass activity more than 17 times higher than that of the benchmark Pt/C,an ultrasmall Tafel slope of 22.7 mV dec−1,and excellent electrocatalytic durability were achieved,attributing to the enhanced mass transport and favorable gas release process endowed from the unique OMS Mo_(2)C/NC-Ru structure.By oxidizing OMS Mo_(2)C/NC-Ru into OMS MoO_(3)-RuO_(2)catalyst,it can also be applied as efficient oxygen evolution electrocatalyst,enabling the construction of a quasi-symmetric electrolyzer for overall water splitting.Such a device's performance surpassed the state-of-the-art Pt/C||RuO2 electrolyzer.This study provides instructive guidance for designing 3D-ordered macroporous multicomponent catalysts for efficient catalytic applications.
基金This study was funded by the Science and Technology Development Fund,Macao SAR(File no.0191/2017/A3,0041/2019/A1,0046/2019/AFJ,0021/2019/AIR)the University of Macao(File no.MYRG2017-00216-FST and MYRG2018-00192-IAPME)+2 种基金the UEA funding,Science and Technology Program of Guangzhou(2019050001)the National Key Research and Development Program of China(2019YFE0198000)Fuming Chen acknowledges the Pearl River Talent Program(2019QN01L951).
文摘Aluminum-metal batteries show great potential as next-generation energy storage due to their abundant resources and intrinsic safety.However,the crucial limitations of metallic Al anodes,such as dendrite and corrosion problems in conventional aluminum-metal batteries,remain challenging and elusive.Here,we report a novel electrodeposition strategy to prepare an optimized 3D Al anode on carbon cloth with an uniform deposition morphology,low local current density,and mitigatory volume change.The symmetrical cells with the 3D Al anode show superior stable cycling(>450 h)and low-voltage hysteresis(~170 mV)at 0.5 mA cm^(−2).High reversibility(~99.7%)is achieved for the Al plating/stripping.The graphite||Al‐4/CC full batteries show a long lifespan of 800 cycles with 54 mAh g^(−1) capacity at a high current density of 1000 mA g^(−1),benefiting from the high capacitive-controlled distribution.This study proposes a novel strategy to design 3D Al anodes for metallic-Al-based batteries by eliminating the problems of planar Al anodes and realizing the potential applications of aluminum-graphite batteries.
基金supported by the funding from Qilu University of Technology(Shandong Academy of Sciences)the Science and Technology Development Fund,Macao SAR(File No.191/2017/A3,041/2019/A1,046/2019/AFJ,0021/2019/AIR)+2 种基金the National Natural Science Foundation of China(Grant No.51972180)the Multi-Year Research Grants(Nos.MYRG2017-00216-FST and MYRG2018-00192-IAPME)from the Research Services and Knowledge Transfer Office at the University of MacaoUEA funding.
文摘CoPS nanoparticles encapsulated with S,P,N tri-doped carbon material(SPNC)were proposed as bifunctional electrocatalyst of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)derived from zeolitic imidazolate framework-67.Density functional theory calculations consistently revealed that P element in CoPS@SPNC improves the electrical conductivity and reduces OH^(*)hydrogenation energy barrier on Co sites,thereby facilitating the overall ORR/OER activities.A flexible Zn–air battery with CoPS@SPNC delivered an overpotential of 0.49 V,an energy efficiency above 80%,and a discharge voltage of 1.29 V at 2 mA cm^(-2) for 80 h.
基金supported by the National Natural Science Foundation of China(Grant No.51475397)Natural Science Foundation of Fujian Province of China(Grant No.2017J06015)the Fundamental Research Fund for Central Universities,Xiamen University,China(Grant No.20720180057)
文摘Microchannel reactors usually have some microchannels with characteristic sizes(i.e., between 1 and 1000 μm). Small channel size and diversity are usually patterned in a microchannel reactor, and these features increase the surface area-to-volume ratio and driving force for heat and mass transport. Microchannel reactors are widely used in the petrochemistry, aerospace, electronics, information technology, and automotive industries, among others. According to the geometric shape of microchannels, a microchannel reactor can be classified as parallel, curved, micro-pin-fin array, bionic, or 3D network type. This review summarizes the fabrication methods of microchannel reactors, including traditional mechanical processing, chemical etching, electroforming injection molding technology, non-traditional machining, and sintering. It also presents the various applications of microchannel reactors in catalytic reactions, heat transfer, mixing, and other areas. Finally, this review describes the development and application prospects of microchannel reactors.
基金supported by the research fund of Hanyang University (HY-2013 year)
文摘Catalytic ozonation is progressively becoming an attractive technique for quick water purification but efficient and stable catalysts remains elusive. Here we solvothermally synthesized highly-dispersed Co3O4 nanocrystals over microscale nitrogen-doping graphene （NG） nanosheets and tested it as a synthetic catalyst in the ozonation of phenol in aqueous solutions. Transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were used to determine its morphology, crystallinity, elemental composition and molecular bonds, respectively. The comparative experiments confirmed the highest catalytic activity and oxidation degree （AOSC） of Co3O4/NG among four nanocomposites （G, NG, Co3O4/G, and Co3OJNG）. Co3O4/NG also has exhibited the highest degradation rate： complete conversion of a near-saturated concentration of phenol （941.1 mg/L） was achieved within 30 min under ambient conditions with only a small dosage of Co3O4/NG （50 mg/L） and ozone （4 mg/L, flow rate： 0.5 L/min）. It also resulted in 34.6% chemical oxygen demand （CODcr） and 24.2% total organic carbon （TOC） reduction. In this work, graphene nanosheets not only functioned as a support for Co3O4 nanocrystals but also functioned as a co-catalyst for the enhancement in phenol removal efficiency. The surface nitridation and Co3O4 modification treatment further improved the removal rate of the phenol pollutants and brought in the higher oxidation degree. Our finding may open new perspectives for pursuing exceptional activity for catalytic ozonation reaction.
基金financially supported by the National Natural Science Foundation of China(51776216)The Science and Technology Development Fund,Macao SAR(File no.0041/2019/A1 and 0046/2019/AFJ)+1 种基金University of Macao(File no.MYRG2017-00216-FST)University of Macao(File no.MYRG2018-00192-IAPME).
文摘Basic oxygen furnace steelmaking leads to the production of CO-rich off-gas.When CO and NO are combined in off-gas,selective catalytic reduction by CO(CO-SCR)effectively achieves the synergistic removal of both pollutants.In this paper,CuCe_(0.75)Zr_(0.25)O_(y),MnCe_(0.75)Zr_(0.25)O_(y),and FeCe_(0.75)Zr_(0.25)O_(y) catalysts are prepared and evaluated for their CO-SCR activity,and the results show that the reaction system needs to be anaerobic;thus,the CO-SCR reaction can be dominant.The T_(90) values of CuCe_(0.75)Zr_(0.25)O_(y) and FeCe_(0.75)Zr_(0.25)O_(y) are 200℃ and 223℃,respectively.The activities of these two catalysts are higher than that of MnCe_(0.75)Zr_(0.25)O_(y)(T_(90)=375℃).Linear nitrate and bridged bidentate nitrate are the main intermediate species involved in NO conversion on the catalyst surface,and bidentate CO_(3)^(2-)coordination is the main intermediate species involved in CO conversion on the catalyst surface.CuCe_(0.75)Zr_(0.25)O_(y) has high lattice oxygen mobility and is more likely to react with NO and CO.In the presence of oxygen,most CO is oxidized by O_(2),which increases continuously to 100%,100%,and 98%for CuCe_(0.75)Zr_(0.25)O_(y),FeCe_(0.75)Zr_(0.25)O_(y),and MnCe_(0.75)Zr_(0.25)O_(y),respectively;additionally,CO is oxidized by O_(2),and the CO-SCR reaction cannot be carried out.
基金This work was funded by the Science and Technology Development Fund,Macao SAR(Nos.0191/2017/A3,0041/2019/A1,0046/2019/AFJ,and 0021/2019/AIR)University of Macao(Nos.MYRG2017-00216-FST and MYRG2018-00192-IAPME)+3 种基金UEA funding,the National Natural Science Foundation of China(Nos.51773211 and 21961160700)the Beijing Municipal Science&Technology Commission,the IBS(IBS-R019-D1)the State Key Laboratory of Organic-Inorganic Composites(OIC)(No.202101002)The DFT calculations were performed at High Performance Computing Cluster(HPCC)of Information and Communication Technology Office(ICTO)at University of Macao.
文摘Structural reconstruction of nanomaterials offers a fantastic way to regulate the electronic structure of active sites and promote their catalytic activities.However,how to properly facilitate surface reconstruction to overcome large overpotential that stimulate the surface reconstruction has remained elusive.Herein,we adopt a facile approach to activate surface reconstruction on Ni(OH)_(2) by incorporating F anions to achieve electro-derived structural oxidation process and further boost its oxygen evolution reaction(OER)activity.Ex situ Raman and X-ray photoemission spectroscopy studies indicate that F ions incorporation facilitated surface reconstruction and promotes the original Ni(OH)_(2)transformed into a mesoporous and amorphous F-NiOOH layer during the electrochemical process.Density functional theory(DFT)calculation reveals that this self-reconstructed NiOOH induces a space-charge effect on the p-n junction interface,which not only promotes the absorption of intermediates species(^(*)OH,^(*)O,and^(*)OOH)and charge-transfer process during catalysis,but also leads to a strong interaction of the p-n junction interface to stabilize the materials.This work opens up a new possibility to regulate the electronic structure of active sites and promote their catalytic activities.
基金supported by the National Natural Science Foundation of China(Nos.61904080,22205101)the Natural Science Foundation of Jiangsu Province(No.BK20190670)+5 种基金the Natural Science Foundation of Colleges and Universities in Jiangsu Province(No.19KJB530008)the Macao Young Scholars Program(No.AM2020005)the High-Performance Computing Cluster(HPCC)of Information and Communication Technology Office(ICTO)at University of Macao,Science and Technology Development Fund,Macao SAR(Nos.0191/2017/A3,0041/2019/A1,0046/2019/AFJ,0021/2019/AIR)University of Macao(Nos.MYRG2017-00216-FST and MYRG2018-00192-IAPME),FDCT Funding Scheme for Postdoctoral Researchers(No.0026/APD/2021)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the UEA funding,and Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110994).
文摘The d-band centers of catalysts have exhibited excellent performance in various reactions.Among them,the enhanced catalytic reaction is considered a crucial way to power dynamics and reduce the“shuttle”effect in polysulfide conversions of lithium-sulfur batteries.Here,we report two-dimensional-shaped tungsten borides(WB)nanosheets with d-band centers,where the d orbits of W atoms on the(001)facets show greatly promoting the electrocatalytic sulfur reduction reaction.As-prepared WB-based Li-S cells exhibit excellent electrochemical performance for Li-ion storage.Especially,it delivers superior capacities of 7.7 mAh/cm^(2) under the 8.0 mg/cm^(2) sulfur loading,which is far superior to most other electrode catalysts.This study provides insights into the d-band centers as a promising catalyst of twodimensional boride materials.
基金the support of National Nature Science Foundation of China(No.51736010)China Scholarship Council(No.202004910623)We sincerely thank Prof.Lv Gang(Tianjin University)for the reasonable suggestions about SCR reaction mechanism,and the Key Projects of Tianjin Natural Science Foundation(19JCZDJC40100).
文摘The elucidation of the selective catalytic reduction mechanisms over state-of-the-art metal-promoted zeolites is essential for nitric oxides removal in automobile and stationary source applications.In this work,H/ZSM-5 catalysts modified with transition metals,including copper,manganese,and nickel,were prepared by using an incipient wetness impregnation method and were evaluated for the selective reduction of nitric oxides with ammonia.Results indicate that copper/ZSM-5 exhibits the highest catalytic activity,with>90%nitric oxide conversion at a broad operation temperature window(221–445◦C).The nitric oxide conversion profiles of nickel/ZSM-5 shows two peaks that correspond to weak activity among the catalysts;the low-temperature peak(290◦C)was induced by nickel clusters dispersed on the ZSM-5 surface,while the high-temperature peak(460◦C)was assigned to the bulk nickel oxides.The size of granular nickel monoxide crystallites with an exposed(202)plane is 2–30 nm,as confirmed by Scanning electron microscopy,X-ray diffraction,and Transmission electron microscope measurements.Temperature-programmed reductions with hydrogen results testified that the copper and nickel cations,as the main species contributing to selective catalytic reduction,were reduced via Cu^(2+)/Cu^(+)→Cu^(0) and Ni^(2+)→Ni^(0) for copper/ZSM-5 and nickel/ZSM-5,respectively,while for the manganese/ZSM5,the Mn3+species in manganese clusters were reduced to Mn^(2+) by hydrogen.Particularly,temperatureprogrammed desorption coupled with mass spectrometer(TPD-MS)and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)were comprehensively used to reveal the relationship between zeolite structure and catalysts’properties for improving selective catalytic reduction.These results confirm that the ammonia is adsorbed and activated on both Brønsted and Lewis acid sites.The nitrous oxide desorbs in two stages during nitric oxide-TPD-MS measurements,corresponding to the desorption of nitric oxide bounded to amorphous clusters and the nitric oxide strongly bounded to bulk metal oxides,respectively.The selective catalytic reduction process follows the L-H mechanism at low temperatures,in which nitric oxide and ammonia molecules were adsorbed and activated on the catalyst surface.The selective catalytic reduction rates reached the maximum value of 1.8×10^(8)(218◦C),6.4×10^(7)(227◦C),and 3.9×10^(7)s^(−1)(235◦C)for copper,manganese,and nickel/ZSM-5,respectively.
