Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride cat...Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride catalysts,theγ-Mo_(2)N exhibits superior activity to target product CO,which is 4.6 and 76 times higher than the other two counterparts ofβ-W_(2)N andδ-NbN at 600℃,respectively.Additionally,γ-Mo_(2)N exhibits excellent stability on both cyclic heating-cooling and high space velocity steady state operation.The deactivation degree of cyclic heating-cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%.In-situ XRD and kinetic studies suggest that theγ-Mo_(2)N itself is able to activate both of the reactants CO_(2)and H_(2).Below 400℃,the reaction mainly occurs at the surface ofγ-Mo_(2)N catalyst.CO_(2)and H_(2)competitively adsorbe on the surface of catalyst and CO_(2)is the relatively stronger surface adsorbate.At a higher temperature,the interstitial vacancies of theγ-Mo_(2)N can be reversibly filled with the oxygen from CO_(2)dissociation.Both of the surface and bulk phase sites ofγ-Mo_(2)N participate in the high temperature CO_(2)hydrogenation pathway.展开更多
Electrochemical nitrogen reduction reaction(NRR) to produce ammonia under ambient conditions is considered as a promising approach to tackle the energy-intensive Haber-Bosch process,but the low Faradaic efficiency and...Electrochemical nitrogen reduction reaction(NRR) to produce ammonia under ambient conditions is considered as a promising approach to tackle the energy-intensive Haber-Bosch process,but the low Faradaic efficiency and yield of NH_3 are still a challenge.Herein,a carbon-vacancies enriched mesoporous g-C_3 N_4 is developed by an in situ Zr doping strategy.The in situ mesoporous-forming mechanism is deeply understood by TPSR to reveal the functions of Zr dopant that pulls C from the precursor of C_3 N_4,resulting the formation of homogeneous mesopores with about 57% of the one C-defective s-triazine ring in C_3 N_4.Due to the defect sites obtained in metal doping synthesis,the RuAu bimetallic supported catalyst(RuAu_3/0.3 Zr-C_3 N_4) exhibits effective NRR performance with a Faraday efficiency of 11.54% and an NH_3 yield of 5.28 μg h^(-1) mg_(cat) ^(-1).at-0.1 V(RHE),which is nearly 10 times higher than that of RuAu_3/C_3 N_4 catalyst.This work proposes a simple and template-free preparation method for the high defect density mesoporous C_3 N_4,and provides new possibilities of a wide application of mesopore g-C3 N4.展开更多
Production of’renewable Methane’has attracted renewed research interest as a fundamental probe reaction and process for CO_(2)utilization through potential use in Cl fuel production and even for future space explora...Production of’renewable Methane’has attracted renewed research interest as a fundamental probe reaction and process for CO_(2)utilization through potential use in Cl fuel production and even for future space exploration technologies.CO_(2)methanation is a structure sensitive reaction on Ni/CeO_(2)catalysts.To precisely elucidate the size effect of the Ni metal center on the CO_(2)methanation performance,we prepared2%Ni/CeO_(2)catalysts with pre-synthesized uniform Ni particles(2,4 and 8 nm)on a high surface area CeO_(2)support.Transmission electron microscopy(TEM)and ambient pressure X-ray photo spectroscopy(AP-XPS)characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions.The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts,and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts,respectively.The DRIFTS studies revealed that the larger Ni(8 nm particles)over CeO_(2)efficiently facilitated the hydrogenation of the surface formate intermediates,which is proposed as the rate determining step accounting for the excellent CO_(2)methanation performance.展开更多
Background: The clinical characteristics of patients with the comorbidities of hypertension and coronary artery disease (HT-CAD) and atrial fibrillation (AF) are largely unknown. This study aimed to investigate the pr...Background: The clinical characteristics of patients with the comorbidities of hypertension and coronary artery disease (HT-CAD) and atrial fibrillation (AF) are largely unknown. This study aimed to investigate the prevalence of AF in patients with HT-CAD and clinical characteristics of patients with both HT-CAD and AF. Methods: This cross-sectional study was conducted in Chinese People’s Liberation Army General Hospital in Beijing, China, and included 20,747 inpatients with HT-CAD with or without AF from August 2008 to July 2018. We examined the overall prevalence, clinical characteristics, comorbidity profiles, treatment patterns, and blood pressure (BP) control of patients with both HT-CAD and AF. Multivariate logistic regression was used to investigate the associations of cardiovascular risk factors with AF in patients with HT-CAD. Results: The overall prevalence of AF in patients with HT-CAD was 4.87% (1011/20,747), and this increased with age;to be specific, the prevalence in women and men increased from 0.78% (2/255) and 1.02% (26/2561) at the age of <50 years to 8.73% (193/2210) and 10.28 % (298/2900) at the age of ≥70 years, respectively. HT-CAD patients who had AF had a higher prevalence of cardiovascular-related comorbidities than those without AF. Multivariate logistic regression showed that age, gender (male), body mass index, heart failure, and chronic kidney disease were independently associated with the risk of AF in patients with HT-CAD. For those with both HT-CAD and AF, 73.49% (743/1011) had a CHA 2 DS 2 -VASc score of ≥4, and only about half of them had the BP controlled at <140/90 mmHg, which indicated a high risk of thromboembolism and stroke. The use of oral anticoagulation increased during the study period (10.00% [20/200] in 2008 to 2011 vs. 30.06% [159/529] in 2015 to 2018, P < 0.01), but remained at a relatively low level. Conclusions: AF is highly prevalent among patients with HT-CAD. Patients with both HT-CAD and AF have a higher prevalence of cardiovascular-related comorbidities, lower BP control rate, and lower use of oral anticoagulation.展开更多
Constructing and understanding the doping effect of secondary metal in transition metal carbide(TMC)catalysts is pivotal for the design of low-cost hydrogen evolution reaction(HER) electrocatalysts. In this work, we d...Constructing and understanding the doping effect of secondary metal in transition metal carbide(TMC)catalysts is pivotal for the design of low-cost hydrogen evolution reaction(HER) electrocatalysts. In this work, we developed a wet-chemistry strategy for synthesizing Co-modified Fe_5C_2 nanoparticles((Fe_(1-x)Cox)_5C_2 NPs) as highly active HER electrocatalysts in basic solution. The structure of(Fe_(1-x)Cox)_5C_2 NPs was characterized by X-ray diffraction(XRD), extended X-ray absorption fine structure spectra(EXAFS) and scanning/transmission electron microscopy(S/TEM), indicating that the isomorphous substitution of cobalt in the lattice of Fe_5C_2.(Fe_(0.75) Co_(0.25))_5C_2 exhibited the best HER activity(174 mV for j = -10 mA/cm^2). Computational calculation results indicate that Co provides the most active site for HER. X-ray adsorption spectra(XAS) studies further suggested that the electron transfer in Fe–C bonds are enhanced by the substitution of Co, which modulates the hydrogen adsorption on the adjacent electronic-enriched carbon, and therefore promotes HER activity. Our results affirm the design of lowcost bimetallic TMCs based HER catalysts.展开更多
Despite the extensive study of the Fe-based Fischer-Tropsch synthesis(FTS)over the past 90 years,its active phases and reaction mechanisms are still unclear due to the coexistence of metals,oxides,and carbide phases p...Despite the extensive study of the Fe-based Fischer-Tropsch synthesis(FTS)over the past 90 years,its active phases and reaction mechanisms are still unclear due to the coexistence of metals,oxides,and carbide phases presented under realistic FTS reaction conditions and the complex reaction network involving CO activation,C-C coupling,and methane formation.To address these issues,we successfully synthesized a range of pure-phase iron and iron-carbide nanoparticles(Fe,Fe_(5)C_(2),Fe_(3)C,and Fe_(7)C_(3))for the first time.By using them as the ideal model catalysts on high-pressure transient experiments,we identified unambiguously that all the iron carbides are catalytically active in the FTS reaction while Fe_(5)C_(2) is the most active yet stable carbide phase,consistent with density functional theory(DFT)calculation results.The reaction mechanism and kinetics of Fe-based FTS were further explored on the basis of those model catalysts by means of transient high-pressure stepwise temperature-programmed surface reaction(STPSR)experiments and DFT calculations.Our work provides new insights into the active phase of iron carbides and corresponding FTS reaction mechanism,which is essential for better iron-based catalyst design for FTS reactions.展开更多
基金financially supported by the National Natural Science Foundation of China(22002140)Zhejiang Provincial Natural Science Foundation of China(LR21B030001 and LR22b030003)+1 种基金Young Elite Scientist Sponsorship Program by CAST(No.2019QNRC001)Use of the Advanced Photon Source(beamlines 17-BM,for in-situ XRD characterization)was supported by the U.S.DOE under contract no.DE-AC02-06CH11357。
文摘Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride catalysts,theγ-Mo_(2)N exhibits superior activity to target product CO,which is 4.6 and 76 times higher than the other two counterparts ofβ-W_(2)N andδ-NbN at 600℃,respectively.Additionally,γ-Mo_(2)N exhibits excellent stability on both cyclic heating-cooling and high space velocity steady state operation.The deactivation degree of cyclic heating-cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%.In-situ XRD and kinetic studies suggest that theγ-Mo_(2)N itself is able to activate both of the reactants CO_(2)and H_(2).Below 400℃,the reaction mainly occurs at the surface ofγ-Mo_(2)N catalyst.CO_(2)and H_(2)competitively adsorbe on the surface of catalyst and CO_(2)is the relatively stronger surface adsorbate.At a higher temperature,the interstitial vacancies of theγ-Mo_(2)N can be reversibly filled with the oxygen from CO_(2)dissociation.Both of the surface and bulk phase sites ofγ-Mo_(2)N participate in the high temperature CO_(2)hydrogenation pathway.
基金supported by the National Natural Science Foundation of China (No. 21978259)the Zhejiang Provincial Natural Science Foundation of China (No. LR17B060002)the Fundamental Research Funds for the Central Universities。
文摘Electrochemical nitrogen reduction reaction(NRR) to produce ammonia under ambient conditions is considered as a promising approach to tackle the energy-intensive Haber-Bosch process,but the low Faradaic efficiency and yield of NH_3 are still a challenge.Herein,a carbon-vacancies enriched mesoporous g-C_3 N_4 is developed by an in situ Zr doping strategy.The in situ mesoporous-forming mechanism is deeply understood by TPSR to reveal the functions of Zr dopant that pulls C from the precursor of C_3 N_4,resulting the formation of homogeneous mesopores with about 57% of the one C-defective s-triazine ring in C_3 N_4.Due to the defect sites obtained in metal doping synthesis,the RuAu bimetallic supported catalyst(RuAu_3/0.3 Zr-C_3 N_4) exhibits effective NRR performance with a Faraday efficiency of 11.54% and an NH_3 yield of 5.28 μg h^(-1) mg_(cat) ^(-1).at-0.1 V(RHE),which is nearly 10 times higher than that of RuAu_3/C_3 N_4 catalyst.This work proposes a simple and template-free preparation method for the high defect density mesoporous C_3 N_4,and provides new possibilities of a wide application of mesopore g-C3 N4.
基金supported by the U.S.Department of Energy under contract no.DE-SC0012704supported by a U.S.Department of Energy Early Career Award+2 种基金ICREA Academia program and projects MICINN/FEDER RTI2018093996-B-C31 and GC 2017 SGR 128financial support from the Natural Science Foundation of China(22002140)Young Elite Scientist Sponsorship Program by CAST,NO.2019QNRC001。
文摘Production of’renewable Methane’has attracted renewed research interest as a fundamental probe reaction and process for CO_(2)utilization through potential use in Cl fuel production and even for future space exploration technologies.CO_(2)methanation is a structure sensitive reaction on Ni/CeO_(2)catalysts.To precisely elucidate the size effect of the Ni metal center on the CO_(2)methanation performance,we prepared2%Ni/CeO_(2)catalysts with pre-synthesized uniform Ni particles(2,4 and 8 nm)on a high surface area CeO_(2)support.Transmission electron microscopy(TEM)and ambient pressure X-ray photo spectroscopy(AP-XPS)characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions.The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts,and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts,respectively.The DRIFTS studies revealed that the larger Ni(8 nm particles)over CeO_(2)efficiently facilitated the hydrogenation of the surface formate intermediates,which is proposed as the rate determining step accounting for the excellent CO_(2)methanation performance.
基金Capital Health Research and Development of Special,Beijing Health Commission(No.2020-2-5013)National Natural Science Foundation of China(No.82070433)
文摘Background: The clinical characteristics of patients with the comorbidities of hypertension and coronary artery disease (HT-CAD) and atrial fibrillation (AF) are largely unknown. This study aimed to investigate the prevalence of AF in patients with HT-CAD and clinical characteristics of patients with both HT-CAD and AF. Methods: This cross-sectional study was conducted in Chinese People’s Liberation Army General Hospital in Beijing, China, and included 20,747 inpatients with HT-CAD with or without AF from August 2008 to July 2018. We examined the overall prevalence, clinical characteristics, comorbidity profiles, treatment patterns, and blood pressure (BP) control of patients with both HT-CAD and AF. Multivariate logistic regression was used to investigate the associations of cardiovascular risk factors with AF in patients with HT-CAD. Results: The overall prevalence of AF in patients with HT-CAD was 4.87% (1011/20,747), and this increased with age;to be specific, the prevalence in women and men increased from 0.78% (2/255) and 1.02% (26/2561) at the age of <50 years to 8.73% (193/2210) and 10.28 % (298/2900) at the age of ≥70 years, respectively. HT-CAD patients who had AF had a higher prevalence of cardiovascular-related comorbidities than those without AF. Multivariate logistic regression showed that age, gender (male), body mass index, heart failure, and chronic kidney disease were independently associated with the risk of AF in patients with HT-CAD. For those with both HT-CAD and AF, 73.49% (743/1011) had a CHA 2 DS 2 -VASc score of ≥4, and only about half of them had the BP controlled at <140/90 mmHg, which indicated a high risk of thromboembolism and stroke. The use of oral anticoagulation increased during the study period (10.00% [20/200] in 2008 to 2011 vs. 30.06% [159/529] in 2015 to 2018, P < 0.01), but remained at a relatively low level. Conclusions: AF is highly prevalent among patients with HT-CAD. Patients with both HT-CAD and AF have a higher prevalence of cardiovascular-related comorbidities, lower BP control rate, and lower use of oral anticoagulation.
基金supported by the National Natural Science Foundation of China(91645115,21473003,21673273,21473229,21821004,and 91545121)the National Basic Research Program of China(2013CB933100)+4 种基金the financial support of China Postdoctoral Science Foundation(2016M590216)the financial support of China Postdoctoral Science Foundation(2015M580011)National Thousand Young Talents Program of ChinaHundred-Talent Program of Chinese Academy of SciencesShanxi Hundred-Talent Program
文摘Constructing and understanding the doping effect of secondary metal in transition metal carbide(TMC)catalysts is pivotal for the design of low-cost hydrogen evolution reaction(HER) electrocatalysts. In this work, we developed a wet-chemistry strategy for synthesizing Co-modified Fe_5C_2 nanoparticles((Fe_(1-x)Cox)_5C_2 NPs) as highly active HER electrocatalysts in basic solution. The structure of(Fe_(1-x)Cox)_5C_2 NPs was characterized by X-ray diffraction(XRD), extended X-ray absorption fine structure spectra(EXAFS) and scanning/transmission electron microscopy(S/TEM), indicating that the isomorphous substitution of cobalt in the lattice of Fe_5C_2.(Fe_(0.75) Co_(0.25))_5C_2 exhibited the best HER activity(174 mV for j = -10 mA/cm^2). Computational calculation results indicate that Co provides the most active site for HER. X-ray adsorption spectra(XAS) studies further suggested that the electron transfer in Fe–C bonds are enhanced by the substitution of Co, which modulates the hydrogen adsorption on the adjacent electronic-enriched carbon, and therefore promotes HER activity. Our results affirm the design of lowcost bimetallic TMCs based HER catalysts.
基金supported by the Natural Science Foundation of China(nos.21725301,91645115,21821004,21932002,51631001,91645202,and 91945302)the National Key R&D Program of China(nos.2017YFB0602200,2017YFB0602205,and 2018YFA0208603)+1 种基金the Natural Science Foundation of Beijing Municipality(no.2191001)the Chinese Academy of Sciences Key Project(no.QYZDJ-SSWSLH054).
文摘Despite the extensive study of the Fe-based Fischer-Tropsch synthesis(FTS)over the past 90 years,its active phases and reaction mechanisms are still unclear due to the coexistence of metals,oxides,and carbide phases presented under realistic FTS reaction conditions and the complex reaction network involving CO activation,C-C coupling,and methane formation.To address these issues,we successfully synthesized a range of pure-phase iron and iron-carbide nanoparticles(Fe,Fe_(5)C_(2),Fe_(3)C,and Fe_(7)C_(3))for the first time.By using them as the ideal model catalysts on high-pressure transient experiments,we identified unambiguously that all the iron carbides are catalytically active in the FTS reaction while Fe_(5)C_(2) is the most active yet stable carbide phase,consistent with density functional theory(DFT)calculation results.The reaction mechanism and kinetics of Fe-based FTS were further explored on the basis of those model catalysts by means of transient high-pressure stepwise temperature-programmed surface reaction(STPSR)experiments and DFT calculations.Our work provides new insights into the active phase of iron carbides and corresponding FTS reaction mechanism,which is essential for better iron-based catalyst design for FTS reactions.
