开发经济高效的析氧反应电催化剂对于推进可充电金属-空气电池和电解水技术的发展至关重要.一般来说,具有完整蜂窝结构的石墨碳基面是电化学惰性的,需要依赖缺陷或者掺杂结构诱导的电荷极化效应来提升催化活性.相比于基面,边缘位点具有...开发经济高效的析氧反应电催化剂对于推进可充电金属-空气电池和电解水技术的发展至关重要.一般来说,具有完整蜂窝结构的石墨碳基面是电化学惰性的,需要依赖缺陷或者掺杂结构诱导的电荷极化效应来提升催化活性.相比于基面,边缘位点具有特殊的局域电子态,为提升石墨碳电极的本征催化活性开辟了新的思路,然而其结构精准构筑目前仍面临极大挑战.本文以“人字形”多壁碳纳米管(H-MWCNTs)作为研究切入点,利用高温熔盐介质主导的插层剥离和截断效应,实现“边缘-平面位点”结构可控构筑,为实现高效电解水析氧反应(OER)提供了重要的结构基础.通过熔盐辅助热解方法可控制备了具有完全暴露的内外边缘平面的目标催化剂H-MWCNTs-MS,并研究其OER催化性能.在碱性介质中10 mA cm^(-2)电流密度所需过电位仅为236 mV,是目前报道的较好的非金属电催化剂.同时,H-MWCNTs-MS在10,50和100 mA cm^(-2)电流密度下均表现出较好的电化学稳定性.利用原位衰减全反射-表面增强红外吸收光谱(ATR-SEIRAS)技术研究了“边缘-平面位点”在OER过程中的结构重构过程,与理论计算分析的高能“边缘态”结果一致,并确定酮氧官能化位点为真实催化活性中心.理论计算结果表明,氧官能团修饰结构能够显著促进电荷的再分配,增强层间耦合作用,降低关键含氧中间体*OOH的形成能垒,加速OER反应动力学.此外,H-MWCNTs-MS的开放式结构极大程度提高了“边缘-平面位点”的利用率,减小的纳米管壁厚促进了层间电荷迁移,也是增强OER活性的关键要素.综上,精准构筑“边缘-平面位点”为开发高效石墨碳电极开辟了新的思路,通过原位谱学技术揭示边缘位点催化结构重构,能够进一步丰富研究者对于电催化协同效应的科学认识.展开更多
Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve ...Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve Hg0 oxidation on SCR catalysts.In this work,the effects of different bromides(NH4Br,NaBr,KBr,and CaBr2)on a commercial V2O5‐WO3/TiO2 catalyst were studied.NOx conversion decreased significantly over the KBr‐poisoned catalyst(denoted as L‐KBr),while that over NaBr‐and CaBr2‐poisoned catalysts(denoted as L‐NaBr and L‐CaBr,respectivity)decreased to a lesser extent compared with the fresh sample.Poor N2 selectivity was observed over L‐NaBr,L‐KBr and L‐CaBr catalysts.The decrease in the ratio of chemisorbed oxygen to total surface oxygen(Oα/(Oα+Oβ+Ow)),reducibility and surface acidity might contribute to the poor activity and N2 selectivity over L‐KBr catalyst.The increased Oαratio was conducive to the enhanced reducibility of L‐CaBr.Combined with enhanced surface acidity,this might offset the negative effect of the loss of active sites by CaBr2 covering.The overoxidation of NH3 and poor N2 selectivity in NH3 oxidation should retard the SCR activity at high temperatures over L‐CaBr catalyst.The increased basicity might contribute to increased NOx adsorption on L‐KBr and L‐CaBr catalysts.A correlation between the acid‐basic and redox properties of bromide‐poisoned catalysts and their catalytic properties is established.展开更多
Electrochemical nitrogen reduction reaction (eNRR) is an alternative promising manner for sustainable N2 fixation with low-emission. The major challenge for developing an efficient electrocatalyst is the cleaving of t...Electrochemical nitrogen reduction reaction (eNRR) is an alternative promising manner for sustainable N2 fixation with low-emission. The major challenge for developing an efficient electrocatalyst is the cleaving of the stable Ntriple bondN triple bonds. Herein, we design a new MoS_(2) with in-plane defect cluster through a bottom-up approach for the first time, where the defect cluster is composed of three adjacent S vacancies. The well-defined in-plane defect clusters could contribute to the strong chemical adsorption and activation towards inert nitrogen, achieving an excellent eNRR performance with an ammonia yield rate of 43.4 ± 3 μg h^(−1) mgcat.^(−1) and a Faradaic efficiency of 16.8 ± 2% at −0.3 V (vs. RHE). The performance is much higher than that of MoS_(2) with the edge defect. Isotopic labeling confirms that N atoms of produced NH4+ originate from N2. Furthermore, the in-plane defect clusters realized the alternate hydrogenation of nitrogen in a side-on way to synthesize ammonia. This work provides a prospecting strategy for fine-tuning in-plane defects in a catalyst, and also promotes the progress of eNRR.展开更多
The metal–support interactions induced by high-temperature hydrogen reduction have a strong influence on the catalytic performance of ceria-supported Ru catalysts. However, the appearance of the strong metal–support...The metal–support interactions induced by high-temperature hydrogen reduction have a strong influence on the catalytic performance of ceria-supported Ru catalysts. However, the appearance of the strong metal–support interaction leads to covering of the Ru species by Ce suboxides, which is detrimental to the ammonia synthesis reaction that requires metallic species as active sites. In the present work, the interaction between Ru and ceria in the Ru/CeO_(2) catalyst was induced by NaBH_(4) treatment. NaBH_(4) treatment enhanced the fraction of metallic Ru, proportion of Ce^(3+), content of exposed Ru species, and amount of surface oxygen species. As a result, a larger amount of hydrogen species would desorb by the H_(2)-formation pathway and the strength of hydrogen adsorption would be weaker, weakening the inhibition effect of the hydrogen species on ammonia synthesis. In addition, the strong electronic metal–support interaction aids in nitrogen dissociation. Consequently, Ru/CeO_(2) with NaBH_(4) treatment showed higher ammonia synthesis rates than that with only hydrogen reduction.展开更多
Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were p...Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were prepared to analyze the effect of Ru surface density on the catalytic performance of Ru/CeCO_(2) for ammonia synthesis.For the Ru/CeCO_(2) catalysts with Ru surface densities lower than 0.68 Ru nm^(-2),the Ru layers were in close contact with CeCO_(2),and electrons were transferred directly from the CeCO_(2) defect sites to the Ru species.In such cases,the adsorption of hydrogen species on the Ru sites in the vicinity of 0 atoms was high,leading to a high ammonia synthesis activity and strong hydrogen poisoning.In contrast,the preferential aggregation of Ru species into large particles on top of the Ru overlayer resulted in the coexistence of Ru clusters and particles,for catalysts with a Ru surface density higher than 1.4 Ru nm^(-2),for which Ru particles were isolated from the direct electronic influence of CeCO_(2).Consequently,the Ru-Ceth interactions were weak,and hydrogen poisoning can be significantly alleviated.Overall,electron transfer and hydrogen adsorption synergistically affected the synthesis of ammonia over Ru/CeCO_(2) catalysts,and catalyst samples with a Ru surface density lower than 0.31 Ru nm^(-2) or exactly 2.1 Ru nm^(-2) exhibited high catalytic activity for ammonia synthesis.展开更多
The industrial manufacture of ammonia(NH_(3))using Fe-based catalyst works under rigorous conditions.For the goal of carbon-neutrality,it is highly desired to develop advanced catalyst for NH_(3)synthesis at mild cond...The industrial manufacture of ammonia(NH_(3))using Fe-based catalyst works under rigorous conditions.For the goal of carbon-neutrality,it is highly desired to develop advanced catalyst for NH_(3)synthesis at mild conditions to reduce energy consumption and CO_(2)emissions.However,the main challenge of NH_(3)synthesis at mild conditions lies in the dissociation of steady N≡N triple bond.In this work,we report the design of subnanometer Ru clusters(0.8 nm)anchored on the hollow N-doped carbon spheres catalyst(Ru-SNCs),which effectively promotes the NH_(3)synthesis at mild conditions via an associative route.The NH_(3)synthesis rate over Ru-SNCs(0.49%(mass)Ru)reaches up to 11.7 mmol NH_(3)·(g cat)^(-1)·h^(-1) at 400℃ and 3 MPa,which is superior to that of 8.3 mmol NH_(3)·(g cat)^(-1)·h^(-1) over Ru nanoparticle catalyst(1.20%(mass)Ru).Various characterizations show that the N_(2)H_(4)species are the main intermediates for NH_(3)synthesis on Ru-SNCs catalyst.It demonstrates that Ru-SNCs catalyst can follow an associative route for N_(2)activation,which circumvents the direct dissociation of N_(2)and results in highly efficient NH_(3)synthesis at mild conditions.展开更多
In the adenine-induced renal failure rats, reversibility of renal failure and recovery of bone mineral density (BMD) by discontinuation of adenine-rich diet were reported: We think that the effect to bone metabolism w...In the adenine-induced renal failure rats, reversibility of renal failure and recovery of bone mineral density (BMD) by discontinuation of adenine-rich diet were reported: We think that the effect to bone metabolism with medication may be able to be evaluated as reinforcement of the BMD recovery. We have so far investigated the Chinese herbal medicine based on Hachimi-jio-gan (HJG) which are more effective than HJG alone. In this study, we investigated the effects of our Chinese herbal prescription on BMD in the adenine-treated rats compared to that of vitamin D3treatment. Young male rats were administrated 100 mg/ml adenine for 8 weeks, and they showed renal failure and bone loss. The adenine-treated rats were divided into the following 3 groups, that is, the group experienced no treatment (control), the group givenour Chinese herbal medicine (HAO), and the group given vitamin D3 (VD3) medication. It is likely that VD3 medication was less effective for increase of the femoral BMD than increase of the spinal BMD. In contrast, HAO was effective for increase of the femoral BMD. The VD3 group showed low deoxypyridinoline (Dpd: bone resorption maker) as compared to the control group.However, the HAO group showed same or slightly high Dpd. It is suggested that VD3 may increase BMD by reduction of bone resorption, while HAO may show effect on BMD by activating bone metabolism. It is indicated that HAO may become a curative medicine for bone loss because of the different target site from vitamin D3.展开更多
Ru-based heterogeneous catalysts have been used in a wide range of important reactions.However,due to the sintering of Ru nanoparticles their practical applications are somewhat restricted.Herein,for the first time we...Ru-based heterogeneous catalysts have been used in a wide range of important reactions.However,due to the sintering of Ru nanoparticles their practical applications are somewhat restricted.Herein,for the first time we report a new and facile strategy to confine Ru and/or Co nanoparticles(NPs) in the channels of N-doped carbon using benzoic acid to guide the deposition location of Ru.The developed catalyst with confined RuCo alloy particles exhibits high resistance against Ru sintering and displays excellent activity and long term stability for NH3 synthesis,achieving an NH3 synthesis rate of up to 18.9 mmol NH_(3) gcat^(-1)h^(-1)at 400℃,which is ca.2.25 times that of the catalyst prepared without confinement(with metal deposited on the support surface).In the latter case,there is an increase of nanoparticle size from 2.52 to 4.25 nm together with ca.48% decrease of NH_(3) synthesis rate after 68 h at 400℃.This study provides a new avenue for simple fabrication of precious-metal-based catalysts that are highly resistant against sintering,specifically suitable for low-temperature synthesis of ammonia with outstanding efficiency.展开更多
Ammonia(NH_(3)) decomposition to release CO_x-free hydrogen(H_(2)) over non-noble catalysts has gained increasing attention.In this study,three nanostructured CeO_(2) with different morphologies,viz.rod(R).sphere(Sph)...Ammonia(NH_(3)) decomposition to release CO_x-free hydrogen(H_(2)) over non-noble catalysts has gained increasing attention.In this study,three nanostructured CeO_(2) with different morphologies,viz.rod(R).sphere(Sph),and spindle(Spi),were fabricated and served as supports for Ni/CeO_(2) catalyst.The CeO_(2)supports are different in particle sizes,specific surface area and porosity,resulting in the formation of Ni nanoparticles with distinguished sizes and dispersions.The surface properties of the Ni/CeO_(2) catalysts are not only distinct but also influential,affecting the adsorption and desorption of NH_(3),N_(2),and/or H_(2)molecules.The Ni/CeO_(2)-R catalyst shows superior catalytic activity compared to the other two,owing to its smaller Ni crystallite size and larger BET surface area.The most abundant strong basic sites are observed for Ni/CeO_(2)-Spi catalyst based on its exposed CeO_(2)(110) planes,which facilitates the donation of electrons to the Ni particles,benefiting the associative desorption of N atoms.Thus,Ni/CeO_(2)-Spi shows higher catalytic activity than Ni/CeO_(2)-Sph,despite their almost identical Ni crystallite sizes.展开更多
The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in t...The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in the renewable energy.Generally,ZrO_(2) was regarded as an inferior support for Ru catalyst used in ammonia synthesis.Here we prepare ZrO_(2) with monoclinic phase and carbon species from ZrCl_(4) following the preparation route of UiO-66 as well as ammonia treatment.Owing to the presence of a larger amount of hydrogen adsorption as well as the easier desorption of hydrogen species,the ill effect of hydrogen species on the nitrogen adsorption-desorption and ammonia synthesis can be effectively alleviated.The resulting ZrO_(2)-supported Ru catalyst showed 4 times higher ammonia synthesis activity than the conventional Ru/ZrO_(2) obtained from zirconium nitrate.展开更多
Fossil fuels still dominate global energy structure in our modern society,and have led to massive CO_(2) emissions.Recently,ammonia has been regarded as a clean energy carrier toward diminishing or even eliminating th...Fossil fuels still dominate global energy structure in our modern society,and have led to massive CO_(2) emissions.Recently,ammonia has been regarded as a clean energy carrier toward diminishing or even eliminating the CO_(2) emissions and has received significant attention.The ammonia can be synthesized from atmospheric dinitrogen and green hydrogen from water electrolysis by renewable energies,and converted back into dinitrogen and water for energy release,as shown in Figure 1.Benefited from the matured ammonia manufacture and transportation throughout the world for over one century,the already existing high-capacity infrastructure helps efficient storage and redistribution of ammonia with lowest economic cost.However,although considerable progress has been made in this artificial nitrogen cycle,there are still many challenges in developing highly-efficient routes and catalysts.Herein,we evaluate the current catalytic routes of ammonia synthesis(including thermocatalytic synthesis,electrocatalytic synthesis and photocatalytic synthesis)and ammonia utilization(involving ammonia decomposition,direct ammonia fuel cells and ammonia combustion).We also discuss the key issue in each process,and anticipate that our viewpoints and opinions could facilitate the developments of artificial nitrogen cycle and energy decarbonization.展开更多
To stabilize Ru nanoparticles against sintering is an urgent problem in the utilization of Ru-based catalysts for NH3 synthesis.In the present study,we used Ru-containing ZSM-5 as seeds to crystallize ZSM-5,and the re...To stabilize Ru nanoparticles against sintering is an urgent problem in the utilization of Ru-based catalysts for NH3 synthesis.In the present study,we used Ru-containing ZSM-5 as seeds to crystallize ZSM-5,and the resulted Ru@ZSM-5 catalyst is highly resistant against Ru sintering.According to the results of diffuse reflectance infrared fourier transform spectroscopy(DRIFTS)and transmission electron microscopy(TEM)analyses,the average size of Ru nanoparticles is around 3.6 nm,which is smaller than that of Ru/ZSM-5-IWI prepared by incipient wetness impregnation.In NH3 synthesis(N2:H2=1:3)at 400℃and 1 MPa,Ru@ZSM-5 displays a formation rate of 5.84 mmolNH3 gcat^-1 h^-1,which is much higher than that of Ru/ZSM-5-IWI(2.13 mmolNH3 gcat^-1 h^-1).According to the results of TEM,N2-temperatureprogrammed desorption(N2-TPD),X-ray photoelectron spectroscopy(XPS)and X-ray absorption fine structure(XAFS)studies,it is deduced that the superior performance of Ru@ZSM-5 is attributable to the small particle size and the ample existence of metallic Ru0 sites.This method of zeolite encapsulation is a feasible way to stabilize Ru nanoparticles for NH3 synthesis.展开更多
文摘开发经济高效的析氧反应电催化剂对于推进可充电金属-空气电池和电解水技术的发展至关重要.一般来说,具有完整蜂窝结构的石墨碳基面是电化学惰性的,需要依赖缺陷或者掺杂结构诱导的电荷极化效应来提升催化活性.相比于基面,边缘位点具有特殊的局域电子态,为提升石墨碳电极的本征催化活性开辟了新的思路,然而其结构精准构筑目前仍面临极大挑战.本文以“人字形”多壁碳纳米管(H-MWCNTs)作为研究切入点,利用高温熔盐介质主导的插层剥离和截断效应,实现“边缘-平面位点”结构可控构筑,为实现高效电解水析氧反应(OER)提供了重要的结构基础.通过熔盐辅助热解方法可控制备了具有完全暴露的内外边缘平面的目标催化剂H-MWCNTs-MS,并研究其OER催化性能.在碱性介质中10 mA cm^(-2)电流密度所需过电位仅为236 mV,是目前报道的较好的非金属电催化剂.同时,H-MWCNTs-MS在10,50和100 mA cm^(-2)电流密度下均表现出较好的电化学稳定性.利用原位衰减全反射-表面增强红外吸收光谱(ATR-SEIRAS)技术研究了“边缘-平面位点”在OER过程中的结构重构过程,与理论计算分析的高能“边缘态”结果一致,并确定酮氧官能化位点为真实催化活性中心.理论计算结果表明,氧官能团修饰结构能够显著促进电荷的再分配,增强层间耦合作用,降低关键含氧中间体*OOH的形成能垒,加速OER反应动力学.此外,H-MWCNTs-MS的开放式结构极大程度提高了“边缘-平面位点”的利用率,减小的纳米管壁厚促进了层间电荷迁移,也是增强OER活性的关键要素.综上,精准构筑“边缘-平面位点”为开发高效石墨碳电极开辟了新的思路,通过原位谱学技术揭示边缘位点催化结构重构,能够进一步丰富研究者对于电催化协同效应的科学认识.
基金supported by the National Key R&D Program of China(2016YFC0203900,2016YFC0203901)National Natural Science Foundation of China(51778619,21577173)~~
文摘Alkali and alkaline‐earth metals from fly ash have a significant deactivation effect on catalysts used for selective catalytic reduction of NOx by NH3(NH3‐SCR).Bromides are considered effective additives to improve Hg0 oxidation on SCR catalysts.In this work,the effects of different bromides(NH4Br,NaBr,KBr,and CaBr2)on a commercial V2O5‐WO3/TiO2 catalyst were studied.NOx conversion decreased significantly over the KBr‐poisoned catalyst(denoted as L‐KBr),while that over NaBr‐and CaBr2‐poisoned catalysts(denoted as L‐NaBr and L‐CaBr,respectivity)decreased to a lesser extent compared with the fresh sample.Poor N2 selectivity was observed over L‐NaBr,L‐KBr and L‐CaBr catalysts.The decrease in the ratio of chemisorbed oxygen to total surface oxygen(Oα/(Oα+Oβ+Ow)),reducibility and surface acidity might contribute to the poor activity and N2 selectivity over L‐KBr catalyst.The increased Oαratio was conducive to the enhanced reducibility of L‐CaBr.Combined with enhanced surface acidity,this might offset the negative effect of the loss of active sites by CaBr2 covering.The overoxidation of NH3 and poor N2 selectivity in NH3 oxidation should retard the SCR activity at high temperatures over L‐CaBr catalyst.The increased basicity might contribute to increased NOx adsorption on L‐KBr and L‐CaBr catalysts.A correlation between the acid‐basic and redox properties of bromide‐poisoned catalysts and their catalytic properties is established.
基金This work was supported by the National Natural Science Foundation of China(22078063,21825801).
文摘Electrochemical nitrogen reduction reaction (eNRR) is an alternative promising manner for sustainable N2 fixation with low-emission. The major challenge for developing an efficient electrocatalyst is the cleaving of the stable Ntriple bondN triple bonds. Herein, we design a new MoS_(2) with in-plane defect cluster through a bottom-up approach for the first time, where the defect cluster is composed of three adjacent S vacancies. The well-defined in-plane defect clusters could contribute to the strong chemical adsorption and activation towards inert nitrogen, achieving an excellent eNRR performance with an ammonia yield rate of 43.4 ± 3 μg h^(−1) mgcat.^(−1) and a Faradaic efficiency of 16.8 ± 2% at −0.3 V (vs. RHE). The performance is much higher than that of MoS_(2) with the edge defect. Isotopic labeling confirms that N atoms of produced NH4+ originate from N2. Furthermore, the in-plane defect clusters realized the alternate hydrogenation of nitrogen in a side-on way to synthesize ammonia. This work provides a prospecting strategy for fine-tuning in-plane defects in a catalyst, and also promotes the progress of eNRR.
基金financially supported by the National Science Foundation of China (Nos. 21776047, 21825801, 21978051)the Program for Qishan Scholar of Fuzhou University (Grant XRC18033)。
文摘The metal–support interactions induced by high-temperature hydrogen reduction have a strong influence on the catalytic performance of ceria-supported Ru catalysts. However, the appearance of the strong metal–support interaction leads to covering of the Ru species by Ce suboxides, which is detrimental to the ammonia synthesis reaction that requires metallic species as active sites. In the present work, the interaction between Ru and ceria in the Ru/CeO_(2) catalyst was induced by NaBH_(4) treatment. NaBH_(4) treatment enhanced the fraction of metallic Ru, proportion of Ce^(3+), content of exposed Ru species, and amount of surface oxygen species. As a result, a larger amount of hydrogen species would desorb by the H_(2)-formation pathway and the strength of hydrogen adsorption would be weaker, weakening the inhibition effect of the hydrogen species on ammonia synthesis. In addition, the strong electronic metal–support interaction aids in nitrogen dissociation. Consequently, Ru/CeO_(2) with NaBH_(4) treatment showed higher ammonia synthesis rates than that with only hydrogen reduction.
文摘Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were prepared to analyze the effect of Ru surface density on the catalytic performance of Ru/CeCO_(2) for ammonia synthesis.For the Ru/CeCO_(2) catalysts with Ru surface densities lower than 0.68 Ru nm^(-2),the Ru layers were in close contact with CeCO_(2),and electrons were transferred directly from the CeCO_(2) defect sites to the Ru species.In such cases,the adsorption of hydrogen species on the Ru sites in the vicinity of 0 atoms was high,leading to a high ammonia synthesis activity and strong hydrogen poisoning.In contrast,the preferential aggregation of Ru species into large particles on top of the Ru overlayer resulted in the coexistence of Ru clusters and particles,for catalysts with a Ru surface density higher than 1.4 Ru nm^(-2),for which Ru particles were isolated from the direct electronic influence of CeCO_(2).Consequently,the Ru-Ceth interactions were weak,and hydrogen poisoning can be significantly alleviated.Overall,electron transfer and hydrogen adsorption synergistically affected the synthesis of ammonia over Ru/CeCO_(2) catalysts,and catalyst samples with a Ru surface density lower than 0.31 Ru nm^(-2) or exactly 2.1 Ru nm^(-2) exhibited high catalytic activity for ammonia synthesis.
基金the Key Research&Development Program of National Natural Science Foundation of China(22038002)the National Natural Science Foundation of China(21972019,22108037)。
文摘The industrial manufacture of ammonia(NH_(3))using Fe-based catalyst works under rigorous conditions.For the goal of carbon-neutrality,it is highly desired to develop advanced catalyst for NH_(3)synthesis at mild conditions to reduce energy consumption and CO_(2)emissions.However,the main challenge of NH_(3)synthesis at mild conditions lies in the dissociation of steady N≡N triple bond.In this work,we report the design of subnanometer Ru clusters(0.8 nm)anchored on the hollow N-doped carbon spheres catalyst(Ru-SNCs),which effectively promotes the NH_(3)synthesis at mild conditions via an associative route.The NH_(3)synthesis rate over Ru-SNCs(0.49%(mass)Ru)reaches up to 11.7 mmol NH_(3)·(g cat)^(-1)·h^(-1) at 400℃ and 3 MPa,which is superior to that of 8.3 mmol NH_(3)·(g cat)^(-1)·h^(-1) over Ru nanoparticle catalyst(1.20%(mass)Ru).Various characterizations show that the N_(2)H_(4)species are the main intermediates for NH_(3)synthesis on Ru-SNCs catalyst.It demonstrates that Ru-SNCs catalyst can follow an associative route for N_(2)activation,which circumvents the direct dissociation of N_(2)and results in highly efficient NH_(3)synthesis at mild conditions.
文摘In the adenine-induced renal failure rats, reversibility of renal failure and recovery of bone mineral density (BMD) by discontinuation of adenine-rich diet were reported: We think that the effect to bone metabolism with medication may be able to be evaluated as reinforcement of the BMD recovery. We have so far investigated the Chinese herbal medicine based on Hachimi-jio-gan (HJG) which are more effective than HJG alone. In this study, we investigated the effects of our Chinese herbal prescription on BMD in the adenine-treated rats compared to that of vitamin D3treatment. Young male rats were administrated 100 mg/ml adenine for 8 weeks, and they showed renal failure and bone loss. The adenine-treated rats were divided into the following 3 groups, that is, the group experienced no treatment (control), the group givenour Chinese herbal medicine (HAO), and the group given vitamin D3 (VD3) medication. It is likely that VD3 medication was less effective for increase of the femoral BMD than increase of the spinal BMD. In contrast, HAO was effective for increase of the femoral BMD. The VD3 group showed low deoxypyridinoline (Dpd: bone resorption maker) as compared to the control group.However, the HAO group showed same or slightly high Dpd. It is suggested that VD3 may increase BMD by reduction of bone resorption, while HAO may show effect on BMD by activating bone metabolism. It is indicated that HAO may become a curative medicine for bone loss because of the different target site from vitamin D3.
基金supported by the National Science Fund for Distinguished Young Scholars of China(21825801)the National Natural Science Foundation of China(21972019)Fujian Outstanding Youth Fund(2019J06011)。
文摘Ru-based heterogeneous catalysts have been used in a wide range of important reactions.However,due to the sintering of Ru nanoparticles their practical applications are somewhat restricted.Herein,for the first time we report a new and facile strategy to confine Ru and/or Co nanoparticles(NPs) in the channels of N-doped carbon using benzoic acid to guide the deposition location of Ru.The developed catalyst with confined RuCo alloy particles exhibits high resistance against Ru sintering and displays excellent activity and long term stability for NH3 synthesis,achieving an NH3 synthesis rate of up to 18.9 mmol NH_(3) gcat^(-1)h^(-1)at 400℃,which is ca.2.25 times that of the catalyst prepared without confinement(with metal deposited on the support surface).In the latter case,there is an increase of nanoparticle size from 2.52 to 4.25 nm together with ca.48% decrease of NH_(3) synthesis rate after 68 h at 400℃.This study provides a new avenue for simple fabrication of precious-metal-based catalysts that are highly resistant against sintering,specifically suitable for low-temperature synthesis of ammonia with outstanding efficiency.
基金Project supported by the National Key R&D Program of China (2020YFB1505604)the National Natural Science Foundation of China(22178058,22078062)。
文摘Ammonia(NH_(3)) decomposition to release CO_x-free hydrogen(H_(2)) over non-noble catalysts has gained increasing attention.In this study,three nanostructured CeO_(2) with different morphologies,viz.rod(R).sphere(Sph),and spindle(Spi),were fabricated and served as supports for Ni/CeO_(2) catalyst.The CeO_(2)supports are different in particle sizes,specific surface area and porosity,resulting in the formation of Ni nanoparticles with distinguished sizes and dispersions.The surface properties of the Ni/CeO_(2) catalysts are not only distinct but also influential,affecting the adsorption and desorption of NH_(3),N_(2),and/or H_(2)molecules.The Ni/CeO_(2)-R catalyst shows superior catalytic activity compared to the other two,owing to its smaller Ni crystallite size and larger BET surface area.The most abundant strong basic sites are observed for Ni/CeO_(2)-Spi catalyst based on its exposed CeO_(2)(110) planes,which facilitates the donation of electrons to the Ni particles,benefiting the associative desorption of N atoms.Thus,Ni/CeO_(2)-Spi shows higher catalytic activity than Ni/CeO_(2)-Sph,despite their almost identical Ni crystallite sizes.
基金supported by the National Natural Science Foundation of China(Nos.22178061,21776047,21825801,and 21978051)。
文摘The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in the renewable energy.Generally,ZrO_(2) was regarded as an inferior support for Ru catalyst used in ammonia synthesis.Here we prepare ZrO_(2) with monoclinic phase and carbon species from ZrCl_(4) following the preparation route of UiO-66 as well as ammonia treatment.Owing to the presence of a larger amount of hydrogen adsorption as well as the easier desorption of hydrogen species,the ill effect of hydrogen species on the nitrogen adsorption-desorption and ammonia synthesis can be effectively alleviated.The resulting ZrO_(2)-supported Ru catalyst showed 4 times higher ammonia synthesis activity than the conventional Ru/ZrO_(2) obtained from zirconium nitrate.
基金supported by the National Key R&D Program of China(2021YFB4000400),the National Natural Science Foundation of China(21825801 and 21972019),Fujian Science and Technology Major Project(2020HZ07009),and the Talent Program of Fuzhou University(XRC-22036).
文摘Fossil fuels still dominate global energy structure in our modern society,and have led to massive CO_(2) emissions.Recently,ammonia has been regarded as a clean energy carrier toward diminishing or even eliminating the CO_(2) emissions and has received significant attention.The ammonia can be synthesized from atmospheric dinitrogen and green hydrogen from water electrolysis by renewable energies,and converted back into dinitrogen and water for energy release,as shown in Figure 1.Benefited from the matured ammonia manufacture and transportation throughout the world for over one century,the already existing high-capacity infrastructure helps efficient storage and redistribution of ammonia with lowest economic cost.However,although considerable progress has been made in this artificial nitrogen cycle,there are still many challenges in developing highly-efficient routes and catalysts.Herein,we evaluate the current catalytic routes of ammonia synthesis(including thermocatalytic synthesis,electrocatalytic synthesis and photocatalytic synthesis)and ammonia utilization(involving ammonia decomposition,direct ammonia fuel cells and ammonia combustion).We also discuss the key issue in each process,and anticipate that our viewpoints and opinions could facilitate the developments of artificial nitrogen cycle and energy decarbonization.
基金supported by the National Science Fund for Distinguished Young Scholars of China(21825801)the National Natural Science Foundation of China(21972019,21978051).
文摘To stabilize Ru nanoparticles against sintering is an urgent problem in the utilization of Ru-based catalysts for NH3 synthesis.In the present study,we used Ru-containing ZSM-5 as seeds to crystallize ZSM-5,and the resulted Ru@ZSM-5 catalyst is highly resistant against Ru sintering.According to the results of diffuse reflectance infrared fourier transform spectroscopy(DRIFTS)and transmission electron microscopy(TEM)analyses,the average size of Ru nanoparticles is around 3.6 nm,which is smaller than that of Ru/ZSM-5-IWI prepared by incipient wetness impregnation.In NH3 synthesis(N2:H2=1:3)at 400℃and 1 MPa,Ru@ZSM-5 displays a formation rate of 5.84 mmolNH3 gcat^-1 h^-1,which is much higher than that of Ru/ZSM-5-IWI(2.13 mmolNH3 gcat^-1 h^-1).According to the results of TEM,N2-temperatureprogrammed desorption(N2-TPD),X-ray photoelectron spectroscopy(XPS)and X-ray absorption fine structure(XAFS)studies,it is deduced that the superior performance of Ru@ZSM-5 is attributable to the small particle size and the ample existence of metallic Ru0 sites.This method of zeolite encapsulation is a feasible way to stabilize Ru nanoparticles for NH3 synthesis.
