Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approa...Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approach to engineering the coordination environment of M-N-C(M=Fe,Co,and Ni)SACs by using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator.Compared with that in N2,NH3 was able to promote the doping of N at 7<700℃yet etch the N-species at higher temperatures,by which the M-N coordination number(CN)and the electronic structure were delicately tuned.It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN.As a consequence,the capability of Ni-N-C to dissociate H2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved.Moreover,this modulation method could be applied to other transition metals including Fe and Co.In particular,the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h~1 with 99%selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene,which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts,demonstrating the great potential of engineering the coordination environment of SACs.展开更多
Combination of CO_(2) capture using inorganic alkali with subsequently electrochemical conversion of the resultant HCO_(3)^(-)to high-value chemicals is a promising route of low cost and high efficiency.The electroche...Combination of CO_(2) capture using inorganic alkali with subsequently electrochemical conversion of the resultant HCO_(3)^(-)to high-value chemicals is a promising route of low cost and high efficiency.The electrochemical reduction of HCO_(3)^(-)is challenging due to the inaccessible of negatively charged molecular groups to the electrode surface.Herein,we adopt a comprehensive strategy to tackle this challenge,i.e.,cascade of in situ chemical conversion of HCO_(3)^(-)to CO_(2) and CO_(2) electrochemical reduction in a flow cell.With a tailored Ni-N-S single atom catalyst(SACs),where sulfur(S)atoms located in the second shell of Ni center,the CO_(2)electroreduction(CO_(2)ER)to CO is boosted.The experimental results and density functional theory(DFT)calculations reveal that the introduction of S increases the p electron density of N atoms near Ni atom,thereby stabilizing^(*)H over N and boosting the first proton coupled electron transfer process of CO_(2)ER,i.e.,^(*)+e^(-)+^(*)H+^(*)CO_(2)→^(*)COOH.As a result,the obtained catalyst exhibits a high faradaic efficiency(FE_(CO)~98%)and a low overpotential of 425 mV for CO production as well as a superior turnover frequency(TOF)of 47397 h^(-1),outcompeting most of the reported Ni SACs.More importantly,an extremely high FECOof 90%is achieved at 50 mA cm^(-2)in the designed membrane electrode assembly(MEA)cascade electrolyzer fed with liquid bicarbonate.This work not only highlights the significant role of the second coordination on the first coordination shell of the central metal for CO_(2)ER,but also provides an alternative and feasible strategy to realize the electrochemical conversion of HCO_(3)^(-)to high-value chemicals.展开更多
Although precious transition metals such as palladium,platinum,and iridium are widely used in hydrogenation reactions,the earth-abundant transition metal-catalyzed highly selective semi-hydrogenation of terminal alkyn...Although precious transition metals such as palladium,platinum,and iridium are widely used in hydrogenation reactions,the earth-abundant transition metal-catalyzed highly selective semi-hydrogenation of terminal alkynes to terminal alkenes remains poorly developed and a challenge.Herein we demonstrate the excellent selective,cost-effective semi-hydrogenation of terminal alkynes via a novel graphene encapsulated Ni@N/C catalyst.The graphene layer encapsulated nano-catalyst Ni@N/C could significantly avoid metal leaching and improve the stability of the catalyst.The strong interaction of nitrogen with the Ni nanoparticles regulates the activity of Ni towards selective semi-hydrogenation of terminal alkynes.Substrates having un-functionalized as well as functionalized substituents,and substrates having sensitive functional groups(olefins,ketones)which pose a challenge to hydrogenate,were semi-hydrogenated with excellent conversion(up to 99%)and selectivity(up to 99%)under optimized reaction conditions.展开更多
将二氧化碳转化为高附加值的燃料和化学品是缓解当前能源危机和控制温室气体排放的有效策略之一,但此法受限于缺乏高活性与高选择性的电催化剂。因此,我们通过热解含镍金属有机框架结构(MOF)和二氰二胺制得负载高含量镍单原子(7.77%(w)...将二氧化碳转化为高附加值的燃料和化学品是缓解当前能源危机和控制温室气体排放的有效策略之一,但此法受限于缺乏高活性与高选择性的电催化剂。因此,我们通过热解含镍金属有机框架结构(MOF)和二氰二胺制得负载高含量镍单原子(7.77%(w))的超薄氮掺杂二维碳纳米片用于电催化还原CO_(2)生成CO。研究发现高温热解能将MOF中Ni^(2+)转化为Ni^(+)-N-C和Ni^(2+)-N-C结构,且Ni^(+)-N-C含量依赖于热解温度——其含量随热解温度增加呈现火山型变化。800℃下,Ni^(2+)到Ni^(+)-N-C的转化和石墨化的C生成达到最优水平。Ni^(+)-N-C结构有适宜的^(*)CO中间体结合能,能有效地抑制析氢反应的同时还能促进CO生成。因此,800℃热处理制得的材料(Ni-N-C-800)催化CO_(2)生成CO效率最高。调节电解液浓度,能进一步优化电催化性能。当电解液(碳酸氢钾)浓度为0.5 mol·L^(−1)时,Ni-N-C-800的CO生成选择性在较宽电压窗口内(−0.77到^(−1).07 V vs.RHE)都高于90%,且具有优良的稳定性。这些结果表明,选择合适的前躯体通过调控热解温度以及氮掺杂可以有效提高镍基MOF衍生催化剂的二氧化碳电催化性能。展开更多
基金supported by the National Key Technology R&D Program of China(No.2020YFA0710202)the National Natural Science Foundation of China(Nos.U1662130,21690080,21690084,and 21721004)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17020100)。
文摘Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approach to engineering the coordination environment of M-N-C(M=Fe,Co,and Ni)SACs by using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator.Compared with that in N2,NH3 was able to promote the doping of N at 7<700℃yet etch the N-species at higher temperatures,by which the M-N coordination number(CN)and the electronic structure were delicately tuned.It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN.As a consequence,the capability of Ni-N-C to dissociate H2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved.Moreover,this modulation method could be applied to other transition metals including Fe and Co.In particular,the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h~1 with 99%selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene,which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts,demonstrating the great potential of engineering the coordination environment of SACs.
基金financially supported by the Natural Science Foundation of Shandong Province (ZR2020QB132,ZR2020MB025)the Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure (SKL202108SIC)the Taishan Scholar Program of Shandong Province (ts201712046)。
文摘Combination of CO_(2) capture using inorganic alkali with subsequently electrochemical conversion of the resultant HCO_(3)^(-)to high-value chemicals is a promising route of low cost and high efficiency.The electrochemical reduction of HCO_(3)^(-)is challenging due to the inaccessible of negatively charged molecular groups to the electrode surface.Herein,we adopt a comprehensive strategy to tackle this challenge,i.e.,cascade of in situ chemical conversion of HCO_(3)^(-)to CO_(2) and CO_(2) electrochemical reduction in a flow cell.With a tailored Ni-N-S single atom catalyst(SACs),where sulfur(S)atoms located in the second shell of Ni center,the CO_(2)electroreduction(CO_(2)ER)to CO is boosted.The experimental results and density functional theory(DFT)calculations reveal that the introduction of S increases the p electron density of N atoms near Ni atom,thereby stabilizing^(*)H over N and boosting the first proton coupled electron transfer process of CO_(2)ER,i.e.,^(*)+e^(-)+^(*)H+^(*)CO_(2)→^(*)COOH.As a result,the obtained catalyst exhibits a high faradaic efficiency(FE_(CO)~98%)and a low overpotential of 425 mV for CO production as well as a superior turnover frequency(TOF)of 47397 h^(-1),outcompeting most of the reported Ni SACs.More importantly,an extremely high FECOof 90%is achieved at 50 mA cm^(-2)in the designed membrane electrode assembly(MEA)cascade electrolyzer fed with liquid bicarbonate.This work not only highlights the significant role of the second coordination on the first coordination shell of the central metal for CO_(2)ER,but also provides an alternative and feasible strategy to realize the electrochemical conversion of HCO_(3)^(-)to high-value chemicals.
基金supported financially by the National Natural Science Foundation of China(Project 51976225).
文摘Although precious transition metals such as palladium,platinum,and iridium are widely used in hydrogenation reactions,the earth-abundant transition metal-catalyzed highly selective semi-hydrogenation of terminal alkynes to terminal alkenes remains poorly developed and a challenge.Herein we demonstrate the excellent selective,cost-effective semi-hydrogenation of terminal alkynes via a novel graphene encapsulated Ni@N/C catalyst.The graphene layer encapsulated nano-catalyst Ni@N/C could significantly avoid metal leaching and improve the stability of the catalyst.The strong interaction of nitrogen with the Ni nanoparticles regulates the activity of Ni towards selective semi-hydrogenation of terminal alkynes.Substrates having un-functionalized as well as functionalized substituents,and substrates having sensitive functional groups(olefins,ketones)which pose a challenge to hydrogenate,were semi-hydrogenated with excellent conversion(up to 99%)and selectivity(up to 99%)under optimized reaction conditions.
文摘将二氧化碳转化为高附加值的燃料和化学品是缓解当前能源危机和控制温室气体排放的有效策略之一,但此法受限于缺乏高活性与高选择性的电催化剂。因此,我们通过热解含镍金属有机框架结构(MOF)和二氰二胺制得负载高含量镍单原子(7.77%(w))的超薄氮掺杂二维碳纳米片用于电催化还原CO_(2)生成CO。研究发现高温热解能将MOF中Ni^(2+)转化为Ni^(+)-N-C和Ni^(2+)-N-C结构,且Ni^(+)-N-C含量依赖于热解温度——其含量随热解温度增加呈现火山型变化。800℃下,Ni^(2+)到Ni^(+)-N-C的转化和石墨化的C生成达到最优水平。Ni^(+)-N-C结构有适宜的^(*)CO中间体结合能,能有效地抑制析氢反应的同时还能促进CO生成。因此,800℃热处理制得的材料(Ni-N-C-800)催化CO_(2)生成CO效率最高。调节电解液浓度,能进一步优化电催化性能。当电解液(碳酸氢钾)浓度为0.5 mol·L^(−1)时,Ni-N-C-800的CO生成选择性在较宽电压窗口内(−0.77到^(−1).07 V vs.RHE)都高于90%,且具有优良的稳定性。这些结果表明,选择合适的前躯体通过调控热解温度以及氮掺杂可以有效提高镍基MOF衍生催化剂的二氧化碳电催化性能。
