Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocataly...Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocatalysts with excellent performance and low cost will facilitate the commercial use of these energy conversion technologies. Recently, dual-atom catalysts(DACs) have attracted considerable research interest since they exhibit higher metal atom loading and more flexible active sites compared to single-atom catalysts(SACs). In this paper, the latest preparation methods and characterization techniques of DACs are systematically reviewed. The advantages of homonuclear and heteronuclear DACs and the catalytic mechanism and identification technologies between the two DACs are highlighted. The current applications of DACs in the field of electrocatalysis are summarized. The development opportunities and challenges of DACs in the future are prospected. The ultimate goal is to provide new ideas for the preparation of new catalysts with excellent properties by customizing diatomic catalysts for electrochemical applications.展开更多
Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an oxidant.However,the cataly...Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an oxidant.However,the catalytic properties of ruthenium dimers have not yet been explored for visible light‐driven water oxidation.Herein,the photocatalytic performance of a dipyridyl propane‐bridged ruthenium dimer2was investigated in comparison with its monomeric precursor,[Ru(bda)(pic)2](1),in CH3CN/phosphate buffer mixed solvent in a three‐component system including a photosensitizer and a sacrificial electron acceptor.Experimental results showed that the activity of each catalyst was strongly dependent on the content of CH3CN in the phosphate buffer,which not only affected the driving force for water oxidation,but also altered the kinetics of the reaction,probably through different mechanisms associated with the O–O bond formation.As a result,dimer2showedsignificantly higher activity than monomer1in the solvent containing a low content of CH3CN,and comparable activities were attained with a high content of CH3CN in the solvent.Under the optimal conditions,complex2achieved a turnover number of638for photocatalytic O2evolution.展开更多
The reduction of an aqueous solution of sodium molybdate by iron powder at low pH value (～0.83), in the presence of ethylenediaminetetraacetate (EDTA) ligand, gives the title compound [Fe(H 2O) 6][Mo 2O 4(EDTA)]·...The reduction of an aqueous solution of sodium molybdate by iron powder at low pH value (～0.83), in the presence of ethylenediaminetetraacetate (EDTA) ligand, gives the title compound [Fe(H 2O) 6][Mo 2O 4(EDTA)]·5H 2O 1, which was characterized by elemental analysis, IR and X ray single crystal diffraction techniques. Compound 1 crystallizes in monoclinic system, space group P2 1/c, C 10 H 34 N 2FeMo 2O 23 , M r=798.12, a=8.781(1), b=14.081(1), c=21.353(1) , β= 92\^688(1)°, V = 2637.2(3) 3, Z = 4, D c = 2.010 g·cm -3 , μ = 1.579 mm -1 , F (000)=1608, the final R =0.0530 and wR =0.1271 for 3312 observed reflections. The binuclear oxomolybdenum(V) anion and the six coordinated Fe(II) cation are linked to infinite three dimensional network through several hydrogen bonds towards different directions between crystal waters, Fe(II) cation and Mo(V) anion.展开更多
Photocatalytic reduction of CO2 to CO is a promising approach for storing solar energy in chemicals and mitigating the greenhouse effect of CO2.Our recent studies revealed that[(μ-bdt)Fe2(CO)6](1,bdt=benzene-1,2-dith...Photocatalytic reduction of CO2 to CO is a promising approach for storing solar energy in chemicals and mitigating the greenhouse effect of CO2.Our recent studies revealed that[(μ-bdt)Fe2(CO)6](1,bdt=benzene-1,2-dithiolato),a[FeFe]-hydrogenase model with a rigid and conjugate S-to-S bridge,was catalytically active for the selective photochemical reduction of CO2 to CO,while its analogous complex[(μ-edt)Fe2(CO)6](2,edt=ethane-1,2-dithiolato)was inactive.In this study,it was found that the turnover number of 1 for CO evolution reached 710 for the 1/[Ru(bpy)3]2+/BIH(BIH=1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]-imidazole)system under optimal conditions over 4.5 h of visible-light irradiation,with a turnover frequency of 7.12 min−1 in the first hour,a high selectivity of 97%for CO,and an internal quantum yield of 2.8%.Interestingly,the catalytic selectivity of 1 can be adjusted and even completely switched in a facile manner between the photochemical reductions of CO2 to CO and of protons to H2 simply by adding different amounts of triethanolamine to the catalytic system.The electron transfer in the photocatalytic system was studied by steady-state fluorescence and transient absorption spectroscopy,and a plausible mechanism for the photocatalytic reaction was proposed.展开更多
Novel hydrophilic NaYF4:Yb^3+,Tm^3+@NaGdF4:Ce^3+,Eu^3+double-jacket microtubes(DJMTs)with upconversion/downconversion dual-mode luminescence were designed and prepared through epitaxial growth of NaGdF4:Ce^3+,Eu^3+she...Novel hydrophilic NaYF4:Yb^3+,Tm^3+@NaGdF4:Ce^3+,Eu^3+double-jacket microtubes(DJMTs)with upconversion/downconversion dual-mode luminescence were designed and prepared through epitaxial growth of NaGdF4:Ce^3+,Eu^3+shell onto the NaYF4:Yb^3+,Tm^3+microtube via poly(acrylic acid)(PAA)mediated hydrothermal method.It is demonstrated that PAA ligand played an important role in guiding the direct growth of NaGdF4:Ce^3+,Eu^3+shell onto the surface of NaYF4:Yb^3+,Tm^3+parent microtubes.The growth of NaGdF4:Ce^3+,Eu^3+shell experienced a crystal phase transition fromβ-NaGdF4 andβ-NaYF4 mixture toβ-NaYF4@NaGdF4 composite crystal,and morphology evolution from mixture ofβ-NaGdF4:Ce^3+,Eu^3+nanorods andβ-NaYF4:Yb^3+,Tm^3+microtubes to NaYF4:Yb^3+,Tm^3+@NaGdF4:Ce^3+,Eu^3+DJMTs.The formation mechanism of DJMTs was the dissolution−renucleation ofβ-NaGdF4:Ce^3+,Eu^3+nanorods and the growth ofβ-NaGdF4:Ce^3+,Eu^3+shell via the classical Ostwald ripening mechanism.The as-prepared DJMTs could exhibit blue upconversion and red downconversion luminescence,which was further made into environmentally benign luminescent inks for creating highly secured and fluorescent-based anti-counterfeiting patterns via inkjet printing.展开更多
The complex [Rh（CO）（Pz）（TPPMS）]2, （TPPMS = m-sulfonatophenyl-diphenylphosphine, Pz = Pirazolate） was evaluated as a catalyst precursor in the hydroformylation of allylbenzenes （eugenol and estragol） and terp...The complex [Rh（CO）（Pz）（TPPMS）]2, （TPPMS = m-sulfonatophenyl-diphenylphosphine, Pz = Pirazolate） was evaluated as a catalyst precursor in the hydroformylation of allylbenzenes （eugenol and estragol） and terpenes （limonene and myrcene） and in the hydrogenation of α,β-unsaturated aldehydes （crotonaldehyde, cinnamaldehyde and citral） in a biphasic medium toluene/ionic liquid. Under the reaction conditions studied （P = 600 psi, T= 95 ℃, S/C = 300：1）, the rhodium system showed a high activity and selectivity towards the desired aldehydes. The catalytic phase could be recycled up to five times without any evident loss of activity or selectivity.展开更多
Non-convex methods play a critical role in low-rank tensor completion for their approximation to tensor rank is tighter than that of convex methods.But they usually cost much more time for calculating singular values ...Non-convex methods play a critical role in low-rank tensor completion for their approximation to tensor rank is tighter than that of convex methods.But they usually cost much more time for calculating singular values of large tensors.In this paper,we propose a double transformed tubal nuclear norm(DTTNN)to replace the rank norm penalty in low rank tensor completion(LRTC)tasks.DTTNN turns the original non-convex penalty of a large tensor into two convex penalties of much smaller tensors,and it is shown to be an equivalent transformation.Therefore,DTTNN could take advantage of non-convex envelopes while saving time.Experimental results on color image and video inpainting tasks verify the effectiveness of DTTNN compared with state-of-the-art methods.展开更多
The title compound [Zn(Him2Py)(N3)2]2 (Zn2C26H38N18O2, Mr = 765.48) has been prepared and structurally characterized by X-ray diffraction methods. It crystallizes in monoclinic, space group P21/n with a = 10.989(3), b...The title compound [Zn(Him2Py)(N3)2]2 (Zn2C26H38N18O2, Mr = 765.48) has been prepared and structurally characterized by X-ray diffraction methods. It crystallizes in monoclinic, space group P21/n with a = 10.989(3), b = 11.519(3), c = 13.812(4) ? b = 101.700(5), V = 1711.9(9) ?, Z = 2, Dc = 1.485 g/cm3, m(MoKa) = 1.456 mm～1, F(000) = 792, the final R = 0.0401 and wR = 0.0861 for 2054 observed reflections with I>2s(I). The imino nitroxide 2-(3- methyl-2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl (im2Py) was reduced to obtain 2-(3-methyl -2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-ydroxy (Him2Py) coordinating to the zinc (II) ion, around which the coordination geometry is a square-based pyramid with a terminal nitrogen atom located at the apical position. The four basal sites are occupied by two m1,1 nitrogen atoms from two different bridging azide ions and two nitrogen atoms from Him2Py. The units of [Zn(Him2Py)(N3)2]2 were connected as two dimension planes by intermolecular hydrogen bonds.展开更多
文摘Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocatalysts with excellent performance and low cost will facilitate the commercial use of these energy conversion technologies. Recently, dual-atom catalysts(DACs) have attracted considerable research interest since they exhibit higher metal atom loading and more flexible active sites compared to single-atom catalysts(SACs). In this paper, the latest preparation methods and characterization techniques of DACs are systematically reviewed. The advantages of homonuclear and heteronuclear DACs and the catalytic mechanism and identification technologies between the two DACs are highlighted. The current applications of DACs in the field of electrocatalysis are summarized. The development opportunities and challenges of DACs in the future are prospected. The ultimate goal is to provide new ideas for the preparation of new catalysts with excellent properties by customizing diatomic catalysts for electrochemical applications.
基金supported by the National Basic Research Program of China (973 Program, 2014CB239402)the National Natural Science Foundation of China (21476043)+1 种基金the Fundamental Research Funds for the Central Universities (DUT17ZD204)the Swedish Energy Agency and K&A Wallenberg Foundation~~
文摘Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an oxidant.However,the catalytic properties of ruthenium dimers have not yet been explored for visible light‐driven water oxidation.Herein,the photocatalytic performance of a dipyridyl propane‐bridged ruthenium dimer2was investigated in comparison with its monomeric precursor,[Ru(bda)(pic)2](1),in CH3CN/phosphate buffer mixed solvent in a three‐component system including a photosensitizer and a sacrificial electron acceptor.Experimental results showed that the activity of each catalyst was strongly dependent on the content of CH3CN in the phosphate buffer,which not only affected the driving force for water oxidation,but also altered the kinetics of the reaction,probably through different mechanisms associated with the O–O bond formation.As a result,dimer2showedsignificantly higher activity than monomer1in the solvent containing a low content of CH3CN,and comparable activities were attained with a high content of CH3CN in the solvent.Under the optimal conditions,complex2achieved a turnover number of638for photocatalytic O2evolution.
文摘The reduction of an aqueous solution of sodium molybdate by iron powder at low pH value (～0.83), in the presence of ethylenediaminetetraacetate (EDTA) ligand, gives the title compound [Fe(H 2O) 6][Mo 2O 4(EDTA)]·5H 2O 1, which was characterized by elemental analysis, IR and X ray single crystal diffraction techniques. Compound 1 crystallizes in monoclinic system, space group P2 1/c, C 10 H 34 N 2FeMo 2O 23 , M r=798.12, a=8.781(1), b=14.081(1), c=21.353(1) , β= 92\^688(1)°, V = 2637.2(3) 3, Z = 4, D c = 2.010 g·cm -3 , μ = 1.579 mm -1 , F (000)=1608, the final R =0.0530 and wR =0.1271 for 3312 observed reflections. The binuclear oxomolybdenum(V) anion and the six coordinated Fe(II) cation are linked to infinite three dimensional network through several hydrogen bonds towards different directions between crystal waters, Fe(II) cation and Mo(V) anion.
文摘Photocatalytic reduction of CO2 to CO is a promising approach for storing solar energy in chemicals and mitigating the greenhouse effect of CO2.Our recent studies revealed that[(μ-bdt)Fe2(CO)6](1,bdt=benzene-1,2-dithiolato),a[FeFe]-hydrogenase model with a rigid and conjugate S-to-S bridge,was catalytically active for the selective photochemical reduction of CO2 to CO,while its analogous complex[(μ-edt)Fe2(CO)6](2,edt=ethane-1,2-dithiolato)was inactive.In this study,it was found that the turnover number of 1 for CO evolution reached 710 for the 1/[Ru(bpy)3]2+/BIH(BIH=1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]-imidazole)system under optimal conditions over 4.5 h of visible-light irradiation,with a turnover frequency of 7.12 min−1 in the first hour,a high selectivity of 97%for CO,and an internal quantum yield of 2.8%.Interestingly,the catalytic selectivity of 1 can be adjusted and even completely switched in a facile manner between the photochemical reductions of CO2 to CO and of protons to H2 simply by adding different amounts of triethanolamine to the catalytic system.The electron transfer in the photocatalytic system was studied by steady-state fluorescence and transient absorption spectroscopy,and a plausible mechanism for the photocatalytic reaction was proposed.
基金Project(51874129)supported by the National Natural Science Foundation of ChinaProjects(2018JJ3115,2019JJ60049)supported by the Science Foundation of Hunan Province,ChinaProjects(19B153,19B158)supported by the Scientific Research Fund of Hunan Provincial Education Department,China。
文摘Novel hydrophilic NaYF4:Yb^3+,Tm^3+@NaGdF4:Ce^3+,Eu^3+double-jacket microtubes(DJMTs)with upconversion/downconversion dual-mode luminescence were designed and prepared through epitaxial growth of NaGdF4:Ce^3+,Eu^3+shell onto the NaYF4:Yb^3+,Tm^3+microtube via poly(acrylic acid)(PAA)mediated hydrothermal method.It is demonstrated that PAA ligand played an important role in guiding the direct growth of NaGdF4:Ce^3+,Eu^3+shell onto the surface of NaYF4:Yb^3+,Tm^3+parent microtubes.The growth of NaGdF4:Ce^3+,Eu^3+shell experienced a crystal phase transition fromβ-NaGdF4 andβ-NaYF4 mixture toβ-NaYF4@NaGdF4 composite crystal,and morphology evolution from mixture ofβ-NaGdF4:Ce^3+,Eu^3+nanorods andβ-NaYF4:Yb^3+,Tm^3+microtubes to NaYF4:Yb^3+,Tm^3+@NaGdF4:Ce^3+,Eu^3+DJMTs.The formation mechanism of DJMTs was the dissolution−renucleation ofβ-NaGdF4:Ce^3+,Eu^3+nanorods and the growth ofβ-NaGdF4:Ce^3+,Eu^3+shell via the classical Ostwald ripening mechanism.The as-prepared DJMTs could exhibit blue upconversion and red downconversion luminescence,which was further made into environmentally benign luminescent inks for creating highly secured and fluorescent-based anti-counterfeiting patterns via inkjet printing.
文摘The complex [Rh（CO）（Pz）（TPPMS）]2, （TPPMS = m-sulfonatophenyl-diphenylphosphine, Pz = Pirazolate） was evaluated as a catalyst precursor in the hydroformylation of allylbenzenes （eugenol and estragol） and terpenes （limonene and myrcene） and in the hydrogenation of α,β-unsaturated aldehydes （crotonaldehyde, cinnamaldehyde and citral） in a biphasic medium toluene/ionic liquid. Under the reaction conditions studied （P = 600 psi, T= 95 ℃, S/C = 300：1）, the rhodium system showed a high activity and selectivity towards the desired aldehydes. The catalytic phase could be recycled up to five times without any evident loss of activity or selectivity.
基金financially supported by the National Nautral Science Foundation of China(No.61703206)
文摘Non-convex methods play a critical role in low-rank tensor completion for their approximation to tensor rank is tighter than that of convex methods.But they usually cost much more time for calculating singular values of large tensors.In this paper,we propose a double transformed tubal nuclear norm(DTTNN)to replace the rank norm penalty in low rank tensor completion(LRTC)tasks.DTTNN turns the original non-convex penalty of a large tensor into two convex penalties of much smaller tensors,and it is shown to be an equivalent transformation.Therefore,DTTNN could take advantage of non-convex envelopes while saving time.Experimental results on color image and video inpainting tasks verify the effectiveness of DTTNN compared with state-of-the-art methods.
基金This work was supported by the National Natural Science Foundation of China (No. 20171025 and No. 90101028)
文摘The title compound [Zn(Him2Py)(N3)2]2 (Zn2C26H38N18O2, Mr = 765.48) has been prepared and structurally characterized by X-ray diffraction methods. It crystallizes in monoclinic, space group P21/n with a = 10.989(3), b = 11.519(3), c = 13.812(4) ? b = 101.700(5), V = 1711.9(9) ?, Z = 2, Dc = 1.485 g/cm3, m(MoKa) = 1.456 mm～1, F(000) = 792, the final R = 0.0401 and wR = 0.0861 for 2054 observed reflections with I>2s(I). The imino nitroxide 2-(3- methyl-2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl (im2Py) was reduced to obtain 2-(3-methyl -2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-ydroxy (Him2Py) coordinating to the zinc (II) ion, around which the coordination geometry is a square-based pyramid with a terminal nitrogen atom located at the apical position. The four basal sites are occupied by two m1,1 nitrogen atoms from two different bridging azide ions and two nitrogen atoms from Him2Py. The units of [Zn(Him2Py)(N3)2]2 were connected as two dimension planes by intermolecular hydrogen bonds.
