Carbon nanofibers with hollow structures have an excellent application prospect in various fields be-cause of their high specific surface area and abundant active sites.PAN-based hollow carbon nanofiber doped with Co/...Carbon nanofibers with hollow structures have an excellent application prospect in various fields be-cause of their high specific surface area and abundant active sites.PAN-based hollow carbon nanofiber doped with Co/CoO(H-Co/CoO-CNF)was successfully prepared and used as a catalyst to activate perox-ymonosulfate(PMS)and degrade Rhodamine B(RhB).The catalyst showed a surprising degradation rate(98.89%)of RhB within 15 min and had good degradation performance in a wide pH range(pH 1.5-11.2).Compared with solid fibers,H-Co/CoO-CNF shows better cyclic characteristics.The catalyst is also mag-netic and recoverable easily due to the addition of Co/CoO.Two pathways of both radical(SO_(4)·^(−))and non-radical(^(1)O_(2))exist during the RhB degradation process are confirmed through electron paramagnetic resonance(EPR)analysis and radical quenching experiments.This work provides a new idea for hollow fibers loaded with metals and their oxides and can guide the development of catalysts for advanced oxi-dation processes in the future.展开更多
Development of cost-effective and highly-efficient bifunctional hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts is crucial for overall water splitting in practical utilization.Herein,we pro...Development of cost-effective and highly-efficient bifunctional hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts is crucial for overall water splitting in practical utilization.Herein,we proposed a novel non-noble metal bifunctional,HER/OER electrocatalyst by synergistically coupling a dual-active Co-based heterojunction(Co-CoO)with high conductive and stable two-dimensional Ti_(3)C_(2)-MXene(defined as Co-CoO/Ti^(3)CrMXene).A series of characterizations and theoretical calculations'verify that the synergistic effect of metallic Co with HER activity and Coo with OER performance leads to superb bifunctional catalytic performance,and Ti_(3)C_(2)-MXene can enhance electrical conductivity and prevent the aggregation of the Co-based catalysts,thereby improving both the activity arid stability.Co-Co0/Ti_(3)C_(2)-MXene presents low onset potential(11onse1)of 8 mV and,Tafel slope of 47 mV·dec^(-1) for HER(close to that of Pt/C)and 17onset of 196 mV and Tafel slope of 47 mV·dec^(-1) for OER(superior to:that of Ru02).Assembled as an electrolyzer,Co-CoO/Ti_(3)C_(2)-MXene shows a low voltage of 1.55 V at 10 mA·cm^(-2),high Faradaic efficiency and remarkable stability.It can be driven by a solar cell of-1.55 V for consecutive production of hydrogen and oxygen gases.展开更多
The depolymerization and upgrading of lignin from raw biomass,while keeping cellulose intact is important in biorefinery and various metal-based catalysts have been used in reductive catalytic fractionation,a key meth...The depolymerization and upgrading of lignin from raw biomass,while keeping cellulose intact is important in biorefinery and various metal-based catalysts have been used in reductive catalytic fractionation,a key method in"lignin-first"strategy,Recently,we found that a core-shell structured Co@CoO catalyst with CoO shell as the real active site had excellent performance in the hydrogenolysis of 5-hydromethylfurfural to 2,5-dimethylfuran due to its unique ability to dissociate H_(2)and yield active H^(δ-)species(Xiang et al.,2022).In this work,we report a one-pot depolymerization and upgrading of lignocellulose to alkylcyclohexanols,a flavour precursor,with intact cellulose over this unique core-shell structured catalyst,Co@CoO.Lignin model compounds(β-O-4,4-O-5,α-O-4)were first used to clarify the activity of Co@CoO catalyst.Then,the one-pot conversion of various organosolv lignin(birch,pine and poplar)to alkylcyclohexanols was realized with the mass yield of alkylcyclohexanols up to25.8 wt%from birch lignin under the reaction condition of 210℃,1 MPa H_(2),16 h.Finally,the corresponding woody sawdusts were used as feedstocks and found that the Co@CoO catalyst indeed preferentially depolymerized and upgraded the lignin part and obtained the same alkylcyclohexanols products with the retention of cellulose-rich pulp.The collected alkylcyclohexanols were further esterified to obtain valueadded esters,which can be used as flavors.This work will inspire the design of new efficient metal oxide catalysts in lignin fractionation and depolymerization to high-value-added chemicals with intact cellulose.展开更多
In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were...In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were uniformly dispersed on the rhombus N-doped carbon(NC)nanoflakes.Transmission electron microscopic,X-ray diffraction spectrometric,and X-ray photoelectron spectroscopic analyses revealed the coexistence of metallic Co and Co oxides nanoparticles.It was found that Co/CoO_(x)@NC obtained at 500℃ annealing temperature exhibited the highest electrocatalytic OER activity,with 307 and375 m V overpotential to achieve 10 and 100 m A cm^(-2) current densities.Besides,thanks to the in-situ annealing process,Co/CoO_(x)@NC showed excellent catalytic stability with 97.4%current density retention after 24 h electrolysis at 1.66 V vs.RHE electrode potential.Further investigations revealed that the ultrasmall Co/Co Oxnanoparticles distributed on N-doped carbon template contribute significantly towards OER electrocatalysis through enlarging the activity surface areas and enhancing the intrinsic electrochemical activity due to the presence of metallic Co.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52072193)the Shandong Provin-cial Natural Science Foundation(Nos.ZR2021JQ16,ZR2019YQ19 and ZR2019BEM018)+2 种基金the Project of Shandong Province Higher Ed-ucational Science and Technology Program(No.2019KJA026)the Shandong Provincial College Students’Innovative Entrepreneurial Training(Nos.S202111065214 andS202211065062)State Key Laboratory for Modification of Chemical Fibers and Polymer Mate-rials(No.KF2217).
文摘Carbon nanofibers with hollow structures have an excellent application prospect in various fields be-cause of their high specific surface area and abundant active sites.PAN-based hollow carbon nanofiber doped with Co/CoO(H-Co/CoO-CNF)was successfully prepared and used as a catalyst to activate perox-ymonosulfate(PMS)and degrade Rhodamine B(RhB).The catalyst showed a surprising degradation rate(98.89%)of RhB within 15 min and had good degradation performance in a wide pH range(pH 1.5-11.2).Compared with solid fibers,H-Co/CoO-CNF shows better cyclic characteristics.The catalyst is also mag-netic and recoverable easily due to the addition of Co/CoO.Two pathways of both radical(SO_(4)·^(−))and non-radical(^(1)O_(2))exist during the RhB degradation process are confirmed through electron paramagnetic resonance(EPR)analysis and radical quenching experiments.This work provides a new idea for hollow fibers loaded with metals and their oxides and can guide the development of catalysts for advanced oxi-dation processes in the future.
基金supported by the National Key R&D Program of China(No.2018YFB1502401)the National Natural Science Foundation of China(Nos.21631004,21805073,U20A20250,and 21901064)+3 种基金the Natural Science Foundation of Heilongjiang Province(No.QC2018014)the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(Nos.UNPYSCT-2017123 and UNPYSCT-2017124)the Basic Research fund of Heilongjiang University in Heilongjiang Province(No.RCYJTD201801)Heilongjiang University Excellent Youth Foundation.
文摘Development of cost-effective and highly-efficient bifunctional hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts is crucial for overall water splitting in practical utilization.Herein,we proposed a novel non-noble metal bifunctional,HER/OER electrocatalyst by synergistically coupling a dual-active Co-based heterojunction(Co-CoO)with high conductive and stable two-dimensional Ti_(3)C_(2)-MXene(defined as Co-CoO/Ti^(3)CrMXene).A series of characterizations and theoretical calculations'verify that the synergistic effect of metallic Co with HER activity and Coo with OER performance leads to superb bifunctional catalytic performance,and Ti_(3)C_(2)-MXene can enhance electrical conductivity and prevent the aggregation of the Co-based catalysts,thereby improving both the activity arid stability.Co-Co0/Ti_(3)C_(2)-MXene presents low onset potential(11onse1)of 8 mV and,Tafel slope of 47 mV·dec^(-1) for HER(close to that of Pt/C)and 17onset of 196 mV and Tafel slope of 47 mV·dec^(-1) for OER(superior to:that of Ru02).Assembled as an electrolyzer,Co-CoO/Ti_(3)C_(2)-MXene shows a low voltage of 1.55 V at 10 mA·cm^(-2),high Faradaic efficiency and remarkable stability.It can be driven by a solar cell of-1.55 V for consecutive production of hydrogen and oxygen gases.
基金supported financially by the National Natural Science Foundation of China(Nos.21832002,21808063,22002043,21872050)。
文摘The depolymerization and upgrading of lignin from raw biomass,while keeping cellulose intact is important in biorefinery and various metal-based catalysts have been used in reductive catalytic fractionation,a key method in"lignin-first"strategy,Recently,we found that a core-shell structured Co@CoO catalyst with CoO shell as the real active site had excellent performance in the hydrogenolysis of 5-hydromethylfurfural to 2,5-dimethylfuran due to its unique ability to dissociate H_(2)and yield active H^(δ-)species(Xiang et al.,2022).In this work,we report a one-pot depolymerization and upgrading of lignocellulose to alkylcyclohexanols,a flavour precursor,with intact cellulose over this unique core-shell structured catalyst,Co@CoO.Lignin model compounds(β-O-4,4-O-5,α-O-4)were first used to clarify the activity of Co@CoO catalyst.Then,the one-pot conversion of various organosolv lignin(birch,pine and poplar)to alkylcyclohexanols was realized with the mass yield of alkylcyclohexanols up to25.8 wt%from birch lignin under the reaction condition of 210℃,1 MPa H_(2),16 h.Finally,the corresponding woody sawdusts were used as feedstocks and found that the Co@CoO catalyst indeed preferentially depolymerized and upgraded the lignin part and obtained the same alkylcyclohexanols products with the retention of cellulose-rich pulp.The collected alkylcyclohexanols were further esterified to obtain valueadded esters,which can be used as flavors.This work will inspire the design of new efficient metal oxide catalysts in lignin fractionation and depolymerization to high-value-added chemicals with intact cellulose.
基金partially supported by the National Natural Science Foundation of China(No.21805308)the Taishan Scholar Project of Shandong province,the Key Research and Development Program of Shandong Province(No.2019GSF109075)the Fundamental Research Funds for the Central Universities(No.18CX06065A,No.19CX05001A)。
文摘In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were uniformly dispersed on the rhombus N-doped carbon(NC)nanoflakes.Transmission electron microscopic,X-ray diffraction spectrometric,and X-ray photoelectron spectroscopic analyses revealed the coexistence of metallic Co and Co oxides nanoparticles.It was found that Co/CoO_(x)@NC obtained at 500℃ annealing temperature exhibited the highest electrocatalytic OER activity,with 307 and375 m V overpotential to achieve 10 and 100 m A cm^(-2) current densities.Besides,thanks to the in-situ annealing process,Co/CoO_(x)@NC showed excellent catalytic stability with 97.4%current density retention after 24 h electrolysis at 1.66 V vs.RHE electrode potential.Further investigations revealed that the ultrasmall Co/Co Oxnanoparticles distributed on N-doped carbon template contribute significantly towards OER electrocatalysis through enlarging the activity surface areas and enhancing the intrinsic electrochemical activity due to the presence of metallic Co.
