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
The performances of heterogeneous catalysts can be effectively improved by optimizing the catalysts via appropriate structure design.Herein,we show that the catalysis of cuprous sulfide can be boosted by constructing ...The performances of heterogeneous catalysts can be effectively improved by optimizing the catalysts via appropriate structure design.Herein,we show that the catalysis of cuprous sulfide can be boosted by constructing the hybrid structure with Cu_(2)S nanoparticles on amorphous CuSx matrix(Cu_(2)S/CuSx).In the photocatalytic CO_(2) reduction under visible light irradiation,the Cu_(2)S/CuSx exhibited a CO production rate at 4.0μmol h-1 that is 12-fold higher than that of the general Cu_(2)S catalyst.Further characterizations reveal that the Cu_(2)S/CuSx has two reaction systems that realize the biomimetic catalysis,involving in the light reaction on the Cu_(2)S nanoparticle-CuSx matrix heterojunctions for proton/electron production,and the dark reaction on the defect-rich CuSx for CO_(2) reduction.The CuSx matrix could efficiently activate CO_(2) and stabilize the split hydrogen species to hinder undesired hydrogen evolution reaction,which benefits the proton-electron transfer to reduce CO_(2),a key step for bridging the two reaction systems.展开更多
Cl-containing cerium dioxide(Ce O2) catalysts have been found to exhibit unique catalytic activities. In the present work, using density functional theory calculations with the inclusion of on-site Coulomb correction,...Cl-containing cerium dioxide(Ce O2) catalysts have been found to exhibit unique catalytic activities. In the present work, using density functional theory calculations with the inclusion of on-site Coulomb correction, we systematically studied the effect of Cl on the physicochemical properties of Ce O2 surfaces by substituting one subsurface O with Cl. The calculated results show that substituting an O atom with a Cl atom results in structural distortion and the reduction of one surface Ce4+ cation to Ce3+. The protruding Ce3+ cation greatly improves the adsorption energy of O2 to produce an active O2- species, and maintains the catalytic oxidation cycle of CO on Ce O2(110). These results may help us obtain a better understanding of Cl-ceria interacting systems and provide some guidance for the design of effective Ce O2-based catalysts.展开更多
Development of active and stable catalysts for low-temperature CO oxidation has long been regarded as a hot topic.In this contribution,we used CeO_(2) with high-density surface pits as support to prepare an active and...Development of active and stable catalysts for low-temperature CO oxidation has long been regarded as a hot topic.In this contribution,we used CeO_(2) with high-density surface pits as support to prepare an active and stable Au/CeO_(2) catalyst by an adsorption-deposition method.The obtained 0.05 wt%Au/CeO_(2)-TD(where TD represents thermal decomposition)can maintain its activity at 80℃ for more than 20 h or even after calcination at 800℃ for 2 h.The characterization results showed that the high-density surface pits on CeO_(2)-TD play a decisive role in the stabilization of Au and enhancement of the redox property.This work may provide a new strategy to improve the stability of supported metal catalysts by a simple and conventional method.展开更多
Recently,ZnO-based gas sensors have been successfully fabricated and widely studied for their excellent sensitivity and selectivity,especially in CO detection.However,detailed explorations of their mechanisms are rath...Recently,ZnO-based gas sensors have been successfully fabricated and widely studied for their excellent sensitivity and selectivity,especially in CO detection.However,detailed explorations of their mechanisms are rather limited.Herein,aiming at clarifying the sensing mechanism,we carried out density functional theory(DFT)calculations to track down the CO adsorption and oxidation on the ZnO(1010)and(1120)surfaces.The calculated results show that the lattice O of ZnO(1010)is more reactive than that of ZnO(1120)for CO oxidation.From the calculated energetics and structures,the main reaction product on both surfaces can be determined to be CO2 rather than carbonate.Moreover,the surface conductivity changes during the adsorption and reaction processes of CO were also studied.For both ZnO(1010)and(1120),the conductivity would increase upon CO adsorption and decrease following CO oxidation,in consistence with the reported experimental results.This work can help understand the origins of ZnO-based sensors’performances and the development of novel gas sensors with higher sensitivity and selectivity.展开更多
Titanium dioxide(TiO_2) is one of the most widely studied transition metal oxides, especially for its unique performances in heterogeneous photocatalysis. Different phases of TiO_2 have been found to exhibit different...Titanium dioxide(TiO_2) is one of the most widely studied transition metal oxides, especially for its unique performances in heterogeneous photocatalysis. Different phases of TiO_2 have been found to exhibit different photo-activities, though the origins are still not fully understood. In this work, we use the density functional theory(DFT) calculations, corrected by on-site Coulomb and long-range dispersion interactions, to study the adsorptions of nitric oxide(NO) and oxygen(O2) molecules on the clean and hydrogenated anatase TiO_2(101) surfaces. We also compare the detailed calculated results regarding their structural, energetic and electronic properties with those obtained at rutile TiO_2(110). It has been found that the behaviors of the surface localized electrons being transferred from adsorbed H, as well as the adsorption behaviors of NO and O_2 are quite different at the two surfaces, which can be attributed to their characteristic local bonding structures around the surface hydroxyl. These results may also help explain the different photocatalytic activities of these two main facets of anatase and rutile展开更多
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supported by the National Key Research and Development Program of China(2018YFD1000806-01)the National Natural Science Foundation of China(21822203 and 21932006)+1 种基金the Natural Science Foundation of Zhejiang Province(LR18B030002)China Postdoctoral Science Foundation(2020M671020)。
文摘The performances of heterogeneous catalysts can be effectively improved by optimizing the catalysts via appropriate structure design.Herein,we show that the catalysis of cuprous sulfide can be boosted by constructing the hybrid structure with Cu_(2)S nanoparticles on amorphous CuSx matrix(Cu_(2)S/CuSx).In the photocatalytic CO_(2) reduction under visible light irradiation,the Cu_(2)S/CuSx exhibited a CO production rate at 4.0μmol h-1 that is 12-fold higher than that of the general Cu_(2)S catalyst.Further characterizations reveal that the Cu_(2)S/CuSx has two reaction systems that realize the biomimetic catalysis,involving in the light reaction on the Cu_(2)S nanoparticle-CuSx matrix heterojunctions for proton/electron production,and the dark reaction on the defect-rich CuSx for CO_(2) reduction.The CuSx matrix could efficiently activate CO_(2) and stabilize the split hydrogen species to hinder undesired hydrogen evolution reaction,which benefits the proton-electron transfer to reduce CO_(2),a key step for bridging the two reaction systems.
基金supported by the National Basic Research Program of China(2011CB808505)the National Natural Science Foundation of China(21322307,21421004)+1 种基金the"Shu Guang"project of Shanghai Municipal Education CommissionShanghai Education Development Foundation(13SG30)for financial support
文摘Cl-containing cerium dioxide(Ce O2) catalysts have been found to exhibit unique catalytic activities. In the present work, using density functional theory calculations with the inclusion of on-site Coulomb correction, we systematically studied the effect of Cl on the physicochemical properties of Ce O2 surfaces by substituting one subsurface O with Cl. The calculated results show that substituting an O atom with a Cl atom results in structural distortion and the reduction of one surface Ce4+ cation to Ce3+. The protruding Ce3+ cation greatly improves the adsorption energy of O2 to produce an active O2- species, and maintains the catalytic oxidation cycle of CO on Ce O2(110). These results may help us obtain a better understanding of Cl-ceria interacting systems and provide some guidance for the design of effective Ce O2-based catalysts.
基金financially supported by the National Key Research and Development Program of China(No.2016YFC0204300)the National Natural Science Foundation of China(Nos.21571061,21333003 and 21908079)Pujiang Program of the Shanghai Municipal Human Resources and Social Security Bureau(No.18PJD011)。
文摘Development of active and stable catalysts for low-temperature CO oxidation has long been regarded as a hot topic.In this contribution,we used CeO_(2) with high-density surface pits as support to prepare an active and stable Au/CeO_(2) catalyst by an adsorption-deposition method.The obtained 0.05 wt%Au/CeO_(2)-TD(where TD represents thermal decomposition)can maintain its activity at 80℃ for more than 20 h or even after calcination at 800℃ for 2 h.The characterization results showed that the high-density surface pits on CeO_(2)-TD play a decisive role in the stabilization of Au and enhancement of the redox property.This work may provide a new strategy to improve the stability of supported metal catalysts by a simple and conventional method.
基金supported by National Key R&D Program of China(No.2018YFA0208602)National Natural Science Foundation of China(Nos.21825301,21573067,21421004)Program of Shanghai Academic Research Leader(No.17XD1401400)。
文摘Recently,ZnO-based gas sensors have been successfully fabricated and widely studied for their excellent sensitivity and selectivity,especially in CO detection.However,detailed explorations of their mechanisms are rather limited.Herein,aiming at clarifying the sensing mechanism,we carried out density functional theory(DFT)calculations to track down the CO adsorption and oxidation on the ZnO(1010)and(1120)surfaces.The calculated results show that the lattice O of ZnO(1010)is more reactive than that of ZnO(1120)for CO oxidation.From the calculated energetics and structures,the main reaction product on both surfaces can be determined to be CO2 rather than carbonate.Moreover,the surface conductivity changes during the adsorption and reaction processes of CO were also studied.For both ZnO(1010)and(1120),the conductivity would increase upon CO adsorption and decrease following CO oxidation,in consistence with the reported experimental results.This work can help understand the origins of ZnO-based sensors’performances and the development of novel gas sensors with higher sensitivity and selectivity.
基金financial support from the National Natural Science Foundation of China (Nos. 21421004, 21573067, 91545103)Program of Shanghai Academic Research Leader (No. 17XD1401400)
文摘Titanium dioxide(TiO_2) is one of the most widely studied transition metal oxides, especially for its unique performances in heterogeneous photocatalysis. Different phases of TiO_2 have been found to exhibit different photo-activities, though the origins are still not fully understood. In this work, we use the density functional theory(DFT) calculations, corrected by on-site Coulomb and long-range dispersion interactions, to study the adsorptions of nitric oxide(NO) and oxygen(O2) molecules on the clean and hydrogenated anatase TiO_2(101) surfaces. We also compare the detailed calculated results regarding their structural, energetic and electronic properties with those obtained at rutile TiO_2(110). It has been found that the behaviors of the surface localized electrons being transferred from adsorbed H, as well as the adsorption behaviors of NO and O_2 are quite different at the two surfaces, which can be attributed to their characteristic local bonding structures around the surface hydroxyl. These results may also help explain the different photocatalytic activities of these two main facets of anatase and rutile
