Cr-Cu-N coatings with copper content from 0 at%to 6.8 at%were deposited on silicon and M2 steel by ion beam assisted magnetron sputtering.The microstructure and composition of the coatings were characterized using SEM...Cr-Cu-N coatings with copper content from 0 at%to 6.8 at%were deposited on silicon and M2 steel by ion beam assisted magnetron sputtering.The microstructure and composition of the coatings were characterized using SEM,GDOES,XRD and XPS.The mechanical properties of the coatings were tested on a standard hardness tester.The tribological behavior of the coatings in dry wear condition was studied by means of ball-on-disc wear test.The experimental results show that addition of copper can restrict the columnar crystal growing to a certain degree.XRD and XPS analysis indicate that coatings are mainly composed of Cr and CrN phase.Cu is mainly existed in a free state in the coatings.Copper adding has no obvious effects on the hardness of the coatings.However,the coatings fracture toughness can be improved by doped copper.The coefficient of friction of the coatings against bearing steel is in the range of 0.25-0.6 changing with the copper content.The coating with 2.6 at%copper shows the lowest coefficient of friction about 0.25 and wear rate which is about one tenth of that of the coating with 6.8 at%copper.The higher coefficient of friction and wear rate of the coating with 6.8at%copper may be attributed to its lower bonding strength.展开更多
Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphen...Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphene-modified non-compensated Cu/N-co-doped titanium dioxide(Cu-N-TiO_(2)/rGO)photocatalyst was designed for the efficient synthesis of H_(2)O_(2) via a dual-channel pathway.Precise modulation of the TiO_(2) conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals.This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements.Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti^(3+)ions,the photogenerated charge recombination centers.The non-compensated doping of N effectively increased the solubility of Cu^(2+)ions in the titanium dioxide lattice,enhanced the adsorption of hydroxyl radical intermediates,and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H_(2)O_(2).In addition,the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites,creating conditions for dual-channel reactions.The experimental results showed that the H_(2)O_(2) yield of Cu-N-TiO_(2)/rGO under simulated sunlight reached 1266.7μmol/L,which was 25.2 times higher than that of pristine TiO_(2).This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization,which provided a new idea for the design of dual-channel H_(2)O_(2) production photocatalysts.展开更多
Atomic-level active site design and modulation are challenging in catalysis,and atomically precise copper nanoclusters(NCs)present a promising solution due to the well-defined structures and tunable active sites.We re...Atomic-level active site design and modulation are challenging in catalysis,and atomically precise copper nanoclusters(NCs)present a promising solution due to the well-defined structures and tunable active sites.We report two novel Cu NCs with formamidinate protecting ligands:[Cu_(33)H18(Me-dpf)_(12)](BF_(4))_(3)(Cu_(33-1),Me-Hdpf=N,N′-di(5-methyl-2-pyridinyl)formamidine)and[Cu_(33)H_(16)(Me-dpf)_(12)C_(l2)](BF_(4))_(3)(Cu_(33-2)).In both clusters,all Cu atoms are N-coordinated,forming abundant active Cu-N sites for CO_(2) reduction reaction(CO_(2)RR).Both Cu_(33) NCs with highly active Cu^(+)-N sites exhibit remarkable CO_(2)-to-CH_(4) conversion efficiency.Cu_(33-1) shows notable CO_(2)-to-CH_(4) selectivity(57.7%)and stability(FECH_(4)>50% after 12 h),achieving a remarkable conversion rate of 0.517μmol cm^(-2) s^(-1) in a flow cell and surpassing all known NC catalysts.Detailed in-situ spectroscopies revealed that these precisely engineered Cu^(+)-N sites stabilize key intermediates*CHO and*OCH_(2),significantly promoting CH_(4) formation.This study underscores precise engineering of active sites,providing valuable insights for designing highly efficient NC catalysts for CO_(2) conversion.展开更多
基金The National Natural Science Foundation of China(50771070)Shanxi Province Science and Technology Key Project(20100321078-02)
文摘Cr-Cu-N coatings with copper content from 0 at%to 6.8 at%were deposited on silicon and M2 steel by ion beam assisted magnetron sputtering.The microstructure and composition of the coatings were characterized using SEM,GDOES,XRD and XPS.The mechanical properties of the coatings were tested on a standard hardness tester.The tribological behavior of the coatings in dry wear condition was studied by means of ball-on-disc wear test.The experimental results show that addition of copper can restrict the columnar crystal growing to a certain degree.XRD and XPS analysis indicate that coatings are mainly composed of Cr and CrN phase.Cu is mainly existed in a free state in the coatings.Copper adding has no obvious effects on the hardness of the coatings.However,the coatings fracture toughness can be improved by doped copper.The coefficient of friction of the coatings against bearing steel is in the range of 0.25-0.6 changing with the copper content.The coating with 2.6 at%copper shows the lowest coefficient of friction about 0.25 and wear rate which is about one tenth of that of the coating with 6.8 at%copper.The higher coefficient of friction and wear rate of the coating with 6.8at%copper may be attributed to its lower bonding strength.
文摘Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphene-modified non-compensated Cu/N-co-doped titanium dioxide(Cu-N-TiO_(2)/rGO)photocatalyst was designed for the efficient synthesis of H_(2)O_(2) via a dual-channel pathway.Precise modulation of the TiO_(2) conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals.This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements.Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti^(3+)ions,the photogenerated charge recombination centers.The non-compensated doping of N effectively increased the solubility of Cu^(2+)ions in the titanium dioxide lattice,enhanced the adsorption of hydroxyl radical intermediates,and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H_(2)O_(2).In addition,the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites,creating conditions for dual-channel reactions.The experimental results showed that the H_(2)O_(2) yield of Cu-N-TiO_(2)/rGO under simulated sunlight reached 1266.7μmol/L,which was 25.2 times higher than that of pristine TiO_(2).This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization,which provided a new idea for the design of dual-channel H_(2)O_(2) production photocatalysts.
基金supported by the National Key R&D Program of China(grant no.2022YFA1503900)the National Natural Science Foundation of China(grant nos.92361301 and 22401114)+1 种基金the Basic Research Program of Jiangsu(grant no.BK20241604)the Fundamental Research Funds for the Central Universities(grant no.JUSRP202401026).
文摘Atomic-level active site design and modulation are challenging in catalysis,and atomically precise copper nanoclusters(NCs)present a promising solution due to the well-defined structures and tunable active sites.We report two novel Cu NCs with formamidinate protecting ligands:[Cu_(33)H18(Me-dpf)_(12)](BF_(4))_(3)(Cu_(33-1),Me-Hdpf=N,N′-di(5-methyl-2-pyridinyl)formamidine)and[Cu_(33)H_(16)(Me-dpf)_(12)C_(l2)](BF_(4))_(3)(Cu_(33-2)).In both clusters,all Cu atoms are N-coordinated,forming abundant active Cu-N sites for CO_(2) reduction reaction(CO_(2)RR).Both Cu_(33) NCs with highly active Cu^(+)-N sites exhibit remarkable CO_(2)-to-CH_(4) conversion efficiency.Cu_(33-1) shows notable CO_(2)-to-CH_(4) selectivity(57.7%)and stability(FECH_(4)>50% after 12 h),achieving a remarkable conversion rate of 0.517μmol cm^(-2) s^(-1) in a flow cell and surpassing all known NC catalysts.Detailed in-situ spectroscopies revealed that these precisely engineered Cu^(+)-N sites stabilize key intermediates*CHO and*OCH_(2),significantly promoting CH_(4) formation.This study underscores precise engineering of active sites,providing valuable insights for designing highly efficient NC catalysts for CO_(2) conversion.
