As by-products of petroleum refining,heavy oils are characterized by a high carbon content,low cost and great variability,making them competitive precursors for the anodes of potassium ion batteries(PIBs).However,the ...As by-products of petroleum refining,heavy oils are characterized by a high carbon content,low cost and great variability,making them competitive precursors for the anodes of potassium ion batteries(PIBs).However,the relationship between heavy oil composition and potassium storage performance remains unclear.Using heavy oils containing distinct chemical groups as the carbon source,namely fluid catalytic cracking slurry(FCCS),petroleum asphalt(PA)and deoiled asphalt(DOA),three carbon nanosheets(CNS)were prepared through a molten salt method,and used as the anodes for PIBs.The composition of the heavy oil determines the lamellar thicknesses,sp3-C/sp2-C ratio and defect concentration,thereby affecting the potassium storage performance.The high content of aromatic hydrocarbons and moderate amount of heavy component moieties in FCCS produce carbon nanosheets(CNS-FCCS)that have a smaller layer thickness,larger interlayer spacing(0.372 nm),and increased number of folds than in CNS derived from the other three precursors.These features give it faster charge/ion transfer,more potassium storage sites and better reaction kinetics.CNS-FCCS has a remarkable K^(+)storage capacity(248.7 mAh g^(-1) after 100 cycles at 0.1 A g^(-1)),long cycle lifespan(190.8 mAh g^(-1) after 800 cycles at 1.0 A g^(-1))and excellent rate capability,ranking it among the best materials for this application.This work sheds light on the influence of heavy oil composition on carbon structure and electrochemical performance,and provides guidance for the design and development of advanced heavy oil-derived carbon electrodes for PIBs.展开更多
Crystalline carbon nitride(CCN)prepared by a molten-salt method is attracting increased attention because of its promising properties and excellent photocatalytic activity.In this work,we further improve the crystalli...Crystalline carbon nitride(CCN)prepared by a molten-salt method is attracting increased attention because of its promising properties and excellent photocatalytic activity.In this work,we further improve the crystallinity of CCN through synthesis by the molten-salt method under the action of aqueous hydrochloric acid(HCl)solution.Our results showed that the crystallinity of the as-prepared samples increased with increasing HCl concentration and reached the maximum value at 0.1 mol L^-1.This can be attributed to the removal of some potassium ions(K+)from the terminal amino groups of CCN by the aqueous HCl solution,which results in a release of the polymerization sites.As a result,the crystallinity of the as-prepared samples further increased.Moreover,the obtained 0.1 highly crystalline carbon nitride(0.1HCCN;treated with 0.1 mol L^-1 aqueous HCl solution)exhibited an excellent photocatalytic hydrogen evolution of 683.54μmol h^-1 g^-1 and a quantum efficiency of 6.6%at 420 nm with triethanolamine as the sacrificial agent.This photocatalytic hydrogen evolution was 2 and 10 times higher than those of CCN and bulk carbon nitride,respectively.The enhanced photocatalytic activity was attributed to the improved crystallinity and intercalation of K+into the xHCCN interlayer.The improved crystallinity can decrease the number of surface defects and hydrogen bonds in the as-prepared sample,thereby increasing the mobility of the photoinduced carriers and reducing the recombination sites of the electron-hole pairs.The K+intercalated into the xHCCN interlayer also promoted the transfer of the photoinduced electrons because these ions can increase the electronic delocalization and extend theπ-conjugated systems.This study may provide new insights into the further development of the molten-salt method.展开更多
文摘As by-products of petroleum refining,heavy oils are characterized by a high carbon content,low cost and great variability,making them competitive precursors for the anodes of potassium ion batteries(PIBs).However,the relationship between heavy oil composition and potassium storage performance remains unclear.Using heavy oils containing distinct chemical groups as the carbon source,namely fluid catalytic cracking slurry(FCCS),petroleum asphalt(PA)and deoiled asphalt(DOA),three carbon nanosheets(CNS)were prepared through a molten salt method,and used as the anodes for PIBs.The composition of the heavy oil determines the lamellar thicknesses,sp3-C/sp2-C ratio and defect concentration,thereby affecting the potassium storage performance.The high content of aromatic hydrocarbons and moderate amount of heavy component moieties in FCCS produce carbon nanosheets(CNS-FCCS)that have a smaller layer thickness,larger interlayer spacing(0.372 nm),and increased number of folds than in CNS derived from the other three precursors.These features give it faster charge/ion transfer,more potassium storage sites and better reaction kinetics.CNS-FCCS has a remarkable K^(+)storage capacity(248.7 mAh g^(-1) after 100 cycles at 0.1 A g^(-1)),long cycle lifespan(190.8 mAh g^(-1) after 800 cycles at 1.0 A g^(-1))and excellent rate capability,ranking it among the best materials for this application.This work sheds light on the influence of heavy oil composition on carbon structure and electrochemical performance,and provides guidance for the design and development of advanced heavy oil-derived carbon electrodes for PIBs.
基金supported by the National Natural Science Foundation of China(51672099,21403079)Sichuan Science and Technology Program(2019JDRC0027)Fundamental Research Funds for the Central Universities(2017-QR-25)~~
文摘Crystalline carbon nitride(CCN)prepared by a molten-salt method is attracting increased attention because of its promising properties and excellent photocatalytic activity.In this work,we further improve the crystallinity of CCN through synthesis by the molten-salt method under the action of aqueous hydrochloric acid(HCl)solution.Our results showed that the crystallinity of the as-prepared samples increased with increasing HCl concentration and reached the maximum value at 0.1 mol L^-1.This can be attributed to the removal of some potassium ions(K+)from the terminal amino groups of CCN by the aqueous HCl solution,which results in a release of the polymerization sites.As a result,the crystallinity of the as-prepared samples further increased.Moreover,the obtained 0.1 highly crystalline carbon nitride(0.1HCCN;treated with 0.1 mol L^-1 aqueous HCl solution)exhibited an excellent photocatalytic hydrogen evolution of 683.54μmol h^-1 g^-1 and a quantum efficiency of 6.6%at 420 nm with triethanolamine as the sacrificial agent.This photocatalytic hydrogen evolution was 2 and 10 times higher than those of CCN and bulk carbon nitride,respectively.The enhanced photocatalytic activity was attributed to the improved crystallinity and intercalation of K+into the xHCCN interlayer.The improved crystallinity can decrease the number of surface defects and hydrogen bonds in the as-prepared sample,thereby increasing the mobility of the photoinduced carriers and reducing the recombination sites of the electron-hole pairs.The K+intercalated into the xHCCN interlayer also promoted the transfer of the photoinduced electrons because these ions can increase the electronic delocalization and extend theπ-conjugated systems.This study may provide new insights into the further development of the molten-salt method.
