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
Acidizing treatment is considered as a significant process in the oil well stimulations to form wormholes in carbonate formation in order to enhance the reservoir fluid production.Obtaining the number of pore volumes ...Acidizing treatment is considered as a significant process in the oil well stimulations to form wormholes in carbonate formation in order to enhance the reservoir fluid production.Obtaining the number of pore volumes to breakthrough is an important objective in matrix acidizing,for it contributes to determining the wormhole characteristics such as type,shape,and size.Finding this number in experimental works requires a considerable amount of time,energy and cost.Therefore,this study aimed to establish an analytical method in which a reasonable result is achieved for the number of pore volumes to breakthrough.This purpose is accomplished by solely implementing acid and formation properties without performing any experimental works.The process of wormhole creation is done through developing a numerical model by utilizing the conservation of mass law method in which the carbonate core is considered as a closed system and the overall mass in the system as constant during the acid injection process.Furthermore,a constant number is added to the mathematical part of the model in order to eliminate the dimensionless Damk鰄ler number which is supposed to be calculated experimentally.The results of the numerical procedure of the model are further compared to four other experimental works,which led to calculating the average accuracy of this model that is shown to be 95.98%.This study puts forward a comprehensive numerical model to estimate the number of pore volumes to breakthrough with an acceptable accuracy rate merely through implementing known acid and core properties.展开更多
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.
文摘Acidizing treatment is considered as a significant process in the oil well stimulations to form wormholes in carbonate formation in order to enhance the reservoir fluid production.Obtaining the number of pore volumes to breakthrough is an important objective in matrix acidizing,for it contributes to determining the wormhole characteristics such as type,shape,and size.Finding this number in experimental works requires a considerable amount of time,energy and cost.Therefore,this study aimed to establish an analytical method in which a reasonable result is achieved for the number of pore volumes to breakthrough.This purpose is accomplished by solely implementing acid and formation properties without performing any experimental works.The process of wormhole creation is done through developing a numerical model by utilizing the conservation of mass law method in which the carbonate core is considered as a closed system and the overall mass in the system as constant during the acid injection process.Furthermore,a constant number is added to the mathematical part of the model in order to eliminate the dimensionless Damk鰄ler number which is supposed to be calculated experimentally.The results of the numerical procedure of the model are further compared to four other experimental works,which led to calculating the average accuracy of this model that is shown to be 95.98%.This study puts forward a comprehensive numerical model to estimate the number of pore volumes to breakthrough with an acceptable accuracy rate merely through implementing known acid and core properties.
