Combining solar-driven H_(2) evolution with the selective conversion of the biomass platform compound 5-hydroxymethylfurfural(HMF)into high-value-added chemicals is promising.However,the development of this approach i...Combining solar-driven H_(2) evolution with the selective conversion of the biomass platform compound 5-hydroxymethylfurfural(HMF)into high-value-added chemicals is promising.However,the development of this approach is impeded by slow electron-hole separation and uncontrollable HMF conversion.In this study,we present a novel S-scheme sp^(2)-carbon COF(TFPD)/CdS heterojunction bifunctional photo-catalyst for the highly selective oxidation of HMF or C-C coupling,integrated with H_(2) production.The TFPD/CdS heterojunction forms an intrinsic electric field that facilitates efficient charge separation and migration during the photocatalytic process.Additionally,theoretical calculations and in situ diffuse re-flectance infrared Fourier transform spectroscopy(DRIFTS)reveal that the adsorption and desorption of(CHOH)C4 H_(2)(CHO)·radical on the catalyst surface are critical for the selective conversion of HMF.Con-sequently,depending on the reaction atmosphere,this photocatalyst selectively oxidizes HMF to 2,5-diformylfuran(DFF)with over 90%selectivity,or to 2,5-furandicarboxylic acid(FDCA)with approximately 80%selectivity.Notably,by controlling the solvent to promote the desorption of the(CHOH)C4 H_(2)(CHO)·radical,this system also produces HMF dimers with about 89%selectivity,alongside simultaneous H_(2) generation.This work pioneers the photocatalytic oxidation of HMF to C-C coupling products,providing insights into guiding radical reaction pathways for the selective photocatalytic conversion of HMF.展开更多
Cutting is an essential and complicated process in many fields.Efficient and low-consumption cutting operations are of great significance for environmental protection and energy conservation.The development of high pe...Cutting is an essential and complicated process in many fields.Efficient and low-consumption cutting operations are of great significance for environmental protection and energy conservation.The development of high performance cutting parts relies on a deep understanding of the cutting process and cutting mechanism.In this research,a new type of cutting test bench with high-speed photography was developed,and the cutting tests were conducted on the jute fiber bundle from quasi-static cutting at 10 mm/s to dynamic cutting in the speed range of 0.6-2.4 m/s.The cutting process was captured by a high-speed camera.Analysis shows that compression exists before quasi-static cutting,and the compression force curve with respect to the compression ratio follows an exponential function.The cutting speed has a significant effect on cutting energy.The cutting energy consumption is not a monotonous function of cutting speed owing to the combined effect of elastic deformation and friction of fibers.The cutting energy increases with increasing cutting speed in the range of 0.6-1.2 m/s due to the increase of the friction within fibers and the friction between the blade and fibers.The cutting energy decreases with increasing cutting speed in the range of 1.2-1.8 m/s,and tends to be a fixed value when the cutting speed exceeds 1.8 m/s due to the stabilized elastic deformation and friction coefficient.From the perspective of energy saving,it is meaningless to increase the blade speed excessively when cutting fiber bundles.展开更多
基金X.Li thanks the National Natural Science Foundation of China(Nos.22378148,and 21975084)the Natural Science Founda-tion of Guangdong Province(No.2024A1515012433)for their sup-port.R.Shen thanks the National Natural Science Foundation of China(No.2230082074).
文摘Combining solar-driven H_(2) evolution with the selective conversion of the biomass platform compound 5-hydroxymethylfurfural(HMF)into high-value-added chemicals is promising.However,the development of this approach is impeded by slow electron-hole separation and uncontrollable HMF conversion.In this study,we present a novel S-scheme sp^(2)-carbon COF(TFPD)/CdS heterojunction bifunctional photo-catalyst for the highly selective oxidation of HMF or C-C coupling,integrated with H_(2) production.The TFPD/CdS heterojunction forms an intrinsic electric field that facilitates efficient charge separation and migration during the photocatalytic process.Additionally,theoretical calculations and in situ diffuse re-flectance infrared Fourier transform spectroscopy(DRIFTS)reveal that the adsorption and desorption of(CHOH)C4 H_(2)(CHO)·radical on the catalyst surface are critical for the selective conversion of HMF.Con-sequently,depending on the reaction atmosphere,this photocatalyst selectively oxidizes HMF to 2,5-diformylfuran(DFF)with over 90%selectivity,or to 2,5-furandicarboxylic acid(FDCA)with approximately 80%selectivity.Notably,by controlling the solvent to promote the desorption of the(CHOH)C4 H_(2)(CHO)·radical,this system also produces HMF dimers with about 89%selectivity,alongside simultaneous H_(2) generation.This work pioneers the photocatalytic oxidation of HMF to C-C coupling products,providing insights into guiding radical reaction pathways for the selective photocatalytic conversion of HMF.
基金This work was financially supported by the National Key Research and Development Program of China(Grant No.2017YFD0700502)and the National Natural Science Foundation of China(Grant No.51705136 and 51375146).
文摘Cutting is an essential and complicated process in many fields.Efficient and low-consumption cutting operations are of great significance for environmental protection and energy conservation.The development of high performance cutting parts relies on a deep understanding of the cutting process and cutting mechanism.In this research,a new type of cutting test bench with high-speed photography was developed,and the cutting tests were conducted on the jute fiber bundle from quasi-static cutting at 10 mm/s to dynamic cutting in the speed range of 0.6-2.4 m/s.The cutting process was captured by a high-speed camera.Analysis shows that compression exists before quasi-static cutting,and the compression force curve with respect to the compression ratio follows an exponential function.The cutting speed has a significant effect on cutting energy.The cutting energy consumption is not a monotonous function of cutting speed owing to the combined effect of elastic deformation and friction of fibers.The cutting energy increases with increasing cutting speed in the range of 0.6-1.2 m/s due to the increase of the friction within fibers and the friction between the blade and fibers.The cutting energy decreases with increasing cutting speed in the range of 1.2-1.8 m/s,and tends to be a fixed value when the cutting speed exceeds 1.8 m/s due to the stabilized elastic deformation and friction coefficient.From the perspective of energy saving,it is meaningless to increase the blade speed excessively when cutting fiber bundles.
