Electrochemical reduction of molecular O2 to hydrogen peroxide(H2O2)offers a promising solution for water purification and environmental remediation.Here,we design a hierarchical free-standing single-Co-atom(with Co-N...Electrochemical reduction of molecular O2 to hydrogen peroxide(H2O2)offers a promising solution for water purification and environmental remediation.Here,we design a hierarchical free-standing single-Co-atom(with Co-N4 coordination)electrode for oxygen reduction reaction(ORR)via a two-electron pathway to make H2O2 in acidic media.The current density of the single-Co-atom electrode reached 51 mA/cm2 at 0.1 V vs reversible hydrogen electrode,lasting for more than 10 hours of continuous operation with H2O2 selectivity greater than 80%.Toward practical application,the single-Co-atom electrode was directly used to assemble an electrochemical cell to produce H2O2 at a rate of 676 mol/kgcat/h with a cell voltage of about 1.6 V.展开更多
Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2...Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.展开更多
During hot rolling process metals will inevitably oxidize because of high temperature and air condition. In order to guarantee the surface quality, acid pickling is applied to remove the oxide scale while waste acid w...During hot rolling process metals will inevitably oxidize because of high temperature and air condition. In order to guarantee the surface quality, acid pickling is applied to remove the oxide scale while waste acid will do harm to the environment. Faced with the problem, by means of reduction process of hot-rolled plates, the oxide scale will be reduced to iron, so that acid pickling is unnecessary. One pass cold rolling procedure was applied. The compres- sion ratios of hot-rolled plates with oxide scale were 10%, 18%, 26% and 31%, respectively. After that, samples mentioned above including a sample without deformation were separately reduced under hydrogen atmosphere condi- tion （5 % H2 ＋95 % Ar in volume percent） at 600-1 000 ℃. The thermal gravimetric apparatus （TGA） was used to establish accurate experimental condition and obtain complete mass loss data. Field emission electron probe microa- nalysis （EPMA） was applied to analyze scale morphology change and composition distribution through the oxide scale. It was found that the sample with 26% compression ratio could be reduced completely at 900 ℃which was favorable to galvanization.展开更多
Electrophoretic deposition in conjunction with electrochemical reduction was used to make flexible free-standing graphene-like films. Firstly, graphene oxide （GO） film was deposited on graphite substrate by electrop...Electrophoretic deposition in conjunction with electrochemical reduction was used to make flexible free-standing graphene-like films. Firstly, graphene oxide （GO） film was deposited on graphite substrate by electrophoretic deposition method, and then reduced by subsequent electrochemical reduction of GO to obtain reduced GO （ERGO） film with high electrochemical performance. The morphology, structure and electrochemical performance of the prepared graphene-like film were confirmed by SEM, XRD and FT-IR. These unique materials were found to provide high specific capacitance and good cycling stability. The high specific capacitance of 254 F/g was obtained from cyclic voltammetry measurement at a scan rate of 10 mV/s. When the current density increased to 83.3 A/g, the specific capacitance values still remained 132 F/g. Meanwhile, the high powder density of 39.1 kW/kg was measured at energy density of 11.8 W-h/kg in 1 mol/L H2SO4 solution. Furthermore, at a constant scan rate of 50 mV/s, 97.02% of its capacitance was retained for 1000 cycles. These promising results were attributed to the unique assembly structure of graphene film and low contact resistance, which indicated their potential application to electrochemical capacitors.展开更多
This study investigated the facilitation of Cr(VI)decontamination to the formation of persistent free radicals(PFRs)on rice husk derived biochar.It was found that Cr(VI)remediation by biochar facilitated the productio...This study investigated the facilitation of Cr(VI)decontamination to the formation of persistent free radicals(PFRs)on rice husk derived biochar.It was found that Cr(VI)remediation by biochar facilitated the production of PFRs,which increased with the concentration of treated Cr(VI).However,excessive Cr(VI)would induce their decay.Biochar with high pyrolysis temperature possessed great performance to Cr(VI)removal,which was mainly originated from its reduction by biochar from Inductively Coupled Plasma Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.And the corresponding generation of PFRs on biochar was primarily ascribed to the oxidization of phenolic hydroxyl groups by Cr(VI)from Fourier Transform Infrared Spectroscopy analysis,which was further verified by the H2O2 treatment experiments.The findings of this study will help to illustrate the transformation of reactive functional groups on biochar and provide a new insight into the role of biochar in environmental remediation.展开更多
Biochar is a well-known material for pollutant removal owing to its low cost and rich surface functionality. A kind of highly active substance, called environmentally persistent free radicals(EPFRs), can be produced i...Biochar is a well-known material for pollutant removal owing to its low cost and rich surface functionality. A kind of highly active substance, called environmentally persistent free radicals(EPFRs), can be produced in the preparation process of biochar, playing an important role in the removal of pollutants.In this study, sludge-derived biochars(SBC_(120) and SBC_(270)) were prepared by the hydrothermal carbonization under two temperatures(120℃ and 270℃) to investigate their removal abilities of Cr(Ⅵ). The maximum removal amounts of Cr(Ⅵ) by SBC_(120) and SBC_(270) were 16.58 and 22.93 mg·g^(-1), respectively. It was further revealed that the appearance of Cr(Ⅲ), as a result of EPFRs on sludge-derived biochar(SBC) transferred electrons to Cr(Ⅵ) in neutral solutions. That is to say, oxygen-centered(O-centered) EPFRs on SBC_(120) and carbon-centered(C-centered) EPFRs on SBC_(270) all could be used as electron donors to Cr(Ⅵ) to make it become Cr(Ⅲ). This study not only provides a theoretical basis for the mechanism of pollutants removal by sludge-derived biochar but also offers a new perspective on the direct effect of EPFRs on pollutants.展开更多
Expanding the application scenario for rechargeable batteries is the key to the terminal utilization of renewable energy.Enabling zinc–air batteries at low temperatures is drawing increasing attention,yet the low-tem...Expanding the application scenario for rechargeable batteries is the key to the terminal utilization of renewable energy.Enabling zinc–air batteries at low temperatures is drawing increasing attention,yet the low-temperature working feasibility of zinc–air batteries with noble metalfree electrocatalysts remains indistinct.In this contribution,the low-temperature performances of zinc–air batteries with noble metal-free electrocatalysts are comprehensively investigated.Armed with a representative noble metal-free bifunctional oxygen electrocatalyst,the zinc–air batteries demonstrate satisfactory yet relatively depressed performance at low temperatures,compared with that at room temperatures.The reduced electrolyte conductivity is identified as one of the limiting factors for the reduced low-temperature performance.Furthermore,electrolyte engineering via solvation structure regulation is performed on the zinc–air batteries with noblemetal-free electrocatalysts,where an improved low-temperature performance is achieved.This work reveals the compatibility between noble metal-free electrocatalysts and low-temperature feasibility/low-temperature performance enhancement strategies for zinc–air batteries and affords new opportunities to satisfy low-cost and efficient energy storage at harsh working conditions.展开更多
The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggis...The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.展开更多
基金This study was supported by the funds from the Singapore Ministry of Education Academic Research Fund,Tier 1:RG111/15 and RG10/16 and Tier 2:MOE2016-T2-2 to 004.
文摘Electrochemical reduction of molecular O2 to hydrogen peroxide(H2O2)offers a promising solution for water purification and environmental remediation.Here,we design a hierarchical free-standing single-Co-atom(with Co-N4 coordination)electrode for oxygen reduction reaction(ORR)via a two-electron pathway to make H2O2 in acidic media.The current density of the single-Co-atom electrode reached 51 mA/cm2 at 0.1 V vs reversible hydrogen electrode,lasting for more than 10 hours of continuous operation with H2O2 selectivity greater than 80%.Toward practical application,the single-Co-atom electrode was directly used to assemble an electrochemical cell to produce H2O2 at a rate of 676 mol/kgcat/h with a cell voltage of about 1.6 V.
基金supported by the Jiangsu Provincial Double-Innovation Doctor Program(JSSCBS20210996).
文摘Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.
基金Item Sponsored by National High Technology Research and Development Program of China(2011BAE13B04)National Natural Science Foundation of China(51204047)
文摘During hot rolling process metals will inevitably oxidize because of high temperature and air condition. In order to guarantee the surface quality, acid pickling is applied to remove the oxide scale while waste acid will do harm to the environment. Faced with the problem, by means of reduction process of hot-rolled plates, the oxide scale will be reduced to iron, so that acid pickling is unnecessary. One pass cold rolling procedure was applied. The compres- sion ratios of hot-rolled plates with oxide scale were 10%, 18%, 26% and 31%, respectively. After that, samples mentioned above including a sample without deformation were separately reduced under hydrogen atmosphere condi- tion （5 % H2 ＋95 % Ar in volume percent） at 600-1 000 ℃. The thermal gravimetric apparatus （TGA） was used to establish accurate experimental condition and obtain complete mass loss data. Field emission electron probe microa- nalysis （EPMA） was applied to analyze scale morphology change and composition distribution through the oxide scale. It was found that the sample with 26% compression ratio could be reduced completely at 900 ℃which was favorable to galvanization.
基金Projects(21361020,21061012)supported by the National Natural Science Foundation of ChinaProject(NZ12156)supported by the Natural Science Foundation of Ningxia,ChinaProject(N-09-13)supported by Project of State Key Laboratory of Catalysis,Dalian Institute of Chemical Physics of the Chinese Academy of Sciences
文摘Electrophoretic deposition in conjunction with electrochemical reduction was used to make flexible free-standing graphene-like films. Firstly, graphene oxide （GO） film was deposited on graphite substrate by electrophoretic deposition method, and then reduced by subsequent electrochemical reduction of GO to obtain reduced GO （ERGO） film with high electrochemical performance. The morphology, structure and electrochemical performance of the prepared graphene-like film were confirmed by SEM, XRD and FT-IR. These unique materials were found to provide high specific capacitance and good cycling stability. The high specific capacitance of 254 F/g was obtained from cyclic voltammetry measurement at a scan rate of 10 mV/s. When the current density increased to 83.3 A/g, the specific capacitance values still remained 132 F/g. Meanwhile, the high powder density of 39.1 kW/kg was measured at energy density of 11.8 W-h/kg in 1 mol/L H2SO4 solution. Furthermore, at a constant scan rate of 50 mV/s, 97.02% of its capacitance was retained for 1000 cycles. These promising results were attributed to the unique assembly structure of graphene film and low contact resistance, which indicated their potential application to electrochemical capacitors.
文摘This study investigated the facilitation of Cr(VI)decontamination to the formation of persistent free radicals(PFRs)on rice husk derived biochar.It was found that Cr(VI)remediation by biochar facilitated the production of PFRs,which increased with the concentration of treated Cr(VI).However,excessive Cr(VI)would induce their decay.Biochar with high pyrolysis temperature possessed great performance to Cr(VI)removal,which was mainly originated from its reduction by biochar from Inductively Coupled Plasma Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.And the corresponding generation of PFRs on biochar was primarily ascribed to the oxidization of phenolic hydroxyl groups by Cr(VI)from Fourier Transform Infrared Spectroscopy analysis,which was further verified by the H2O2 treatment experiments.The findings of this study will help to illustrate the transformation of reactive functional groups on biochar and provide a new insight into the role of biochar in environmental remediation.
基金supported by the Beijing Municipal Natural Science Foundation (8202007)the National Natural Science Foundation of China (52170148)。
文摘Biochar is a well-known material for pollutant removal owing to its low cost and rich surface functionality. A kind of highly active substance, called environmentally persistent free radicals(EPFRs), can be produced in the preparation process of biochar, playing an important role in the removal of pollutants.In this study, sludge-derived biochars(SBC_(120) and SBC_(270)) were prepared by the hydrothermal carbonization under two temperatures(120℃ and 270℃) to investigate their removal abilities of Cr(Ⅵ). The maximum removal amounts of Cr(Ⅵ) by SBC_(120) and SBC_(270) were 16.58 and 22.93 mg·g^(-1), respectively. It was further revealed that the appearance of Cr(Ⅲ), as a result of EPFRs on sludge-derived biochar(SBC) transferred electrons to Cr(Ⅵ) in neutral solutions. That is to say, oxygen-centered(O-centered) EPFRs on SBC_(120) and carbon-centered(C-centered) EPFRs on SBC_(270) all could be used as electron donors to Cr(Ⅵ) to make it become Cr(Ⅲ). This study not only provides a theoretical basis for the mechanism of pollutants removal by sludge-derived biochar but also offers a new perspective on the direct effect of EPFRs on pollutants.
基金the Key Research and Development Program of Yunnan Province(grant no.202103AA080019)S&T Program of Hebei(grant no.22344402D)+1 种基金National Natural Science Foundation of China(grant no.22109007)Beijing Institute of Technology Research Fund Program for Young Scholars,and the Tsinghua University Initiative Scientific Research Program.
文摘Expanding the application scenario for rechargeable batteries is the key to the terminal utilization of renewable energy.Enabling zinc–air batteries at low temperatures is drawing increasing attention,yet the low-temperature working feasibility of zinc–air batteries with noble metalfree electrocatalysts remains indistinct.In this contribution,the low-temperature performances of zinc–air batteries with noble metal-free electrocatalysts are comprehensively investigated.Armed with a representative noble metal-free bifunctional oxygen electrocatalyst,the zinc–air batteries demonstrate satisfactory yet relatively depressed performance at low temperatures,compared with that at room temperatures.The reduced electrolyte conductivity is identified as one of the limiting factors for the reduced low-temperature performance.Furthermore,electrolyte engineering via solvation structure regulation is performed on the zinc–air batteries with noblemetal-free electrocatalysts,where an improved low-temperature performance is achieved.This work reveals the compatibility between noble metal-free electrocatalysts and low-temperature feasibility/low-temperature performance enhancement strategies for zinc–air batteries and affords new opportunities to satisfy low-cost and efficient energy storage at harsh working conditions.
基金supported by the start-up fund from Kunming University of Science and Technology,the National Natural Science Foundation of China (Grants 52102046,51872293,52130209,52072375)Liaoning Revitalization Talents Program (XLYC2002037)Basic Research Project of Natural Science Foundation of Shandong Province,China (ZR2019ZD49).
文摘The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.
