Ag/TiO2/freeze-dried graphene nanocomposites have been prepared via a facile one-step solvothermal method for the photocatalytic degradation of Rh B under visible light irradiation. During the solvothermal process, re...Ag/TiO2/freeze-dried graphene nanocomposites have been prepared via a facile one-step solvothermal method for the photocatalytic degradation of Rh B under visible light irradiation. During the solvothermal process, reduction of graphene oxide and loading of Ag/TiO2nanoparticles on graphene sheets were achieved. Investigation of chemical state of products showed that covering of Ag/TiO2surface with higher weight ratio of graphene resulting in that Ag metals in Ag/TiO2were oxidized to Ag2 O in nanocomposite structure after solvothermal process. Degree of photocatalytic activity enhancement strongly depends on the coverage of Ag/TiO2surface by porous graphene. The sample of 1 wt% porous graphene hybridized Ag/TiO2showed the highest photocatalytic activity, which is related to high migration efficiency of photoinduced of electrons and reduction of electron–hole recombination rate due to high electrical conductivity of graphene. Expanding of absorption to visible light region was ascribed to surface plasmon resonance effect of Ag metals and presence of graphene. Investigation of photocatalytic performance of formic acid as a dye-less organic pollutant showed that dye sensitization effect of Rh B molecules during evaluation of photocatalytic performance was negligible.展开更多
In this study,an Al2O3/MoS2 nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation method.The zeta potential measurements showed that small MoS2 particles have negative...In this study,an Al2O3/MoS2 nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation method.The zeta potential measurements showed that small MoS2 particles have negative potential and move toward the anode electrode.The nanoparticles of MoS2 were found to have a zeta potential of-25 mV,which prevents suspension in the solution.Thus,to produce an Al2O3/MoS2 nanocomposite,one has to use the microparticles of MoS2.The X-ray diffraction analyses showed that the produced coatings containedα-Al2O3,γ-Al2O3,and MoS2,and that the size of MoS2 particles can be reduced to 30 nm.It was observed that prolonged suspension in the electrolyte results in an enhanced formation of an Al2O3/MoS2 nanocomposite.Using the results,it was hypothesized that the mechanism of the formation of the Al2O3/MoS2 nanocomposite coating on the aluminum 1050 substrate is based on electrical energy discharge.展开更多
The objective of this research is to prepare specially designed surface texture on hard steel surface by electrochemical micromachining (EM) and to incorporate electroless plated Ag/MoS2 solid lubricant coating into t...The objective of this research is to prepare specially designed surface texture on hard steel surface by electrochemical micromachining (EM) and to incorporate electroless plated Ag/MoS2 solid lubricant coating into the dimples of EM textured steel surface to effectively reduce friction and wear of steel-steel contacts. The friction and wear behavior of the Ag/MoS2 solid lubricant coating on EM textured steel surface was evaluated in relation to the size and spacing of the dimples thereon. The microstructure of as-plated Ag/MoS2 solid lubricant coating and the morphology and elemental composition of the worn coating surface and counterface steel surface were analyzed by means of optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. It is found that electroless plated Ag/MoS2 coating is able to greatly reduce the friction and wear of the EM textured steel disc coupled with GCr15 steel ring, mainly because of the formation of solid self-lubricating layer on the EM textured steel surface and of transferred lubricating film on counterface steel surface. The diameter and spacing of the dimples are suggested as 500 μm for acquiring the best wear resistance of the hard steel discs after electrochemical micromachining treatment and electroless plating of Ag/MoS2 solid lubricating coating.展开更多
Semiconductoremetal nanocomposites have been widely investigated to modify the intrinsic properties of materials used for optoelectronic devices and sensing applications.In this study,a method for rapid synthesis of M...Semiconductoremetal nanocomposites have been widely investigated to modify the intrinsic properties of materials used for optoelectronic devices and sensing applications.In this study,a method for rapid synthesis of MoS_(2)-Ag nanocomposites via laser-assisted photoreduction was proposed.For the photoreduction process,we used AgNO_(3)solution as a metal source.Under laser irradiation,Ag ions were easily reduced on MoS_(2)by photo-generated electrons from MoS_(2).The optical properties of MoS_(2)-Ag nanocomposites were easily controlled by simple adjustment of the photoreduction time.To investigate the surface-enhanced Raman scattering(SERS)effect of the MoS_(2)-Ag nanocomposites,the SERS spectra of methylene blue(MB)on MoS_(2)-Ag nanocomposites were measured,and the nanocomposites were found to enhance the Raman scattering intensity of MB up to~106.Therefore,the laser-assisted photoreduction method has great potential for rapid synthesis and optical tuning of semiconductoremetal nanocomposites.展开更多
The alpha (α)-hematite (Fe2O3) as photoanode has been used for photoelectrochemical applications due to low bandgap, low cost, high chemical stability, nontoxicity, and abundance in nature. The doping with various tr...The alpha (α)-hematite (Fe2O3) as photoanode has been used for photoelectrochemical applications due to low bandgap, low cost, high chemical stability, nontoxicity, and abundance in nature. The doping with various transition metals, formation of nanostructured and nanocomposite of α-Fe2O3 have been attempted to enrich the carrier mobility, surface kinetics and carrier diffusion properties. The manuscript is an attempt to improve the photoelectrochemical properties of α-Fe2O3 by formation of nanocomposite with dichalcogenide (molybdenum disulfide (MoS2) nanomaterials. The nanocomposite of MoS2-α-Fe2O3 have been synthesized by varying the amount of MoS2 in sol-gel synthesis process. The nanocomposite MoS2-α-Fe2O3 materials were characterized using UV-visible, FTIR, SEM, X-ray diffraction, Raman and particle analyzer. The photoelectrochemical properties were investigated using cyclic voltammetry and chronoamperometry studies. The optical and structural properties of MoS2-α-Fe2O3 nanocomposite have been found to be dependent on MoS2 doping. The band gap has shifted whereas;the structure is more prominent as flower-like morphology, which is a result of doping of MoS2. The photocurrent is more pronounced with and without light exposition to MoS2-α-Fe2O3 based electrode in photoelectrochemical cell. We have understood the photoelectrochemical water splitting using nanocomposite α-Fe2O3-MoS2 through schematic representation based on experimental results. The enhanced photoelectrochemical properties of nanocomposite α-Fe2O3-MoS2 films have been observed as compared to pristine α-Fe2O3 and transition metal doped α-Fe2O3 nanostructured films.展开更多
Highly efficient Ag3PO4/MoS2 nanocomposite photocatalyst was synthe- sized using a wet chemical route with a low weight percentage of highly exfoliated MoS2 （0.1 wt.%） and monodispersed Ag3PO4 nanoparticles （-5.4 n...Highly efficient Ag3PO4/MoS2 nanocomposite photocatalyst was synthe- sized using a wet chemical route with a low weight percentage of highly exfoliated MoS2 （0.1 wt.%） and monodispersed Ag3PO4 nanoparticles （-5.4 nm）. The structural and optical properties of the nanocomposite were studied using various characterization techniques, such as XRD, TEM, Raman and absorption spectroscopy. The composite exhibits markedly enhanced photocatalytic activity with a low lamp power （60 W）. Using this composite, a high kinetic rate constant （k） value of 0.244 min^-1 was found. It was observed that -97.6% of dye degrade over the surface of nanocomposite catalyst within 15 min of illumination. The improved photocatalytic activity of Ag3PO4/MoS2 nanocomposite is attributed to the efficient interfacial charge separation, which was supported by the PL results. Large surface area of MoS2 nanosheets incorporated with well dispersed Ag3PO4 nanoparticles further increases charge separation, contributing to enhanced degradation efficiency. A possible mechanism for charge separation is also discussed.展开更多
Low-cost, highly efficient catalysts for hydrogen evolution reaction(HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides(2 D Mo S2)...Low-cost, highly efficient catalysts for hydrogen evolution reaction(HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides(2 D Mo S2) have been conducted due to their remarkable catalytic properties.However, most of the reported syntheses are time consuming,complicated and less efficient. The present work demonstrates the production of Mo S2/graphene catalyst via an ultra-fast(60 s) microwave-initiated approach. High specific surface area and conductivity of graphene delivers a favorable conductive network for the growth of Mo S2 nanosheets, along with rapid charge transfer kinetics. As-produced Mo S2/graphene nanocomposites exhibit superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of62 m V, high cathodic currents and a Tafel slope of43.3 m V/decade. Beyond excellent catalytic activity, Mo S2/graphene reveals long cycling stability with a very high cathodic current density of around 1000 m A cm^-2 at an overpotential of 250 m V. Moreover, the Mo S2/graphene-catalyst exhibits outstanding HER activities in a temperature range of 30 to 120°C with low activation energy of36.51 k J mol^-1, providing the opportunity of practical scalable processing.展开更多
Developing anatase/rutile phase-junction in Ti O_(2)to construct Z-scheme system is quite effective to improve its photoelectrochemical activity.In this work,the anatase/rutile phase-junction Ag/Ti O_(2)nanocomposites...Developing anatase/rutile phase-junction in Ti O_(2)to construct Z-scheme system is quite effective to improve its photoelectrochemical activity.In this work,the anatase/rutile phase-junction Ag/Ti O_(2)nanocomposites are developed as photocathodes for hydrogen production.The optimized Ag/Ti O_(2)nanocomposite achieves a high current density of 1.28 m A cm-2,an incident photon-to-current conversion efficiency(IPCE)of 10.8%,an applied bias photon-to-current efficiency(ABPE)of 0.32 at 390 nm and a charge carriers’lifetime up to 2000 s.Such enhancement on photoelectrochemical activity can be attributed to:(ⅰ)the generated Z-scheme system in the anatase/rutile phase-junction Ag/Ti O_(2)photocathode enhances the separation,diffusion and transformation of electron/hole pairs inside the structure,(ⅱ)Ag nanodots modification in the anatase/rutile phases leading to the tuned band gap with enhanced light absorption and(ⅲ)the formed Schottky barrier after Ag nanodots surface modification provides enough electron traps to avoid the recombination of photogenerated electrons and holes.Our results here suggest that developing phase-junction nanocomposite as photocathode will provide a new vision for their enhanced photoelectrochemical generation of hydrogen.展开更多
文摘Ag/TiO2/freeze-dried graphene nanocomposites have been prepared via a facile one-step solvothermal method for the photocatalytic degradation of Rh B under visible light irradiation. During the solvothermal process, reduction of graphene oxide and loading of Ag/TiO2nanoparticles on graphene sheets were achieved. Investigation of chemical state of products showed that covering of Ag/TiO2surface with higher weight ratio of graphene resulting in that Ag metals in Ag/TiO2were oxidized to Ag2 O in nanocomposite structure after solvothermal process. Degree of photocatalytic activity enhancement strongly depends on the coverage of Ag/TiO2surface by porous graphene. The sample of 1 wt% porous graphene hybridized Ag/TiO2showed the highest photocatalytic activity, which is related to high migration efficiency of photoinduced of electrons and reduction of electron–hole recombination rate due to high electrical conductivity of graphene. Expanding of absorption to visible light region was ascribed to surface plasmon resonance effect of Ag metals and presence of graphene. Investigation of photocatalytic performance of formic acid as a dye-less organic pollutant showed that dye sensitization effect of Rh B molecules during evaluation of photocatalytic performance was negligible.
文摘In this study,an Al2O3/MoS2 nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation method.The zeta potential measurements showed that small MoS2 particles have negative potential and move toward the anode electrode.The nanoparticles of MoS2 were found to have a zeta potential of-25 mV,which prevents suspension in the solution.Thus,to produce an Al2O3/MoS2 nanocomposite,one has to use the microparticles of MoS2.The X-ray diffraction analyses showed that the produced coatings containedα-Al2O3,γ-Al2O3,and MoS2,and that the size of MoS2 particles can be reduced to 30 nm.It was observed that prolonged suspension in the electrolyte results in an enhanced formation of an Al2O3/MoS2 nanocomposite.Using the results,it was hypothesized that the mechanism of the formation of the Al2O3/MoS2 nanocomposite coating on the aluminum 1050 substrate is based on electrical energy discharge.
基金supported by the the National NaturalScience Foundation of China(No.51205001)Foundation for Young Talents in College of Anhui Province(No.2012SQRL083ZD)the Talent Innovation Fund of An-hui Polytechnic University(No.S05305)
文摘The objective of this research is to prepare specially designed surface texture on hard steel surface by electrochemical micromachining (EM) and to incorporate electroless plated Ag/MoS2 solid lubricant coating into the dimples of EM textured steel surface to effectively reduce friction and wear of steel-steel contacts. The friction and wear behavior of the Ag/MoS2 solid lubricant coating on EM textured steel surface was evaluated in relation to the size and spacing of the dimples thereon. The microstructure of as-plated Ag/MoS2 solid lubricant coating and the morphology and elemental composition of the worn coating surface and counterface steel surface were analyzed by means of optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. It is found that electroless plated Ag/MoS2 coating is able to greatly reduce the friction and wear of the EM textured steel disc coupled with GCr15 steel ring, mainly because of the formation of solid self-lubricating layer on the EM textured steel surface and of transferred lubricating film on counterface steel surface. The diameter and spacing of the dimples are suggested as 500 μm for acquiring the best wear resistance of the hard steel discs after electrochemical micromachining treatment and electroless plating of Ag/MoS2 solid lubricating coating.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT).(NRF-2020R1A2C4002557)It was also supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education.(NRF-2021R1A6A3A13045573)Miri Choi at the KBSI(Chuncheon)is thanked for technical assistance with the FE-TEM analysis.
文摘Semiconductoremetal nanocomposites have been widely investigated to modify the intrinsic properties of materials used for optoelectronic devices and sensing applications.In this study,a method for rapid synthesis of MoS_(2)-Ag nanocomposites via laser-assisted photoreduction was proposed.For the photoreduction process,we used AgNO_(3)solution as a metal source.Under laser irradiation,Ag ions were easily reduced on MoS_(2)by photo-generated electrons from MoS_(2).The optical properties of MoS_(2)-Ag nanocomposites were easily controlled by simple adjustment of the photoreduction time.To investigate the surface-enhanced Raman scattering(SERS)effect of the MoS_(2)-Ag nanocomposites,the SERS spectra of methylene blue(MB)on MoS_(2)-Ag nanocomposites were measured,and the nanocomposites were found to enhance the Raman scattering intensity of MB up to~106.Therefore,the laser-assisted photoreduction method has great potential for rapid synthesis and optical tuning of semiconductoremetal nanocomposites.
文摘The alpha (α)-hematite (Fe2O3) as photoanode has been used for photoelectrochemical applications due to low bandgap, low cost, high chemical stability, nontoxicity, and abundance in nature. The doping with various transition metals, formation of nanostructured and nanocomposite of α-Fe2O3 have been attempted to enrich the carrier mobility, surface kinetics and carrier diffusion properties. The manuscript is an attempt to improve the photoelectrochemical properties of α-Fe2O3 by formation of nanocomposite with dichalcogenide (molybdenum disulfide (MoS2) nanomaterials. The nanocomposite of MoS2-α-Fe2O3 have been synthesized by varying the amount of MoS2 in sol-gel synthesis process. The nanocomposite MoS2-α-Fe2O3 materials were characterized using UV-visible, FTIR, SEM, X-ray diffraction, Raman and particle analyzer. The photoelectrochemical properties were investigated using cyclic voltammetry and chronoamperometry studies. The optical and structural properties of MoS2-α-Fe2O3 nanocomposite have been found to be dependent on MoS2 doping. The band gap has shifted whereas;the structure is more prominent as flower-like morphology, which is a result of doping of MoS2. The photocurrent is more pronounced with and without light exposition to MoS2-α-Fe2O3 based electrode in photoelectrochemical cell. We have understood the photoelectrochemical water splitting using nanocomposite α-Fe2O3-MoS2 through schematic representation based on experimental results. The enhanced photoelectrochemical properties of nanocomposite α-Fe2O3-MoS2 films have been observed as compared to pristine α-Fe2O3 and transition metal doped α-Fe2O3 nanostructured films.
文摘Highly efficient Ag3PO4/MoS2 nanocomposite photocatalyst was synthe- sized using a wet chemical route with a low weight percentage of highly exfoliated MoS2 （0.1 wt.%） and monodispersed Ag3PO4 nanoparticles （-5.4 nm）. The structural and optical properties of the nanocomposite were studied using various characterization techniques, such as XRD, TEM, Raman and absorption spectroscopy. The composite exhibits markedly enhanced photocatalytic activity with a low lamp power （60 W）. Using this composite, a high kinetic rate constant （k） value of 0.244 min^-1 was found. It was observed that -97.6% of dye degrade over the surface of nanocomposite catalyst within 15 min of illumination. The improved photocatalytic activity of Ag3PO4/MoS2 nanocomposite is attributed to the efficient interfacial charge separation, which was supported by the PL results. Large surface area of MoS2 nanosheets incorporated with well dispersed Ag3PO4 nanoparticles further increases charge separation, contributing to enhanced degradation efficiency. A possible mechanism for charge separation is also discussed.
基金supported by Auburn UniversityIntramural Grants Program (AU-IGP)
文摘Low-cost, highly efficient catalysts for hydrogen evolution reaction(HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides(2 D Mo S2) have been conducted due to their remarkable catalytic properties.However, most of the reported syntheses are time consuming,complicated and less efficient. The present work demonstrates the production of Mo S2/graphene catalyst via an ultra-fast(60 s) microwave-initiated approach. High specific surface area and conductivity of graphene delivers a favorable conductive network for the growth of Mo S2 nanosheets, along with rapid charge transfer kinetics. As-produced Mo S2/graphene nanocomposites exhibit superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of62 m V, high cathodic currents and a Tafel slope of43.3 m V/decade. Beyond excellent catalytic activity, Mo S2/graphene reveals long cycling stability with a very high cathodic current density of around 1000 m A cm^-2 at an overpotential of 250 m V. Moreover, the Mo S2/graphene-catalyst exhibits outstanding HER activities in a temperature range of 30 to 120°C with low activation energy of36.51 k J mol^-1, providing the opportunity of practical scalable processing.
基金supported financially by the Academy of Scientific Research and Technology(No.6618,ASRT,Egypt)the National Key R&D Program of China(No.2016YFA0202602),the National Natural Science Foundation of China(Nos.U1663225 and 21805220)+2 种基金the Fundamental Research Funds for the Central Universities(WUT:Nos.2019Ⅲ012GX and 2020Ⅲ002GX)the Hubei Provincial Natural Science Foundation(No.2018CFB242 and 2020CFB416)supported by the State Key Laboratory of Silicate Materials for Architectures and Center for Materials Research and Analysis at Wuhan University of Technology。
文摘Developing anatase/rutile phase-junction in Ti O_(2)to construct Z-scheme system is quite effective to improve its photoelectrochemical activity.In this work,the anatase/rutile phase-junction Ag/Ti O_(2)nanocomposites are developed as photocathodes for hydrogen production.The optimized Ag/Ti O_(2)nanocomposite achieves a high current density of 1.28 m A cm-2,an incident photon-to-current conversion efficiency(IPCE)of 10.8%,an applied bias photon-to-current efficiency(ABPE)of 0.32 at 390 nm and a charge carriers’lifetime up to 2000 s.Such enhancement on photoelectrochemical activity can be attributed to:(ⅰ)the generated Z-scheme system in the anatase/rutile phase-junction Ag/Ti O_(2)photocathode enhances the separation,diffusion and transformation of electron/hole pairs inside the structure,(ⅱ)Ag nanodots modification in the anatase/rutile phases leading to the tuned band gap with enhanced light absorption and(ⅲ)the formed Schottky barrier after Ag nanodots surface modification provides enough electron traps to avoid the recombination of photogenerated electrons and holes.Our results here suggest that developing phase-junction nanocomposite as photocathode will provide a new vision for their enhanced photoelectrochemical generation of hydrogen.
