Ultra-thin α-Fe2O3(hematite) films have been deposited by radio frequency(RF) sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power an...Ultra-thin α-Fe2O3(hematite) films have been deposited by radio frequency(RF) sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power and time as well as the sputter gas flow(argon),the microstructure and morphology of the film were optimized.It was found that the increment in the film thickness resulted in the loss of efficiency for solar water oxidation.The film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm-2at 1.23 VRHE.Addition of small amounts of O2to the sputter gas improved the photoactivity significantly.展开更多
Structure-engineered platinum-based nanoframes(NFs)at the atomic level can effectively improve the catalytic performance for fuel cells and other heterogeneous catalytic fields.We report herein,a microwave-assisted we...Structure-engineered platinum-based nanoframes(NFs)at the atomic level can effectively improve the catalytic performance for fuel cells and other heterogeneous catalytic fields.We report herein,a microwave-assisted wet-chemical method for the preparation of platinum-copper-cobalt NFs with tunable defect density and architecture,which exhibit enhanced activity and durability towards the electro-oxidation reactions of methanol(MOR)and formic acid(FAOR).By altering the reduction/capping agents and thus the nucleation/growth kinetics,trimetallic platinum-copper-cobalt hexapod NFs with different density high-index facets are achieved.Especially,the rough hexapod nanoframes(rh-NFs)exhibit excellent specific activities towards MOR and FAOR,7.25 and 5.20 times higher than those of benchmark Pt/C,respectively,along with prolonged durability.The excellent activities of the rh-NFs are assigned to a synergistic effect,including high density of defects and high-index facets,suitable d-band center,and open-framework structure.This synergistic working mechanism opens up a new way for enhancing their electrocatalytic performances by increasing defect density and high-index facets in open-framework platinum-based NFs.展开更多
The integration of gallium nitride(GaN)nanowire light-emitting diodes(nanoLEDs)on flexible substrates offers opportunities for applications beyond rigid solid-state lighting(e.g.,for wearable optoelectronics and benda...The integration of gallium nitride(GaN)nanowire light-emitting diodes(nanoLEDs)on flexible substrates offers opportunities for applications beyond rigid solid-state lighting(e.g.,for wearable optoelectronics and bendable inorganic displays).Here,we report on a fast physical transfer route based on femtosecond laser lift-off(fs-LLO)to realize wafer-scale top–down GaN nanoLED arrays on unconventional platforms.Combined with photolithography and hybrid etching processes,we successfully transferred GaN blue nanoLEDs from a full two-inch sapphire substrate onto a flexible copper(Cu)foil with a high nanowire density(~107 wires/cm2),transfer yield(~99.5%),and reproducibility.Various nanoanalytical measurements were conducted to evaluate the performance and limitations of the fs-LLO technique as well as to gain insights into physical material properties such as strain relaxation and assess the maturity of the transfer process.This work could enable the easy recycling of native growth substrates and inspire the development of large-scale hybrid GaN nanowire optoelectronic devices by solely employing standard epitaxial LED wafers(i.e.,customized LED wafers with additional embedded sacrificial materials and a complicated growth process are not required).展开更多
A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric(HClO_(4))and sulfuric(H_(2)SO_(4))electrolytes is obtained by comparing results whe...A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric(HClO_(4))and sulfuric(H_(2)SO_(4))electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions.By combining time-of-flight secondary ion mass spectrometry(ToF-SIMS)and in-situ atomic force microscopy(AFM),we provide a picture of the chemical species involved in the intercalation reaction.The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process,where the local morphology of the basal plane plays a crucial role.Solvated anions are mostly located within the first tens of nanometers of graphite,but electrolytes also diffuse inside the buried layers for hundreds of nanometers,the latter process is also aided by the presence of mesoscopic crystal defects.Residual material from the electrolyte solution was found localized in well-defined circular spots,which represent preferential interaction areas.Interestingly,blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite(HOPG)surface were found in the buried layers,confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers.展开更多
基金supported by the German Federal Ministry of Education and Research (BMBF) under contract#03SF0353A"H_2-NanoSolar"
文摘Ultra-thin α-Fe2O3(hematite) films have been deposited by radio frequency(RF) sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power and time as well as the sputter gas flow(argon),the microstructure and morphology of the film were optimized.It was found that the increment in the film thickness resulted in the loss of efficiency for solar water oxidation.The film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm-2at 1.23 VRHE.Addition of small amounts of O2to the sputter gas improved the photoactivity significantly.
基金This work was supported by the National Natural Science Foundation of China(Nos.21808079 and 21878121)Natural Science Foundation of Shandong Province(No.ZR2017BB029)+1 种基金China Postdoctoral Science Foundation(No.2017M610405)International Postdoctoral Exchange Fellowship Program Between Helmholtz-Zentrum Berlin für Materialien und Energie GmbH,OCPC and University of Jinan.
文摘Structure-engineered platinum-based nanoframes(NFs)at the atomic level can effectively improve the catalytic performance for fuel cells and other heterogeneous catalytic fields.We report herein,a microwave-assisted wet-chemical method for the preparation of platinum-copper-cobalt NFs with tunable defect density and architecture,which exhibit enhanced activity and durability towards the electro-oxidation reactions of methanol(MOR)and formic acid(FAOR).By altering the reduction/capping agents and thus the nucleation/growth kinetics,trimetallic platinum-copper-cobalt hexapod NFs with different density high-index facets are achieved.Especially,the rough hexapod nanoframes(rh-NFs)exhibit excellent specific activities towards MOR and FAOR,7.25 and 5.20 times higher than those of benchmark Pt/C,respectively,along with prolonged durability.The excellent activities of the rh-NFs are assigned to a synergistic effect,including high density of defects and high-index facets,suitable d-band center,and open-framework structure.This synergistic working mechanism opens up a new way for enhancing their electrocatalytic performances by increasing defect density and high-index facets in open-framework platinum-based NFs.
文摘The integration of gallium nitride(GaN)nanowire light-emitting diodes(nanoLEDs)on flexible substrates offers opportunities for applications beyond rigid solid-state lighting(e.g.,for wearable optoelectronics and bendable inorganic displays).Here,we report on a fast physical transfer route based on femtosecond laser lift-off(fs-LLO)to realize wafer-scale top–down GaN nanoLED arrays on unconventional platforms.Combined with photolithography and hybrid etching processes,we successfully transferred GaN blue nanoLEDs from a full two-inch sapphire substrate onto a flexible copper(Cu)foil with a high nanowire density(~107 wires/cm2),transfer yield(~99.5%),and reproducibility.Various nanoanalytical measurements were conducted to evaluate the performance and limitations of the fs-LLO technique as well as to gain insights into physical material properties such as strain relaxation and assess the maturity of the transfer process.This work could enable the easy recycling of native growth substrates and inspire the development of large-scale hybrid GaN nanowire optoelectronic devices by solely employing standard epitaxial LED wafers(i.e.,customized LED wafers with additional embedded sacrificial materials and a complicated growth process are not required).
基金the European Unions Horizon 2020 research and innovation program under Grant Agreement(No.688225)(Metro4-3D)the National Institute for Nuclear Physics in the framework of the CSN5 Call Project FIRE(Flexible Ionizing Organic Radiation Detectors)LASR3 Surface Analysis Laboratory Roma Tre gratefully acknowledges financial support from uFondazione Roma5(No.5229441F37).
文摘A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric(HClO_(4))and sulfuric(H_(2)SO_(4))electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions.By combining time-of-flight secondary ion mass spectrometry(ToF-SIMS)and in-situ atomic force microscopy(AFM),we provide a picture of the chemical species involved in the intercalation reaction.The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process,where the local morphology of the basal plane plays a crucial role.Solvated anions are mostly located within the first tens of nanometers of graphite,but electrolytes also diffuse inside the buried layers for hundreds of nanometers,the latter process is also aided by the presence of mesoscopic crystal defects.Residual material from the electrolyte solution was found localized in well-defined circular spots,which represent preferential interaction areas.Interestingly,blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite(HOPG)surface were found in the buried layers,confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers.