We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanow...We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.展开更多
The oxidation of a,b-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions ...The oxidation of a,b-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions are described. The rate of the oxidation reaction is faster and the yield is higher than that with conventional procedures.展开更多
The ever-growing market of wearable electronic devices has greatly stimulated the rapid development of flexible Zn-ion batteries(ZIBs).Manganese oxides are one of the most commonly used hosts for zinc ion accommodatio...The ever-growing market of wearable electronic devices has greatly stimulated the rapid development of flexible Zn-ion batteries(ZIBs).Manganese oxides are one of the most commonly used hosts for zinc ion accommodation and thus receive particular research interest for high-performance flexible ZIB constructions.In this review,a comprehensive summary of the recent development of flexible ZIBs with manganese oxides as cathode materials is presented.Apart from the brief introduction of flexible electronic devices and ZIBs,the charge storage mechanisms and crystal structures of various manganese oxides are summarized.Modifications of the cathode materials in terms of morphology,conductivity,structures,and flexibilities are illustrated in detail,together with the demonstration of structure-performance relationships and applications in flexible ZIBs.Finally,limitations to be overcome are indicated and the future work directions are proposed.展开更多
The presence of silver ions(Ag(I))in wastewater has a detrimental effect on living organisms.Removal of soluble silver,especially at low concentrations,is challenging.This paper presents the use ofβ-MnO2 particles as...The presence of silver ions(Ag(I))in wastewater has a detrimental effect on living organisms.Removal of soluble silver,especially at low concentrations,is challenging.This paper presents the use ofβ-MnO2 particles as a photocatalyst to remove Ag(I)ions selectively from aqueous solution at various pH levels.Inductively coupled plasma mass spectrometry(ICP-MS),X-ray diffraction(XRD),field emission electron microscope(FESEM),transmission electron microscopy(TEM),and X-ray photoelectron microscopy(XPS)were employed to determine the removal efficiency and to characterize the deposition of silver onto the surface ofβ-MnO2 particles.The optimum pH for the removal of Ag(I)ions was at pH 4 with 99%removal efficiency under 1 h of visible light irradiation.This phenomenon can be attributed to the electrostatic attraction betweenβ-MnO2 particles and Ag(I)ions as well as the suppression of electron–hole recombination in the presence of H+ions.展开更多
MnO 2 was prepared by column method from normal spinel LiMn 2O 4 with purity of 99.38%.The influence of LiMn 2O 4 grain size and acidity of leaching solution on the lithium leaching process was studied.The result...MnO 2 was prepared by column method from normal spinel LiMn 2O 4 with purity of 99.38%.The influence of LiMn 2O 4 grain size and acidity of leaching solution on the lithium leaching process was studied.The results show that the appropriate range of LiMn 2O 4 grain size was 60-160 meshes and the concentration of leaching solution HCl was 0.1 mol·L -1.The adsorption capacity Q of λ-MnO 2 for lithium increased with the increase of pH and changed markedly at pH 6.0-10.0.It was 3.80mmol/g at pH 12.0.The distribution coefficients K d of Li + and Na + were 3.406×10 4 and 2.300 respectively,and the separation coefficient α Li Na was 1.481×10 4 at pH 6.5.As a result,λ-MnO 2 is a high performance ion-sieve material for lithium ion.展开更多
A fundamental question in the oxygen reduction reaction(ORR)is how to rationally control the electrocatalytic selectivity for opening a four-electron reaction pathway.However,it still lacks direct experimental evidenc...A fundamental question in the oxygen reduction reaction(ORR)is how to rationally control the electrocatalytic selectivity for opening a four-electron reaction pathway.However,it still lacks direct experimental evidence to understand the reaction mechanism.This work unravels that Ag nanoparticles and carbonizing halloysite nanotubes(CHNTs)can trigger the construction of oxygen defects in the MnO_(2),which contribute to the generation of active sites.The Ag/MnO_(2)-CHNTs delivers a superior activity toward ORR with high onset potential,half-wave potential,diffusion-limited current density,long-term durability and methanol tolerance.More importantly,combined with density functional theory calculations,triggering manganese dioxide defects upon the introduction of Ag nanoparticles and CHNTs can alter the electrocatalytic pathway from a two-electron to a direct four-electron direction for ORR,which is the nature of enhanced ORR activity.Based on the analysis of the results,this finding points out a very effective approach for exploring catalysts with the improved performance and durability for ORR reaction.展开更多
基金financial supports provided by National Natural Science Foundation of China(Grant no.51104194 and 51104121)International S&T Cooperation Projects of Chongqing(CSTC 2013 gjhz90001)+1 种基金National Key laboratory of Fundamental Science of Micro/Nano-device and System Technology(2013MS06,Chongqing University)State Education Ministry and Fundamental Research Funds for the Central Universities(Project no.CDJZR14135501 and CDJZR13130036,Chongqing University,PR China)
文摘We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.
文摘The oxidation of a,b-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions are described. The rate of the oxidation reaction is faster and the yield is higher than that with conventional procedures.
基金The authors thank the financial support of this study received by the National Natural Science Foundation of China(21802173,21822509,and U1810110)Science and Technology Planning Project of Guangdong Province(2018A050506028)Youth Innovation Talents Project of Guangdong Universities(natural science)(2019KQNCX098).
文摘The ever-growing market of wearable electronic devices has greatly stimulated the rapid development of flexible Zn-ion batteries(ZIBs).Manganese oxides are one of the most commonly used hosts for zinc ion accommodation and thus receive particular research interest for high-performance flexible ZIB constructions.In this review,a comprehensive summary of the recent development of flexible ZIBs with manganese oxides as cathode materials is presented.Apart from the brief introduction of flexible electronic devices and ZIBs,the charge storage mechanisms and crystal structures of various manganese oxides are summarized.Modifications of the cathode materials in terms of morphology,conductivity,structures,and flexibilities are illustrated in detail,together with the demonstration of structure-performance relationships and applications in flexible ZIBs.Finally,limitations to be overcome are indicated and the future work directions are proposed.
基金This study was funded by Universiti Sains Malaysia, ResearchUniversity Grant (1001.PBAHAN.8014095). The authorsalso acknowledge the support from USM Fellowship.
文摘The presence of silver ions(Ag(I))in wastewater has a detrimental effect on living organisms.Removal of soluble silver,especially at low concentrations,is challenging.This paper presents the use ofβ-MnO2 particles as a photocatalyst to remove Ag(I)ions selectively from aqueous solution at various pH levels.Inductively coupled plasma mass spectrometry(ICP-MS),X-ray diffraction(XRD),field emission electron microscope(FESEM),transmission electron microscopy(TEM),and X-ray photoelectron microscopy(XPS)were employed to determine the removal efficiency and to characterize the deposition of silver onto the surface ofβ-MnO2 particles.The optimum pH for the removal of Ag(I)ions was at pH 4 with 99%removal efficiency under 1 h of visible light irradiation.This phenomenon can be attributed to the electrostatic attraction betweenβ-MnO2 particles and Ag(I)ions as well as the suppression of electron–hole recombination in the presence of H+ions.
基金theNationalNaturalScienceFoundationofChi na (No .5 9972 0 2 7)theNaturalScienceFoundationofHubeiProvince (No .2 0 0 2AB0 74) )
文摘MnO 2 was prepared by column method from normal spinel LiMn 2O 4 with purity of 99.38%.The influence of LiMn 2O 4 grain size and acidity of leaching solution on the lithium leaching process was studied.The results show that the appropriate range of LiMn 2O 4 grain size was 60-160 meshes and the concentration of leaching solution HCl was 0.1 mol·L -1.The adsorption capacity Q of λ-MnO 2 for lithium increased with the increase of pH and changed markedly at pH 6.0-10.0.It was 3.80mmol/g at pH 12.0.The distribution coefficients K d of Li + and Na + were 3.406×10 4 and 2.300 respectively,and the separation coefficient α Li Na was 1.481×10 4 at pH 6.5.As a result,λ-MnO 2 is a high performance ion-sieve material for lithium ion.
基金We thank the following funding agencies for supporting this work:the National Natural Science Foundation of China(grant no.21968020 and 22068026).
文摘A fundamental question in the oxygen reduction reaction(ORR)is how to rationally control the electrocatalytic selectivity for opening a four-electron reaction pathway.However,it still lacks direct experimental evidence to understand the reaction mechanism.This work unravels that Ag nanoparticles and carbonizing halloysite nanotubes(CHNTs)can trigger the construction of oxygen defects in the MnO_(2),which contribute to the generation of active sites.The Ag/MnO_(2)-CHNTs delivers a superior activity toward ORR with high onset potential,half-wave potential,diffusion-limited current density,long-term durability and methanol tolerance.More importantly,combined with density functional theory calculations,triggering manganese dioxide defects upon the introduction of Ag nanoparticles and CHNTs can alter the electrocatalytic pathway from a two-electron to a direct four-electron direction for ORR,which is the nature of enhanced ORR activity.Based on the analysis of the results,this finding points out a very effective approach for exploring catalysts with the improved performance and durability for ORR reaction.
