Rechargeable zinc-air batteries(ZABs)are a promising energy conversion device,which rely critically on electrocatalysts to accelerate their rate-determining reactions such as oxygen reduction(ORR)and oxygen evolution ...Rechargeable zinc-air batteries(ZABs)are a promising energy conversion device,which rely critically on electrocatalysts to accelerate their rate-determining reactions such as oxygen reduction(ORR)and oxygen evolution reactions(OER).Herein,we fabricate a range of bifunctional M-N-C(metal-nitrogen-carbon)catalysts containing M-Nx coordination sites and M/MxC nanoparticles(M=Co,Fe,and Cu)using a new class ofγ-cyclodextrin(CD)based metal-organic framework as the precursor.With the two types of active sites interacting with each other in the catalysts,the obtained Fe@C-FeNC and Co@C-CoNC display superior alkaline ORR activity in terms of low half-wave(E1/2)potential(~0.917 and 0.906 V,respectively),which are higher than Cu@C-CuNC(~0.829 V)and the commercial Pt/C(~0.861 V).As a bifunctional electrocatalyst,the Co@C-CoNC exhibits the best performance,showing a bifunctional ORR/OER overpotential(ΔE)of~0.732 V,which is much lower than that of Fe@C-FeNC(~0.831 V)and Cu@C-CuNC(~1.411 V),as well as most of the robust bifunctional electrocatalysts reported to date.Synchrotron X-ray absorption spectroscopy and density functional theory simulations reveal that the strong electronic correlation between metallic Co nanoparticles and the atomic Co-N4 sites in the Co@C-CoNC catalyst can increase the d-electron density near the Fermi level and thus effectively optimize the adsorption/desorption of intermediates in ORR/OER,resulting in an enhanced bifunctional electrocatalytic performance.The Co@C-CoNC-based rechargeable ZAB exhibited a maximum power density of 162.80 mW cm^(−2) at 270.30 mA cm^(−2),higher than the combination of commercial Pt/C+RuO2(~158.90 mW cm^(−2) at 265.80 mA cm^(−2))catalysts.During the galvanostatic discharge at 10 mA cm^(−2),the ZAB delivered an almost stable discharge voltage of 1.2 V for~140 h,signifying the virtue of excellent bifunctional ORR/OER electrocatalytic activity.展开更多
A new ZnS/CdS heterojunction is constructed through the direct sulfurization of a metal ions exchanged Zn/Cd-MOF precursor(MOF=metal-organic framework material).The composition,structure,morphology,photoabsorption and...A new ZnS/CdS heterojunction is constructed through the direct sulfurization of a metal ions exchanged Zn/Cd-MOF precursor(MOF=metal-organic framework material).The composition,structure,morphology,photoabsorption and photoelectric performance of the ZnS/CdS are characterized by powder X-ray diffraction(PXRD),scanning electron microscope(SEM),transmission electron microscope(TEM),diffuse reflection spectrum(DRS),photoelectric current(PEC),electrochemical impedance spectroscopy(El S)and photoluminescence(PL)technologies.Since the metal ions are highly orderly separated by the organic ligands and the inherent porosity of the Zn/Cd-MOF,the as-synthesized ZnS/CdS possesses a large surface area and intimate contact at the heterogeneous interface with uniform ZnS/CdS nanoparticles.The photocatalytic hydrogen evolution activity of the ZnS/CdS is investigated under visible light irradiation(A^420 nm).It exhibits enhanced photocatalytic performance that the optimal ZnS/CdS achieves a maximum average hydrogen production rate of 2348μmol·h^-1 g^-1.A possible electron transfer mechanism is therefore proposed by the analyses of the Mott-Schottky plots.展开更多
基金supported by the Shenzhen Government’s Plan of Science and Technology(JCYJ20190808121407676 and 20200813142301001)National Natural Science Foundation of China(22178223 and 22262010)+1 种基金Guangxi Science and Technology Fund for Distinguished High-Talent Introduction Program(No.RZ2200002233AC22035091).
文摘Rechargeable zinc-air batteries(ZABs)are a promising energy conversion device,which rely critically on electrocatalysts to accelerate their rate-determining reactions such as oxygen reduction(ORR)and oxygen evolution reactions(OER).Herein,we fabricate a range of bifunctional M-N-C(metal-nitrogen-carbon)catalysts containing M-Nx coordination sites and M/MxC nanoparticles(M=Co,Fe,and Cu)using a new class ofγ-cyclodextrin(CD)based metal-organic framework as the precursor.With the two types of active sites interacting with each other in the catalysts,the obtained Fe@C-FeNC and Co@C-CoNC display superior alkaline ORR activity in terms of low half-wave(E1/2)potential(~0.917 and 0.906 V,respectively),which are higher than Cu@C-CuNC(~0.829 V)and the commercial Pt/C(~0.861 V).As a bifunctional electrocatalyst,the Co@C-CoNC exhibits the best performance,showing a bifunctional ORR/OER overpotential(ΔE)of~0.732 V,which is much lower than that of Fe@C-FeNC(~0.831 V)and Cu@C-CuNC(~1.411 V),as well as most of the robust bifunctional electrocatalysts reported to date.Synchrotron X-ray absorption spectroscopy and density functional theory simulations reveal that the strong electronic correlation between metallic Co nanoparticles and the atomic Co-N4 sites in the Co@C-CoNC catalyst can increase the d-electron density near the Fermi level and thus effectively optimize the adsorption/desorption of intermediates in ORR/OER,resulting in an enhanced bifunctional electrocatalytic performance.The Co@C-CoNC-based rechargeable ZAB exhibited a maximum power density of 162.80 mW cm^(−2) at 270.30 mA cm^(−2),higher than the combination of commercial Pt/C+RuO2(~158.90 mW cm^(−2) at 265.80 mA cm^(−2))catalysts.During the galvanostatic discharge at 10 mA cm^(−2),the ZAB delivered an almost stable discharge voltage of 1.2 V for~140 h,signifying the virtue of excellent bifunctional ORR/OER electrocatalytic activity.
基金Supported by the National Natural Science Foundation of China(Nos.21661020,21961021).
文摘A new ZnS/CdS heterojunction is constructed through the direct sulfurization of a metal ions exchanged Zn/Cd-MOF precursor(MOF=metal-organic framework material).The composition,structure,morphology,photoabsorption and photoelectric performance of the ZnS/CdS are characterized by powder X-ray diffraction(PXRD),scanning electron microscope(SEM),transmission electron microscope(TEM),diffuse reflection spectrum(DRS),photoelectric current(PEC),electrochemical impedance spectroscopy(El S)and photoluminescence(PL)technologies.Since the metal ions are highly orderly separated by the organic ligands and the inherent porosity of the Zn/Cd-MOF,the as-synthesized ZnS/CdS possesses a large surface area and intimate contact at the heterogeneous interface with uniform ZnS/CdS nanoparticles.The photocatalytic hydrogen evolution activity of the ZnS/CdS is investigated under visible light irradiation(A^420 nm).It exhibits enhanced photocatalytic performance that the optimal ZnS/CdS achieves a maximum average hydrogen production rate of 2348μmol·h^-1 g^-1.A possible electron transfer mechanism is therefore proposed by the analyses of the Mott-Schottky plots.
