Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily a...Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.展开更多
By stepwise adding of reducer N2H4.H2O, cuprous oxide （Cu2O） nanoparticles （NPs） with adjustable structures were synthe- sized. The features of Cu2O NPs were characterized by XRD, TEM and UV-Vis absorption spectra...By stepwise adding of reducer N2H4.H2O, cuprous oxide （Cu2O） nanoparticles （NPs） with adjustable structures were synthe- sized. The features of Cu2O NPs were characterized by XRD, TEM and UV-Vis absorption spectra. When the reducer was added into the reactant system at one time, the sizes of the Cu2O NPs are in the range of 120-140 nm. Most Cu2O NPs are sol- id spheres. As the reducer was divided into two equal parts and stepwisely added, almost all the NPs are hollow spheres with good size （150-170 nm） distribution and dispersity. But when the reducer was divided into three or four equal parts and stepwisely added, the NPs are hollow spheres, core-shell structures or solid spheres, and the sizes distribution of the products is deteriorated. The effect of sodium hydrate （NaOH） was also probed. Addition of NaOH speeded up the nucleation and growth processes of Cu2O NPs. With the alkalinity increase, the shells of the hollow spheres become compact and the thicknesses of the shells increase, but the size distribution of the NPs is deteriorated. The absorption spectra of the CuzO NPs are tunable. With the shell thicknesses increase, the absorption peaks have red shifts. An inside-outside growth model of Cu2O NPs was proposed to explain the results. The Cu2O single crystalline grains grow not only in the reactant solution, but also inside of the hollow nanospheres. The new Cu2O nanocrystallines can not only aggregate onto the shells of the nano hollow spheres, but also inside and outside of the hollow spheres, which leads to increasing the shell thicknesses of the hollow spheres, forming core-shell structures or small solid spheres of Cu2O NPs, respectively.展开更多
文摘Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.
基金supported by the National Natural Science Foundation of China(Grant Nos.41172110 and 61107090)Shandong Provincial Natural Science Foundation(Grant No.ZR2011BZ007)
文摘By stepwise adding of reducer N2H4.H2O, cuprous oxide （Cu2O） nanoparticles （NPs） with adjustable structures were synthe- sized. The features of Cu2O NPs were characterized by XRD, TEM and UV-Vis absorption spectra. When the reducer was added into the reactant system at one time, the sizes of the Cu2O NPs are in the range of 120-140 nm. Most Cu2O NPs are sol- id spheres. As the reducer was divided into two equal parts and stepwisely added, almost all the NPs are hollow spheres with good size （150-170 nm） distribution and dispersity. But when the reducer was divided into three or four equal parts and stepwisely added, the NPs are hollow spheres, core-shell structures or solid spheres, and the sizes distribution of the products is deteriorated. The effect of sodium hydrate （NaOH） was also probed. Addition of NaOH speeded up the nucleation and growth processes of Cu2O NPs. With the alkalinity increase, the shells of the hollow spheres become compact and the thicknesses of the shells increase, but the size distribution of the NPs is deteriorated. The absorption spectra of the CuzO NPs are tunable. With the shell thicknesses increase, the absorption peaks have red shifts. An inside-outside growth model of Cu2O NPs was proposed to explain the results. The Cu2O single crystalline grains grow not only in the reactant solution, but also inside of the hollow nanospheres. The new Cu2O nanocrystallines can not only aggregate onto the shells of the nano hollow spheres, but also inside and outside of the hollow spheres, which leads to increasing the shell thicknesses of the hollow spheres, forming core-shell structures or small solid spheres of Cu2O NPs, respectively.
