Assembly Of Cuni Bimetallic Transition Metal Layered Double Hydroxide Based Nanosheets Array-like Hybrides For Highly Efficient Reduction Of Nitrophenol

In order to enhance the catalytic activity of hierarchical Cu-based catalysts and achieve highly efficient recyclable green catalysts upon Cu-based bimetallic metals,a series of Ni functionalized Cu-based bimetallic transition metal layered double hydroxide(LDH)nanosheets array-like hybrids LDH/rGO(rGO:reduced Graphene Oxide)and LDH/NF(NF:nickel foam)are assembled using one-step coprecipitation method and hydrothermal method,respectively.Their catalytic activities for the reduction of 4-nitrophenol and structure-performance relationship are systematically studied.The thesis focuses on::1)A series of hierarchically structured CuxNi3-xAl-LDH/rGO(x =0.5,1.0,1.5)bimetallic transition metals LDH nanosheets array-like hybrid catalysts are assembled through a citric acid-assistanted one-step copercipitation method upon atomically dispersed metal cations on LDH layers and the modification of Cu by metal Ni.The nanohybrids CuxNi3-xAl-LDH/rGO are assembled by ultrathin LDH nanosheets(～80.0 x 7.8 nm)with the ab-plane vertical to the surface of rGO in both sides,and LDH nanosheets are consisting of primary hexagonal plates with Scherrer dimension D003(3.27-3.77 nm)and D110(7.85-7.93 nm)resulting in larger surface area(150.03-151.82 m2 g-1)of the hybrids.Metallic ions Cu2+ and Ni2+ are highly dispersed on the LDH layer,and the sample Cu1Ni2Al-LDH/rGO have the highest electron cloud density arround Cu2+and Ni2+ core levels.2)The catalytic reduction of 4-NP under room temperature show that CuxNi3-xAl-LDH/rGO nanohybrids have obviously higher activity than pure CuNiAl-LDH.The Cu1Ni2Al-LDH/rGO shows the highest catalytic activity(kapp = 34.37 × 10-3 s-1,knor = 13350 s-1 g-1,TOF = 197.5 h-1),which is higher than previously reported CuNi bimetallic catalysts.The activities of CuxNi3-xAl-LDH/rGO nanohybrids are higher than the binary hybrids Cu2Al-LDH/rGO and Ni3Al-LDH/rGO,implying the dopation of Ni greatly enhances the catalytic activity of Cu.The excellent catalytic activities of these nanosheets array-like hybrids can be attributed to 1)the highly dispersed and small-sized active Cu20 phase(～5.2 nm)formed by fast in situ reduction of atomically dispersed Cu2+ in LDH layers as well as Cu20-LDH-rGO three-phase synergistic effect,2)the improving effect of Ni,and 3)increased adsorption capacity for reactants via π-π stacking.The catalysts show excellent recyclable performance and almost no obvious decrease in activity after 10 runs.Moreover,Cu1Ni2Al-LDH/rGO has excellent universal catalytic activity in the reduction of diverse nitroarene and degradation of several anionic azo dyes.The catalysts could high-efficiently catalyse the reduction of 4-NP and methyl orange in simulated fix-bed system under high flow rate(～8.0 mL min-1)with a TOF of 6.048 h-1,implying attracted potential in waste water remediation.3)Cu1.5Ni1.5Al-LDH/NF nanosheets array-like composite catalyst with LDH nanoplates uniformly dispersed and vertically grown on the surface of nickel foam skeleton is achieved by coprecipitation-hydrothermal route.The obtained nanocomposite exhibits excellent activity for catalytic reduction of 4-NP(kapp = 7.12 min-1)and outstanding recycling stability and as possible reaction device with convenient operation for reaction and recycle showing potential application in waste water remediation.