Synthesis of multifunctional hybrid materials via layered double hydroxides mediated route
Date of Issue2017-05-05
School of Materials Science and Engineering
Hybrid materials in general could be classified into three categories : (i) mixed metal oxides (MMO), (ii) MMO with noble metal hybrid, and (iii) MMO with nanocarbon hybrid. Ln this research work, layered double hydroxides (LDH) mediated route is utilized to synthesize the three types of multifunctional hybrid materials . Studies will focus on understanding how the LDH mediated route lead to the intimately mixed morphology and strong interfacial interaction of the hybrid materials . The impact of these features on the functional property improvement is discussed thoroughly. This research begins with a systematic investigation on the properties of ZnGaFe ternary MMO prepared via LDH mediated route , and non-LDH route (solid state reaction method) is used as a comparison. Detailed analysis reveals that the MMO derived from LDH mediated approach not only has uniform and well mixed morphology, but also possesses strong metal to metal interactions. All of these characteristic properties are reflected in the study of photocatalytic reactions. To synthesis MMO-noble metal hybrid material , the noble metal ion ([AuCI4D intercalated ZnFe LDH is used as a solid state molecular precursor. Intimately mixed ZnFe MMO with uniformly decorated Au nanoparticles is obtained after low temperature calcination. In this work, the evolution of direct intercalated LDH structure is discussed in details. The intra-layer merging mechanism is proposed for the MMO growth during heat treatment. The morphology created is intimately mixed as compared with that of MMO obtained from inter-layer merging mechanism . The intimate interface could lead to favorable band alignment and excellent synergistic interactions for photocatalytic reactions . The LDH mediated route for synthesis of MMO-CNT hybrid material is also attempted . NiFe LDH nano-plates were firstly deposited on CNT through electrostatic force . With controlled calcination process , NiFe MMO and CNT hybrid material is obtained. The nano sized NiFe MMO obtained from the LDH precursor is intimately mixed, which ensures the strong interaction between Ni and Fe in MMO. More importantly, the hybrid is featured with a unique in-grown structure which is formed due to the carbon reduction reaction during calcination. Instead of coupling through organic ligand or electrostatic force, the in-grown structure results to strong chemical bonding between MMO and CNT, The strong coupling is very favorable for the charge transfer process, and hence significantly improved the electrochemical property. This thesis concludes the outcomes and findings from the three connected works. Some extended works that could benefit from the concept of LDH mediated synthesis route are proposed.