sintesi e applicazioni di architetture 3D multifunzionali a base di carbonio

In this thesis, I have been focusing on the investigation of 3D graphene aerogel nanoarchitectures to be used as advanced supports for heterogeneous catalysis. The combination of 3D graphene nanostructures with noble-metal-free electrocatalysts materials can produce systems with a large surface area, but also provide an architecture with tailored porosity, offering an efficient interaction with the electrolyte, which requires a combination of micro- and meso-porosity. Moreover, the crosslink within the 3D graphene network can avert the degradation of the catalytic performance caused by the re-stacking of graphene sheets or the coarsening of the hosted active phases. The thesis is divided in four main chapters. Chapter 1 is an introduction and summary of the preparation and application of 3D graphene aerogel composite materials, and explains its application scope and collocation within the broader context of modern catalysis. In addition, it also provides some basic information about the materials studied and the basic principles behind their design. Moreover, GOAMs with well-controlled morphologies and highly ordered structures will be introduced, display a quite unique center-diverging microchannel dandelion-like structure. In Chapter 2, we investigated the preparation of innovative hybrid electrocatalysts coupling TMDCs nanosheets with GOAMs (TMDC/GOAM) by electrospray and freeze casting techniques. The aim is to prove that it is possible to integrate into the GOAM graphene network the functional properties of active electrocatalysts without altering the microchannel central divergence morphology. The procedure of incorporation has been optimized using exfoliated MoSe2, and subsequently it was successfully extended to other exfoliated TMDCs, i.e., MoS2, WS2 and WSe2. The aim was to create a hybrid material where electronic contacts among the two pristine materials are established in a 3D architecture, to test any improvement in the HER activity while maintaining accessible the TMDC catalytic sites. The final materials were used to prepare an electrode suitable for the HER characterization. In Chapter 3, we made a step forward and propose a synthesis strategy to control not only the morphology of the nanocomposite, but also the chemistry of the active phase. To achieve this goal, we envisaged a fully bottom-up approach for preparing the MoS2 phase decorating the 3D GOAM scaffold, which is based on a molecular precursor, e.g. ATM, ((NH4)2MoS4). The advantages of this approach to prepare the hybrid MoS2/prGOAM materials are: i) fine and homogeneous dispersion of MoS2 on the graphenic support, ii) higher scalability of the preparation procedure, and shorter preparation time since there is no need to prepare the TMDC by a lengthy and expensive exfoliation procedure, iii) possibility to introduce a large variety of dopants into the MoS2 moiety. The resulting materials with both tailored morphology and chemistry demonstrated to be outstanding catalyst for the HER, superior to previous top-down MoS2 (in Chapter 2) based catalysts. In Chapter 4, in order to study the general applicability of our materials, we have studied the development of a heterostructure constructed by CoAl-LDH NR supported on GOAMs as a highly efficient electrocatalyst for water oxidation. The presence of negatively charged GOAMs can play an import role in supporting and dispersing positively charged CoAl-LDH NR. The as-prepared electrocatalyst, denoted as CoAl-LDH NR/GOAMs, inherits the special centre-diverging microchannel 3D structure from GOAMs, with numerous CoAl-LDH NR decorating quite homogeneously the GO surface. As a result, the CoAl-LDH NR/prGOAMs exhibit a remarkable electrocatalytic activity in the OER. The general conclusions and perspectives of this work are summarized in Chapter 5.