Carbon Nanotubes Deposited on Mordenite Zeolite/NiAl-Layered Double Hydroxide Composites as Electrocatalysts for 2,5-Furandicarboxylic Acid Production from 5-Hydroxymethylfurfural

The nanostructured free-standing NiAl-MOR-CNTs electrocatalystscontaining carbon nanotubes (CNTs) deposited on mordenite (MOR) zeolite/NiAl-layereddouble hydroxide (NiAl-LDH) have been successfully fabricated. Initially,the core-shell NiAl-LDH-MOR with hierarchical structures was observedvia an aqueous miscible organic solvent treatment process to depositnanosized NiAl-LDH homogeneously on a zeolite surface. The synthesizedNiAl-LDH-MOR composites were calcined to produce highly dispersedmetal oxides catalyzing the CNTs formation via chemical vapor depositionusing bioethanol as a feedstock, eventually producing the NiAl-MOR-CNTscomposites. To illustrate the beneficial aspect of the prepared composite,they were mixed with Nafion as a binder and pressed into circularpellets used as free-standing electrodes for electrochemical oxidationof 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA),an important renewable monomer of bioplastic. The prepared free-standingelectrodes exhibited an excellent catalytic performance of 100% conversionof HMF with a high selectivity of FDCA up to 92% under ambient conditions.Moreover, the synthesized electrocatalysts can be recycled even afterseveral consecutive cycles without any loss of catalytic activity,confirming a high stability of the synthesized electrodes. This workillustrates the design of electrocatalysts by using conductive CNTsgrown on highly dispersed metal active sites on zeolite/LDH compositeswithout using commercial conductive supports such as nickel foam orcarbon fiber paper.