Design of Hierarchal 3D Metal Oxide Structures for Water Oxidation and Purification

Abstract

Given their unique properties, tremendous progress is realized in the use of nanostructured materials for various applications. However, their incorporation and fabrication into prototypic devices remain challenging due to their limited ability to form hierarchical 3D structures through the use of large scale, low cost, and facile processes. Herein, this challenge is addressed and the growth of unique hierarchical structures is demonstrated by coating calcareous foraminiferal shells with metal oxide materials via simple and inexpensive processes conducted on a large scale. Foraminifera are highly diverse and abundant marine unicellular protists surrounded by large, ranging from 0.1 mm to more than 200 mm in size, identical porous, and complex hierarchical shells. In the present study, these hierarchal structures are investigated in electrochemical water oxidation reactions and tested in terms of their ability to purify water from inorganic (metal ions) contaminates. The remarkable performances of the prototype filters and catalysts developed here, among the best recorded values in both fields, are reported. These findings thus open new perspectives for catalytic and water purification applications.

Formation of Copper Oxide Nanotextures on Porous Calcium Carbonate Templates for Water Treatment

“…The color change (from turquoise to black or red-orange) and the obtained XRD pattern endorse the successful transformation of the orthorhombic Cu 2 Cl(OH) 3 to the respective copper oxide phase. According to a previous work [ 35 ], heating Sorites at high temperatures results in the formation of an additional phase (CaCO 3 ) alongside the rhombohedral Mg 0.1 Ca 0.9 CO 3 . Figure 4 c shows that after calcination, the obtained diffraction matches with rhombohedral Mg 0.1 Ca 0.9 CO 3 (JCPDS card no.…”

“…In addition to the net-like structure, the Sorites has internal tunnels that connect its holes. We believe that these tunnels may confine the reactants, which increases the collision probability of the reactant molecules, and in turn, improves the performance of the active material [ 34 , 35 , 36 ].…”

Calcareous Foraminiferal Shells as a Template for the Formation of Hierarchal Structures of Inorganic Nanomaterials

“…These structures were used as electrodes for water oxidation and as a filter for water purification. A superior performance was recorded in both fields …”

“…Nature is rich in microorganisms that possess unique hierarchal structures such as butterfly wings, bacteria, fungi, algae (especially the diatom), viruses, foraminifera, and others. These templates have attracted attention in science and industry because of their possible utilization for sensors, drug delivery, (photo)­catalysis, , supercapacitors, solar cells, optical devices, and others. − To date, there are various reports that describe a wide range of methods and techniques that use these templates to form 3D structures, such as hydrothermal, sonochemistry, vapor phase, sol–gel, gas/solid displacement, and others. − For example, bacterial pili were coated with metal oxides (Al 2 O 3 , TiO 2 , and ZnO) by atomic layer deposition . Au microtubules were formed by exposing the fungal microwires (taken from Aspergillus nidulans) to Au ions followed by reduction and then template removal by extraction in supercritical CO 2 .…”

Perspectives on applications of nanomaterials from shelled plankton

“…It can be considered challenging the recent fabrication of various 3D structures bearing nanostructures from foraminiferal shells as templates. [120] Interestingly, the bone regeneration property of a beta-tricalcium phosphate hydrothermally converted from foraminifera carbonate was investigated, underlining that these natural materials possess peculiar interconnected porous networks with adequate pore size distribution. These beta-tricalcium phosphate systems were able to be osteogenically active, and they exhibited full closure of the defect site induced in living samples.…”