Magnetoelectrically Driven Catalytic Degradation of Organics

Abstract

Here, we report the catalytic degradation of organic compounds by exploiting the magnetoelectric (ME) nature of cobalt ferrite-bismuth ferrite (CFO-BFO) core-shell nanoparticles. The combination of magnetostrictive CFO with the multiferroic BFO gives rise to a magnetoelectric engine that purifies water under wireless magnetic fields via advanced oxidation processes, without involvement of any sacrificial molecules or co-catalysts.Magnetostrictive CoFe2O4 nanoparticles are fabricated using hydrothermal synthesis, followed by sol-gel synthesis to create the multiferroic BiFeO3 shell. We perform theoretical modeling to study the magnetic field induced polarization on the surface of magnetoelectric nanoparticles. The results obtained from these simulations are consistent with the experimental findings of the piezo-force microscopy analysis, where we observe changes in the piezoresponse of the nanoparticles under magnetic fields. Next, we investigate the magnetoelectric effect induced catalytic degradation of organic pollutants under AC magnetic fields and obtained 97% removal efficiency for synthetic dyes and over 85% removal efficiency for routinely used pharmaceuticals. Additionally, we perform trapping experiments to elucidate the mechanism behind the magnetic field induced catalytic degradation of organic pollutants by using scavengers for each of the reactive species. Our results indicate that hydroxyl and superoxide radicals are the main reactive species in the magnetoelectrically induced catalytic degradation of organic compounds. 3Magnetic nanostructures have been widely used as magnetically recoverable catalysts or as carriers for catalytic materials. [1] While magnetic nanomaterials have found widespread applications in tuning catalytic processes, a majority of the employed strategies focus on their motion to enhance the reagents' mass transport. [2] A next level of control can be achieved by forcing such magnetic nanoparticles to interact [3] or, alternatively, by coupling them to catalysts to enhance the reaction performance. [4] In previous investigations, magnetic fields only support the catalytic chemical conversion but never act as the ultimate trigger. Direct control of causality is fundamental in realistic scenarios, where the choice of the precise moment of actuation is critical. In this direction, magnetically induced heating has been demonstrated to initiate chemical catalysis on demand. [5] Here, we demonstrate a localized trigger for catalytic reactions via the direct magnetoelectric (ME) effect on the surface of multiferroic nanoparticles. Our ME nanocatalysis is able to decompose organic contaminants, such as dyes and various pharmaceuticals, without the involvement of any sacrificial molecules or co-catalysts. Our experiments revealed a rich interdependence between the applied magnetic field parameters and the reaction speed, which significantly improves the performance of catalytic reactions for environmental remediation.Organic pollutants such as pharmaceuticals, pesticides and industr...

Multi‐Component Mesocrystalline Nanoparticles with Enhanced Photocatalytic Activity

“…[ 49 ] The highly reactive OH radicals produced in the above processes effectively decompose methylene blue dye, a model organic pollutant molecule, into unit molecules such as CO 2 and H 2 O. [ 50–52 ]…”

“…[49] The highly reactive OH radicals produced in the above processes effectively decompose methylene blue dye, a model organic pollutant molecule, into unit molecules such as CO 2 and H 2 O. [50][51][52] The photocatalytic performances of mesocrystalline nanoparticles were measured by the degradation of methylene blue (MB) solution under visible light in the presence of H 2 O 2 . Detailed conditions of photo-Fenton-like catalytic processes such as the amount of H 2 O 2 , dye concentration, and pH were set according to previous studies ( Figure S13, Supporting Information).…”

Multiferroics beyond electric-field control of magnetism

“…An environmentally relevant application of photocatalysis is water purification through the catalytic degradation of high molecular weight organic molecules such as contaminant dyes into smaller molecules such as CO 2 or H 2 O. BiFeO 3 nanosheets, nanowires and nanoparticles have been demonstrated to photo-degrade large organic dyes such as methyl orange [44] and rhodamine B [45] in the presence of sunlight, with mechanical vibrations increasing the efficiency likely due to the internal piezoelectric fields' promoting charge separation [46]. Intriguingly, magnetoelectric cobalt ferrite / bismuth ferrite coreshell nanoparticles were shown to catalyze the breakdown of synthetic dyes and pharmaceuticals in the presence of an AC magnetic field, even without sunlight [47], highlighting a need for improved understanding of the inter-play between applied fields, the surface electronic structure, the defect chemistry and microstructure, and the environment. A helfpul review of synthesis methods for BiFeO 3 nanoparticles, and the factors that affect their efficiency in environmental mediation, can be found in Ref.…”

Enhanced Photocatalysis by Synergistic Piezotronic Effect and Exciton–Plasmon Interaction Based on (Ag‐Ag2S)/BaTiO3 Heterostructures

“…Industrial wastewater is inevitable with the rapid development of modern society, especially the dyes contaminants that have severely polluted the freshwater resources. [1][2][3][4][5][6][7] Photocatalysis provides an effective strategy to the decomposi tion of these contaminants in low cost and large scale. [4,8,9] Conventional hetero structured photocatalysts (e.g., Au/ TiO 2 , Ag 2 O/TiO 2 , and CuO/BiVO 4 ) have gained remarkable achievements due to the broadband light absorption and improved separation efficacy of photon generated electronhole pairs.…”