Catalytic Nanotruss Structures Realized by Magnetic Self-Assembly in Pulsed Plasma

Abstract

Tunable nanostructures that feature a high surface area are firmly attached to a conducting substrate and can be fabricated efficiently over significant areas, which are of interest for a wide variety of applications in, for instance, energy storage and catalysis. We present a novel approach to fabricate Fe nanoparticles using a pulsed-plasma process and their subsequent guidance and self-organization into well-defined nanostructures on a substrate of choice by the use of an external magnetic field. A systematic analysis and study of the growth procedure demonstrate that nondesired nanoparticle agglomeration in the plasma phase is hindered by electrostatic repulsion, that a polydisperse nanoparticle distribution is a consequence of the magnetic collection, and that the formation of highly networked nanotruss structures is a direct result of the polydisperse nanoparticle distribution. The nanoparticles in the nanotruss are strongly connected, and their outer surfaces are covered with a 2 nm layer of iron oxide. A 10 μm thick nanotruss structure was grown on a lightweight, flexible and conducting carbon-paper substrate, which enabled the efficient production of H gas from water splitting at a low overpotential of 210 mV and at a current density of 10 mA/cm.

Impact of nanoparticle magnetization on the 3D formation of dual-phase Ni/NiO nanoparticle-based nanotrusses

“…Comparing the present results for pure Ni (condition i) with previously published results using Fe nanoparticles (Ekeroth et al 2018), similarities are observed with trusses highly oriented along the growth direction, i.e., Table 1 the magnetic field orientation of the external magnet. The nanotrusses, with lengths of up to 100 μm, are made up of nanowires that interlink.…”

“…The latter can be achieved, by using magnetic 1 nanoparticles combined with an applied magnetic field which allows the nanoparticles to self-assemble into nanowires or frameworks of nanowires-so-called nanotrusses. This can be achieved using magnetic particles in a liquid suspension (Kralj and Makovec 2015) or by direct generation and assembly of nanoparticles using plasma-based methods (Ekeroth et al 2018). The latter has the advantage of avoiding impurities, such as surface oxidization.…”

“…The latter has the advantage of avoiding impurities, such as surface oxidization. In a previous work, we have shown that Fe nanoparticles can be generated and assembled, onto a variety of substrates, into long (> 100 μm) nanotrusses through a plasma where the particles are generated followed by magnetic collection (Ekeroth et al 2018). The low packing density of these trusses makes the material suitable for electrocatalysts since reactants can reach a high fraction of the exposed surface.…”

Rational Design of Nanoarray Architectures for Electrocatalytic Water Splitting

“…Plasma‐induced approach is a versatile technique for rapid and large‐scale treatment of various materials by use of plasma gases under the appropriate regulation of plasma frequency and temperature . However, the need of frequency and temperature and high cost of plasma as the disadvantages are always required in this plasma‐induced process.…”

“…To develop efficient hydrogen evolution reaction catalysts, surface reorganization of CoP nanowire arrays grown on carbon cloth was conducted by oxygen plasma engraving treatment, triggering moderate CoO x species formation on the surface of CoP nanowires and thus enhancing alkaline HER performance . Fe nanostructures on a substrate with magnetic self‐assembly were produced through a pulsed plasma process by using an external magnetic field, enabling the efficient H 2 production from water splitting . Cu 2 S nanosheet arrays on Cu foam were also synthesized by a facile iodine dielectric barrier discharge plasma and an anion‐exchange reaction, presenting prominent electrocatalytic activity and persistent stability .…”