Plasma for Rapid Conversion Reactions and Surface Modification of Electrode Materials

Abstract

desirable to modify and functionalize the surface of electrode materials, such as by introducing defects, doping, and with high specific surface areas. For example, carbon materials doped with heteroatoms (N, S, P, etc.) have been extensively applied in energy storage and conversion devices. [9][10][11] In addition, commercialization of these energy devices requires not only good electrochemical performance, but also overall low cost. Therefore, for both synthesis and surface functionalization, it is meaningful to utilize cost-effective and efficient techniques.Plasma, as one of the four fundamental states of matter, consists of charged and neutral particles, in which the positive and negative ions are highly energetic and completely free to move. [12] Therefore ions in plasma show a higher chemical activity than diffusionlimited thermal reactions. [13] Plasma-assisted techniques are becoming powerful tools for nanoscale fabrication and modification, as plasmas provide a complex, reactive, and far-fromequilibrium chemical factory. Reactions that do not proceed easily at low temperatures have become possible with a short duration under a high-energy plasma ambient. Among the various types of plasmas, radio-frequency (RF) plasma systems are commonly utilized because of their energy efficiency, the short treatment duration, and the relatively low reactor-zone temperature. The plasma is produced by gas discharge initiated by RF electromagnetic fields. In this case, the electron temperature can be extremely high (10 4 −10 5 K), which makes the surface reaction very effective.The parameters of the plasma species, e.g., type of ionic particles and their densities, should be monitored and controlled. This is important if one wants to realize surface modification of electrode materials in an atomic depth. Different gas sources result in different plasma treatments, as they have different atomic, molecular, excited, and ionic species, with different densities, due to different dissociation and ionization energies. For example, nitride formation requires atomic nitrogen, which can be obtained from either nitrogen (N 2 ) gas or ammonia (NH 3 ) discharge plasma. The dissociation and ionization energies of ammonia are much lower than those of nitrogen molecules, and, hence, ammonia is preferred for plasma treatment, particularly in low-power plasma discharge. However, at moderate-or high-power plasma discharge, both are equally efficient in providing atomic nitrogen. NH 3 , however, is toxic and provides a wide variety of species in the plasma state, including N, N + , N 2 , H, H 2 , NH, and NH 2 , etc. The availability of NH 2 and H radicals in ammonia plasma may lead to amine Transition-metal compound (nitrides, carbides, phosphides, etc.) nanomaterials are under intensive research as potential advanced electrode materials in batteries, supercapacitors, and electrocatalytic water splitting. The radio-frequency plasma-assisted technique has emerged as a powerful tool in inducing nanoscale reactions, doping, defects, and nanos...

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…The plasma technology can quickly produce defects and doping on the surface of materials without damaging the nanostructure. Nowadays, low‐temperature plasma is widely used in the synthesis and surface modification of materials because of their high electron temperature, low gas temperature, and high energy properties . Wang's group used plasma technology to control the synthesis of various defects in crystalline materials to optimize the electronic structure and chemical properties of the surface .…”

“…Nowadays, lowtemperature plasma is widely used in the synthesis and surface modification of materials because of their high electron temperature, low gas temperature, and high energy properties. [44] Wang's group used plasma technology to control the synthesis of various defects in crystalline materials to optimize the electronic structure and chemical properties of the surface. [45] For instance, Tao et al produced abundant intrinsic defects on the surface of carbon materials by argon plasma etching, and transmission electron microscopy showed that many nanoscale holes and edge defects were generated by plasma treatment on graphene.…”

Single Atoms on Graphene for Energy Storage and Conversion

“…Apart from the heteroatoms, the introduction of vacancies on graphene would also be a novel approach for improving the stability of single atoms . Generally, high energy atom/ion bombardment or plasma sputtering is the common strategy to reconstruct the surface structure for generating vacancies or defects on graphene . For instance, the controllable formation of mono or divacancies on graphene was achieved by manipulating a focused electron beam at 80 kV .…”

Prereduction of Metal Oxides via Carbon Plasma Treatment for Efficient and Stable Electrocatalytic Hydrogen Evolution

“…Herein, we report a more efficient method to boost the HER catalytic activity of metal oxides with more stable performance via carbon plasma modification. Plasma treatment has been reported recently as a powerful approach for surface conversion reaction and modification of the electrode materials . In this work, we take NiMoO 4 nanowire arrays on carbon cloth as a case study.…”

“…Plasma treatment has been reported recently as a powerful approach for surface conversion reaction and modification of the electrode materials. [25][26][27][28][29][30] In this work, we take NiMoO 4 nanowire arrays on carbon cloth as a case study. As show in the Scheme 1, after the C-plasma treatment, active species of Ni 4 Mo nanoparticles are produced due to reduction of the NiMoO 4 .…”