Note: Rapid reduction of graphene oxide paper by glow discharge plasma

The application of plasma technology for the preparation of supercapacitor electrode materials

With the rapidly growing demand for clean energy and energy interconnection, there is an urgent need for rapid and high-capacity energy storage technologies to realize large-scale energy storage, transfer energy, and establish the energy internet. Supercapacitors, which have advantages such as high specific capacitance, fast charging and discharging rates, and long cycle lifetimes, are being widely used in electric vehicles, information technology, aerospace, and other fields. The performance of supercapacitors is crucially dependent on electrode materials. These can be categorized into electric double-layer capacitors and pseudocapacitors, primarily made from carbon and transition metal oxides, respectively. However, effectively monitoring the physicochemical properties of electrode materials during preparation and processing is challenging, which limits the improvement of supercapacitors' performance. Plasma materials preparation technology can effectively affect the materials preparation processing by energetic electrons, ions, free radicals, and multiple effects in plasma, which are easily manipulated by operation parameters. Therefore, plasma material preparation technology is considered a promising method to precisely monitor the physicochemical and electrochemical properties of energy storage materials and has been widely studied. This paper provides an overview of plasma materials preparation mechanisms, and details of the plasma technology application in the preparation of transition metal hybrids, carbon, and composite electrode materials, as well as a comparison with traditional methods. In conclusion, the advantages, challenges, and research directions of plasma materials preparation technology in the field of electrode materials preparation are summarized.

Plasma Assisted Reduction of Graphene Oxide Films

The past decade has seen enormous efforts in the investigation and development of reduced graphene oxide (GO) and its applications. Reduced graphene oxide (rGO) derived from GO is known to have relatively inferior electronic characteristics when compared to pristine graphene. Yet, it has its significance attributed to high-yield production from inexpensive graphite, ease of fabrication with solution processing, and thus a high potential for large-scale applications and commercialization. Amongst several available approaches for GO reduction, the mature use of plasma technologies is noteworthy. Plasma technologies credited with unique merits are well established in the field of nanotechnology and find applications across several fields. The use of plasma techniques for GO development could speed up the pathway to commercialization. In this report, we review the state-of-the-art status of plasma techniques used for the reduction of GO-films. The strength of various techniques is highlighted with a summary of the main findings in the literature. An analysis is included through the prism of chemistry and plasma physics.

Electrically Conductive, Reduced Graphene Oxide Structures Fabricated by Inkjet Printing and Low Temperature Plasma Reduction

Here, an environmentally-friendly and scalable process is reported to synthesize reduced graphene oxide (RGO) thin films for printed electronics applications. The films are produced by inkjet printing GO flakes dispersed binder-free in aqueous solutions followed by treatment with a nonthermal, radio-frequency (RF) plasma containing only argon (Ar) gas. The plasma process is found to heat the substrate to temperatures no greater than 138 °C, enabling RGO to be printed directly on a wide range of temperature-sensitive substrate materials including photo paper. Unlike other low-temperature methods such as electrochemical reduction, plasma reduction is friendly to moisture absorbent materials. Moreover, the plasma treatment can be performed on nonconducting substrates, eliminating the need for film transfer. From an applications perspective, the printed, plasma-reduced RGO exhibits excellent electrical, mechanical, and electrochemical properties. As a technology demonstrator, the working electrodes of hydrogen peroxide (H₂O₂) sensors fabricated from plasma-reduced GO show a sensitivity of 277 ± 80 μA mm^-1 cm^-2, which is comparable to RGO working electrodes made by electrochemical reduction.