The manganese oxide graphene oxide (Mn ₃ O ₄ /rGO) composite heterojunction with copper oxide is useful for the production of an electrochemical supercapacitor. The graphene oxide and manganese oxide composite have been synthesized by adopting a method of co-precipitation. The composite of Mn ₃ O ₄ /rGO was synthesized with different concentrations of Mn ₃ O ₄ and rGO. The structural, morphological, electrochemical and supercapacitive properties of Mn ₃ O ₄ /rGO composite have been examined. The electrochemical and supercapacitive properties have been studied with regard to different substrates. The Mn ₃ O ₄ /rGO composite was deposited on different substrates such as steel, copper and brass. The CuO/Mn ₃ O ₄ /rGO shows relatively better specific capacitance (856 F g ⁻¹ ) and better stability (82% retention after 2000 cycles) than other substrates used. The present work describes the development of cost-effective and high-performance CuO/Mn ₃ O ₄ /rGO-based nanomaterials for supercapacitors. The CuO/Mn ₃ O ₄ /rGO composite can be used as a flexible supercapacitor device.

Wrinkles are observed commonly in CVD (chemical vapor deposition)-grown graphene on Cu and hydrogen etching is of significant interest to understand the growth details, as well as a practical tool for fabricating functional graphene nanostructures. Here, we demonstrate a special hydrogen etching phenomenon of wrinkled graphene domains. We investigated the wrinkling of graphene domains under fast cooling conditions and the results indicated that wrinkles in the monolayer area formed more easily compared to the multilayer area (≥two layers), and the boundary of the multilayer area tended to be a high density wrinkle zone in those graphene domains, with a small portion of multilayer area in the center. Due to the site-selective adsorption of atomic hydrogen on wrinkled regions, the boundary of the multilayer area became a new initial point for the etching process, aside from the domain edge and random defect sites, as reported before, leading to the separation of the monolayer and multilayer area over time. A schematic model was drawn to illustrate how the etching of wrinkled graphene was generated and propagated. This work may provide valuable guidance for the design and growth of nanostructures based on wrinkled graphene.

Recently, carbon nanomaterials have attracted significant attention due to their remarkable physical and chemical properties. The preparation methods and applications of the carbon nanomaterials have developed rapidly. In this study, the flame synthesis of amorphous carbon film grown on copper foil in an ethanol inverse diffusion flame was presented. The effects of ethanol flow rate, the copper foil location in flame and growth time were investigated in detail. The growth status of the synthetic amorphous carbon film was analyzed by an optical microscope and HRTEM (high resolution transmission electron microscope). Raman spectroscopy and XRD (X-ray diffraction) were used to characterize the structure of the carbon film. The roughness of the carbon film was determined by AFM (atomic force microscopy). As the ethanol flow rate increased and the copper foil moved upwards in the flame, the area of the synthetic amorphous carbon film increased. The roughness of carbon films with the growth time of 30 s and 2 min were smaller. In addition, the synthetic amorphous carbon film exhibited a certain degree of flexibility and visual transparency. Through the study, a reference could be provided to find the optimum condition for the flame synthesis of satisfactory amorphous carbon film. For these experiments, when the ethanol flow rate reached 2 mL/min, the copper foil was located on the top of the flame and the growth time was 2 min, an amorphous carbon film with higher quality could be obtained.

Graphene nanomesh (GNM), an emerging graphene nanostructure with a tunable bandgap, has gained tremendous interests owing to its great potentials in the fields of high-performance field-effect transistors, electrochemical sensors, new generation of spintronics and energy converters. In previous works, GNM has been successfully obtained on copper foil surface by employing hydrogen as an etching agent. A more facile, and low-cost strategy for the preparation of GNM is required. Here, we demonstrated a direct and feasible means for synthesizing large-area GNM with symmetrical fractal patterns via a hydrogen-free chemical vapor deposition method. The influences of the growth time and the gas source flow on the morphology of GNM patterns were systematically investigated. Then, we exhibited the key reaction details and proposed a growth mechanism of the GNM synthesis during the hydrogen-free chemical vapor deposition process. This work provides a valuable guidance for quality control in GNM mass production.

Bilayer graphene is a contender of interest for functional electronic applications because of its variable band gap due to interlayer interactions. Graphene growth on Cu is self-limiting, thus despite the fact that chemical vapor deposition (CVD) has made substantial strides in the production of monolayer and single-crystal graphene on Cu substrates, the direct synthesizing of high-quality, large-area bilayer graphene remains an enormous challenge. In order to tackle this issue, we present a simple technique using typical CVD graphene growth followed by a repetitive wrinkling-etching-regrowth procedure. The key element of our approach is the rapid cooling process that causes high-density wrinkles to form in the monolayer area rather than the bilayer area. Next, wrinkled sites are selectively etched with hydrogen, exposing a significant portion of the active Cu surface, and leaving the remaining bilayer areas, which enhance the nucleation and growth of the second graphene layer. A fully covered graphene with 78 ± 2.8% bilayer coverage and a bilayer transmittance of 95.6% at room temperature can be achieved by modifying the process settings. Bilayer graphene samples are examined using optical microscopy (OM), scanning electron microscopy (SEM), Raman spectroscopy, and an atomic force microscope (AFM) during this process. The outcomes of our research are beneficial in clarifying the growth processes and future commercial applications of bilayer graphene.