Carbide-derived Carbon (CDC) has been demonstrated to be an excellent electrode material for electrochemical devices including supercapacitors due to its chemical and electrochemical stability, large specific surface area and controllable pore size and morphology. Currently, CDC is prepared from metal carbides by chlorination in a chlorine gas atmosphere at temperatures of 350 • C or higher. In this paper, conversion using electrochemical methods is reported, which can be achieved by oxidizing vanadium carbides (VC or V 2 C) in aqueous solutions at room temperature and a mild electrode potential to prepare CDC thin film as electrode materials for "on-chip" supercapacitiors. It was found that VC and V 2 C can both be oxidized at a potential of about 0.4 V vs. Ag/AgCl or higher in neutral, acidic, or basic solutions. After the oxidation, vanadium is readily detected in the electrolyte solutions by ICP-MS (Inductively Coupled Plasma -Mass Spectrometry). The so-produced CDC thin film electrode (ca. 2.0 -2.6 μm thick) has a porous morphology and bears specific double layer capacitance values as high as 0.026 F.cm −2 (or 130 F.cm −3 ) with some dependence on the oxidation potential, time, and electrolyte solutions. Carbide-Derived carbon (CDC) is a new type of porous carbon material demonstrating high purity, a narrow distribution of pore sizes, and significant specific surface area.1,2 Due to these unique properties, CDC was found to be very useful for gas storage, flow sensors, and as an electrode material for electrochemical energy storage devices such as supercapacitors.3-7 Currently, the most reliable method to synthesize CDC is to remove the metal or metalloid elements selectively from binary or ternary carbide precursors. 1,8,9 This has been achieved by chlorine gas treatment (chlorination) at a temperature of 350• C or higher. At an elevated temperature, metal / metalloid elements can be reacted to be volatile metal chlorides and purged using an argon gas stream. Thus, the left-over carbon is metal free and sp 2 or sp 3 hybridized. To date, CDC has been successfully synthesized from binary carbides such as TiC, Cr 3 C 2 , Fe 3 C, Mo 2 C, Nb 2 C, SrC 2 , Ta 2 C, VC, V 2 C WC, W 2 C, ZrC, as well as ternary carbides (also called MAX phase carbides) such as Ti 2 AlC, Ti 3 AlC 2 . Most of this work has been performed in bulk solids/powders. Depending on the crystalline/ elemental structure of the precursor and the reaction temperature, the pore size of CDC can be controlled in the range over 2-50 nm.1 The theoretical bulk porosity is between 50-90% in volume. Thus far, the Cl 2 reaction method of etching has been primarily used but one downside is that the Cl 2 gas is toxic, corrosive and the process itself is relatively expensive. On the other hand, an alternative oxidation method is to prepare CDC under more environmentally favorable conditions that have been rarely explored. For example, Y. Gogotsi and coauthors reported the electrochemical etching of MAX-phase carbides to produce CDC at room temperature using ...

Purpose Silicate rock powders have been appointed as possible nutrient alternative sources which might enhance the agricultural sector sustainability. However, the application of those materials directly in soil presents as main limitations the low content and solubility of the mineral nutrient sources. In this perspective, the aim of the present study was to evaluate, in a bioweathering perspective, the conjunct application potential of phonolite with organic composts over the nutrients release in soil, as well as the production and nutrition of brachiaria grass (Urochloa decumbens). In addition, it was sought to assess the composting process effectiveness in improving the nutrient release from this rock. Method An experiment was conducted with five treatments (control; enriched compost with powder rock at 10%; mixed compost with powder rock at 10%; solely powder rock; solely compost) and four repetitions. Results The alternative sources positively influenced the productivity, as well as the K and Si contents at the aerial part of the brachiaria grass and the nutrient release in soil. However, the conjunct applications of powder phonolite with organic composts were the source which the best promoted the total nutrient biorelease to soil. Conclusion Nevertheless, there was no evidence that the composting process promotes the phonolite bioweathering. On the other hand, the conjunct application of powder phonolite with organic composts, either as an initial component to the composting pile or additive to the stabilized composts, is a strategy which enhances the nutrient biorelease of the mineral source.

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Recently, graphene nanoribbons (GNR) have gained prominence for applications in high performance electrodes. However, this material might present some complications, such as restacking formation, lower electron mobility due to oxygen-containing functionalities and non-reversible structural damages related to oxidation processes, decreasing GNR response. Several papers sought to minimize this limitation, but the most part use high cost materials, rendering ineffective or hard the application of this device. Less expensive alternatives have to show up, enabling a viable cost/performance ratio. In this sense, the aim of this study was to evaluate the performance of electrodes built from the incorporation of graphene oxide nanoribbons (O-GNR) in carbon paste electrodes (CPE), at different mass percentages (w/w), applied as high performance electrodes. O-GNR synthesis was made through an adaptation of the longitudinal unzipping of multiwalled carbon nanotubes method. Experimental results demonstrated that the simple dispersion of O-GNR in carbon paste electrodes is enough to enhance the response of this material, reaching a double layer capacitance as high as 350 mF cm −2 in 1.0 mol L −1 KCl solution. Scan rate up to 300 mV s −1 showed to disturb the double layer capacitance for all electrodes evaluated.