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Li-O2 battery technology offers large theoretical energy density, considered a promising alternative energy storage technology for a variety of applications. One of the main advances made in recent years is the use of soluble catalysts, known as redox mediators (RM), decreasing the charge overpotential and improving cyclability. Despite its potential, much is still unknown regarding its dynamic, especially over higher loading electrodes, where mass transport may be an issue and the interplay with common impurities in the electrolyte, like residual water. Here we perform for the first time an operando XRD characterization of a DMSO-based LiBr mediated Li-O2 battery with a high loading electrode based on CNTs aiming to reveal these dynamics and track chemical changes in the electrode. Our results show that, depending on the electrode architecture, the system's issue can move from catalytic to a mass transfer. We also assess the effect of residual water in the system to better understand the reaction routes. As a result, we observed that with DMSO, the system is even more sensitive to water contamination compared to glyme-based studies reported in the literature. Despite the activity of LiBr on the Li-peroxide oxidation and its contribution to cyclability, with the system and electrode configuration used in this study, we verified that a mass transfer limitation caused a cell "sudden death" caused by clogging after cycling.

The current study intends to characterize the microstructure resulting from the autogenous welding of zircaloy-4 and its influence on the mechanical behavior. For comparison purposes, laser beam welding (LBW) and electric resistance welding (ERW) were used for joint tubes to sleeves suitable for fuel elements of the Brazilian power reactor Angra 1. The tubes measured 14.15 mm external diameter with a wall thickness of 1.76 mm and the sleeves measured 15.61 internal diameter with a wall thickness of 0.64 mm. Under conventional ERW, the process parameters were chosen to produce an approximately 2 mm wide weld bead appropriate for the thermo-mechanical loading of the component. However, laser methods could be an alternative for automation and reproductiity. The microstructure in the fusion zone (FZ) for the welding processes was characterized by α martensite for LBW and α Widmanstätten for ERW. It was verified tin segregation in specific regions of the ERW coupons, however, without affecting the tensile strength or the hardness of the coupons. The maximum load for ERW coupons were about 8 kN, higher than LBW case (3 kN), although both above the standard requirements. The relative low value of LBW tensile strength was due to the gap between the tube and the sleeve, as conceived for ERW, and not optimized for the laser process. Loss of coolant accident (LOCA) shown a white ZrO2 coating on the LBW surface as a result of massive oxidation of the resolidified material. Keywords: Zirconium alloys, Electric resistance welding, Laser welding

Cashew apple bagasse (CAB) has been studied as feedstock for the biohydrogen production using Clostridium roseum and the dark fermentation process. Pretreatment with alkaline hydrogen peroxide (CAB-AHP) on raw material and the acid and enzymatic hydrolysis have been taken into account to evaluate the H2 yields. Results show that the acid hydrolysate obtained from CAB produced higher H2 molar yield (HMY) (15 mmolH2/Lhydrolysate) than the acid hydrolysate from CAB-AHP (4.99 mmolH2/Lhydrolysate), These HMY were noticeably higher than values obtained from the enzymatic hydrolysate of CAB-AHP (1.05 mmolH2/Lhydrolysa) and the enzymatic hydrolysate of CAB (0.59 mmolH2/Lhydrolysa). The maximum biohydrogen productivity (12.57 mLH2/L.h) was achieved using the acid hydrolysate from CAB, with a H2 content of about 72% vol, that could be satisfactory in view of an energetic applications of the biogas. Results suggest that CAB could be considered for the hydrogen production process, providing an appropriate destination for this lignocellulosic biomass, and consequently, reducing the environmental impact it can exert.

AbstractNickel nanoparticles supported by commercial carbon paper (CP) are prepared by pulsed laser deposition with deposition time of 3, 6, and 12 min as a catalyst for urea electro-oxidation. The surface conditions and the morphologies of the prepared electrodes have been characterized by Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Urea electro-oxidation reaction in KOH solution on the Ni/CP electrodes is investigated by cyclic voltammetry and chronoamperometry. The results show that the electrode with less Ni nanoparticle agglomeration shows higher peak current density, which was achieved in the 3 min deposition samples when normalized by electroactive surface areas. However, the highest current normalized by the area of the carbon paper was achieved in the 6 min deposition sample due to the larger quantity of Ni nanoparticles. All the samples show good stability. Our results suggest that the low density, low cost, and environmental friendly CP can be used as support for Ni nanoparticle as a catalyst for urea electro-oxidation. It thus has great potential for many applications involving urea oxidation, such as wastewater treatments.

The purpose of this investigation was to compare catalysts produced by the Bönnemann - colloidal method (PtRu (B1) and PtRu (B2)), and those produced by the spontaneous deposition method (PtRu (SD)). The catalysts produced by both methods had good electrochemical behavior for methanol oxidation for proton exchange membrane fuel cell applications. The structure of the catalyst was examined by transmission electron microscopy (TEM). Energy dispersive spectroscopic analysis (EDS) was used to determine the semi-quantitative composition of the catalysts, and the electrochemical behavior was determined by cyclic voltammetry (CV). The diffractograms of the binary catalysts revealed platinum and ruthenium as the only crystalline phases, as per ICDD data base. The PtRu (B1) catalyst, treated in a reducing atmosphere, has the same structure as PtRu (B2), treated in an oxidising/reducing atmosphere, except that the crystallite size was around 1.7 nm for PtRu (B1) instead of 9.9 nm for PtRu (B2). The catalysts PtRu (B2) and PtRu (SD) showed similar cyclic voltammetric behavior, which was better than that of PtRu (B1). Both methods are suitable for the production of electrocatalysts for fuel cell applications. The colloidal method is more expensive than the deposition method, but the former permits the production of ternary and quaternary catalyst systems with enhanced CO tolerance.

We present an efficient synthesis technique to derive highly stable anode for lithium-ion batteries.

This work aimed to study the potential use of pyrolyzed orange peels as solid biofuels and biosorption of heavy metals. The dry biomass and the biofuel showed moderate levels of carbon (44-62%), high levels of oxygen (30-47%), lower levels of hydrogen (3-6%), nitrogen (1-2.6%), sulfur (0.4-0.8%) and ash with a maximum of 7.8%. The activation energy was calculated using Kissinger method, involving a 3 step process: volatilization of water, biomass degradation and volatilization of the degradation products. The calorific value obtained was 19.3MJ/kg. The studies of metal biosorption based on the Langmuir model obtained the best possible data fits. The results obtained in this work indicated that the potential use of waste orange peel as a biosorbent and as a solid biofuel are feasible, this product could be used in industrial processes, favoring the world economy.