A microelectromechanical-systems-based calorimeter designed for use on a synchrotron nano-focused X-ray beamline is described. This instrument allows quantitative DC and AC calorimetric measurements over a broad range of heating/cooling rates (≤100000 K s(-1)) and temperature modulation frequencies (≤1 kHz). The calorimeter was used for high-resolution thermal imaging of nanogram-sized samples subjected to X-ray-induced heating. For a 46 ng indium particle, the measured temperature rise reaches ∼0.2 K, and is directly correlated to the X-ray absorption. Thermal imaging can be useful for studies of heterogeneous materials exhibiting physical and/or chemical transformations. Moreover, the technique can be extended to three-dimensional thermal nanotomography.

In recent years, the key principles of the electric power industry have radically changed and the number of studies on the development of devices for electrical energy storage in a different form such as mechanical or chemical energy has rapidly increased. This review gives a brief description of these devices. The attention is focused on redox flow batteries (RFBs), a promising type of energy storage devices capable of efficiently operating in distributed power grids, in order to eliminate the imbalance between the time-varying electricity production by ‘unconventional sources’ and electricity consumption. At the design level, RFBs combine the principles of fuel cells and chemical energy sources with solid electroactive materials: transitions between electrical and chemical forms of energy in these devices occur upon oxidation and reduction of redox-active electrolytes, which are stored in separate tanks and pumped into the electrode compartments of the membrane electrode assembly (MEA) separated by a semi-permeable membrane. This approach ensures an important advantage of these devices over other types of chemical energy sources, that is, the possibility of independent scaling of the energy storage capacity and power characteristics of the system. This review provides a systematic description of the main types of RFBs and analysis of their fundamental benefits and drawbacks, which determine the prospects for practical applications of RFBs. The bibliography includes 149 references.

International audienceThe study is devoted to analyzing the electroreduction of bromate anion BrO (3) (-) on catalytically inactive (e.g., carbon) electrodes by numerical methods. This process is realized due to the combination of the reversible mediator pair Br-2/Br- and the process of comproportionation (reaction of bromate and bromide anions) in solution phase. These reactions increase the concentration of bromine and bromide near the electrode surface; hence, this process is autocatalytic (ECaEuro(3) mechanism). Within the framework of this study, a numerical algorithm which allows the system of diffusion-kinetic equations to be solved for this system is proposed for one-dimensional transport and the process under steady-state conditions. The results are compared with the conclusions of the approximate analytical theory published in Electrochim. Acta, 2015, vol. 173, p. 779, which allows inferring that both approaches are correct. The deviation between the latter is observed only in the cases of violation of approximations lying in the basis of the corresponding analytical relationships. Thus, the predictions of the analytical theory of practical interest can be considered as reliably confirmed by numerical calculations, particularly, the prediction on the nonmonotonous dependence of the maximum current on the diffusion layer thickness (or the RDE rotation rate) including the anomalous region of this dependence in which the current increases with the increase in the diffusion layer thickness

A concept of high energy density (ED) hydrogen–bromate flow battery was supported by experiments with flow cells with 0.1 to 50 cm2 apparent areas. H2/NaBrO3 flow cells with H2 gas diffusion anode, proton exchange membrane (PEM), and carbonaceous flow‐by or flow‐through cathodes were employed. Estimates show that the theoretical ED of the H2/bromate flow battery (HBFB) exceeds the ED of H2/O2 fuel cells (FC) in air‐deficient environments. At the cathode of the HBFB, aqueous, concentrated bromate (non‐toxic, and stable) is reduced to bromide by a six‐electron process. 100 % conversion of BrO3− to Br− can be achieved. Although acidification of the BrO3− electrolyte is a prerequisite, the acid concentration in the electrolyte feed can be optimized as a trade‐off between area specific power (P) of the HBFB and its complexity.