Ionics

In the development of renewable energy systems, finding low-cost and high-performance electrocatalysts for hydrogen evolution reaction and oxygen evolution reaction under the synergistic action of bimetals is a challenge. This paper firstly describes the growth of Zn-Ni-M/NF (M = O/P/Se/S) nanostructured samples on nickel foam through thermal decomposition, phosphating, selenization, and sulfidation. A current density of 50 mA cm−2 is driven at an overpotential of 160 mV for oxygen evolution reaction, and a current density of 10 mA cm−2 is driven at an overpotential of 117 mV for hydrogen evolution reaction. In a two-electrode system, only a cell voltage of 1.49 V is required to drive a current density of 10 mA cm−2, which is almost one of the best catalysts reported so far. In addition, the work also provides a wide range of possibilities for the development of the earth’s abundant resources and that of cheap and efficient catalyst materials.

Lithium–sulfur (Li-S) battery has been considered to be one of the next-generation high-energy-density rechargeable battery systems due to the high theoretical energy density, low cost, and environmental friendliness. However, the commercial application of Li-S battery still faces problems such as sluggish redox kinetics and infamous shuttle effect of sulfur cathode, which result in low sulfur utilization, poor cycle life, and unsatisfied rate performance. Herein, we proposed a CoSe2-NC nanocluster anchored honeycomb-like carbon framework (CoSe2-NC@HCF) as sulfur host aiming to accelerate sulfur conversion and inhibit polysulfide shuttle in Li-S electrochemistry via space-confined growth and in situ selenization. The obtained CoSe2-NC@HCF provides strong chemical adsorption capability and massive polar cobalt active sites as well as abundant and continuous hierarchical pores supplying adequate sulfur storage space and physical confinement. The S/CoSe2-NC@HCF cathode with sulfur content of 83.24 wt% delivers high sulfur utilization with initial discharge capacity of 1212.9 mAhg−1 at 0.1 C, excellent rate performance with 1094.7 mAh·g–1 at 1C rate, and good cyclability with low-capacity decay rate of 0.12% up to 600 cycles.

Ethanol and methane are compared as candidate fuels for generation of electrical power in Solid Oxide Fuel Cells (SOFCs). The thermodynamic analysis of both alternatives was undertaken considering that a SOFC operates with the equilibrium products of the steam reforming of each raw fuel. The comparison was made assuming SOFC operation under atmospheric total pressure in the temperature range of 800–1200K, and results were obtained in terms of the maximun theoretical electromotive force (emf) and the thermodynamic efficiency of total energy conversion. It was found that although methane fueled SOFCs are able to provide slightly higher efficiencies, ethanol is a competitive alternative fuel with suitable characteristics.

Disordered and amorphous compounds sometimes show better properties as cathodes than crystalline compounds of the same material in lithium electrochemical devices. In the present work, we have considered molybdenum compounds such as MoO3 and MoS2 having different degrees of structural disorder which are being extensively investigated as intercalation hosts of lithium for applications in rechargeable batteries or electrochromic devices. In this connection, their potential-composition curves have been measured as thermodynamic characteristic which is very important from both fundamental and practical point of view. Considering both ionic and electronic contributions to the charge/discharge behavior, the electrochemical features are discussed from the point of view of energy diagrams.

A novel Sr-based perovskite electrolyte, SrCe0.5Zr0.35Y0.1Gd0.05O3-δ, was successfully synthesized and characterized in comparison with SrCe0.5Zr0.35Y0.1Sm0.05O3-δ for possible use in proton-conducting solid oxide fuel cells. Indexing and subsequent Rietveld refinement confirm that both materials crystallize in the orthorhombic symmetry with Pbnm space group. Scanning electron microscopy images show the highly dense structure with the relative densities of 96% and 97% for Gd and Sm-doped sample, respectively. Electrochemical impedance measurements in wet 5% hydrogen at 700 °C shows that the conductivity of SrCe0.5Zr0.35Y0.1Gd0.05O3-δ and SrCe0.5Zr0.35Y0.1Sm0.05O3-δ were 5.701 ×10−3 S cm−1 and 5.257 × 10−3 S cm−1, respectively. The ionic conductivities of both samples increase in the wet hydrogen compared with that of dry hydrogen atmosphere. This indicates the enhancement of protonic conduction mechanism from introducing water in electrochemical impedance measurement. The proton conduction takes place at a lower temperature than conventional solid oxide fuel cell (SOFC) which makes SrCe0.5Zr0.35Y0.1(Gd/Sm)0.05O3-δ good electrolytes for intermediate-temperature solid oxide fuel cell (IT-SOFC).

In this work, a comparative study is presented utilizing a K+ conducting gel polymer electrolyte (GPE) system comprising of a poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) polymer matrix combined with potassium permanganate (KMnO4) salt and two different plasticizers as a binary combination of ethylene carbonate (EC) + propylene carbonate (PC) and tetraethylene glycol dimethyl ether (TEGDME). The electrolyte with TEGDME solvent shows an ionic conductivity (σ) of 7.01 × 10−6 S cm−1 with hopping of ions as charge transport behavior. The fabricated electrolyte possesses > 98% contribution from the ions, and the electro-chemical stability range is up to 3.2 V. The dielectric analysis shows that the electrolyte with TEGDME solvent possesses a higher value of the dielectric constant, dielectric loss, tangent loss, and dc conductivity, along with a higher free ion number density (N) in comparison to the counter-electrolyte specimens with EC:PC solvent. The thermal studies confirm the gel phase of both electrolytes with negligible weight loss till 100 °C. Polymer-salt complex interactions are confirmed using Fourier transform infrared spectroscopy (FTIR), while X-ray diffraction (XRD) analysis is used to study the variations in crystallinity brought about by the polymer and both electrolyte samples.