Hydrogen ions are ideal charge carriers for rechargeable batteries due to their small ionic radius and wide availability. However, little attention has been paid to hydrogen-ion storage devices because they generally deliver relatively low Coulombic efficiency as a result of the hydrogen evolution reaction that occurs in an aqueous electrolyte. Herein, we successfully demonstrate that hydrogen ions can be electrochemically stored in an inorganic molybdenum trioxide (MoO ) electrode with high Coulombic efficiency and stability. The as-obtained electrode exhibits ultrafast hydrogen-ion storage properties with a specific capacity of 88 mA hg at an ultrahigh rate of 100 C. The redox reaction mechanism of the MoO electrode in the hydrogen-ion cell was investigated in detail. The results reveal a conversion reaction of the MoO electrode into H MoO during the first hydrogen-ion insertion process and reversible intercalation/deintercalation of hydrogen ions between H MoO and H MoO during the following cycles. This study reveals new opportunities for the development of high-power energy storage devices with lightweight elements.
The aprotic lithium–oxygen (Li–O2) battery has triggered tremendous efforts for advanced energy storage due to the high energy density. However, realizing toroid-like Li2O2 deposition in low-donor-number (DN) solvents is still the intractable obstruction. Herein, a heterostructured NiS2/ZnIn2S4 is elaborately developed and investigated as a promising catalyst to regulate the Li2O2 deposition in low-DN solvents. The as-developed NiS2/ZnIn2S4 promotes interfacial electron transfer, regulates the adsorption energy of the reaction intermediates, and accelerates O–O bond cleavage, which are convincingly evidenced experimentally and theoretically. As a result, the toroid-like Li2O2 product is achieved in a Li–O2 battery with low-DN solvents via the solvation-mediated pathway, which demonstrates superb cyclability over 490 cycles and a high output capacity of 3682 mA h g–1. The interface engineering of heterostructure catalysts offers more possibilities for the realization of toroid-like Li2O2 in low-DN solvents, holding great promise in achieving practical applications of Li–O2 batteries as well as enlightening the material design in catalytic systems.
Cu-based electrocatalysts have seldom been studied for water oxidation because of their inferior activity and poor stability regardless of their low cost and environmentally benign nature. Therefore, exploring an efficient way to improve the activity of Cu-based electrocatalysts is very important for their practical application. Modifying electronic structure of the electrocatalytically active center of electrocatalysts by metal doping to favor the electron transfer between catalyst active sites and electrode is an important approach to optimize hydrogen and oxygen species adsorption energy, thus leading to the enhanced intrinsic electrocatalytic activity. Herein, Co-doped CuS nanodisks were synthesized and investigated as highly efficient electrocatalyst for oxygen evolution reaction (OER) due to the optimized electronic structure of the active center. Density-functional theory (DFT) calculations reveal that Co-engineered CuS could accelerate electron transfer between Co and Cu sites, thus decrease the energy barriers of intermediates and products during OER, which are crucial for enhanced catalytic properties. As expected, Co-engineered CuS nanodisks exhibit a low overpotential of 270 mV to achieve current density of 10 mA cm as well as decreased Tafel slope and enhanced turnover frequencies as compared to bare CuS. This discovery not only provides low-cost and efficient Cu-based electrocatalyst by Co doping, but also exhibits an in-depth insight into the mechanism of the enhanced OER properties.
Recent studies show that the Pt electrode can be slowly dissolved into the acidic media and regenerate on the working electrode along with the long-time hydrogen evolution reaction (HER) test. However, to date, the relationship between the Pt deposition and the intrinsic properties of the working electrode remains elusive. Herein, for the first time, the edge selectivity of in situ electrochemical Pt deposition on layered 2H-WS nanosheets, whose edge surface with rich dangling bonds is chemically active to regulate their properties, especially the interfacial reaction occurring between the electrode surface and the adjacent thin layer of the solution, is theoretically elucidated and experimentally verified by controlling the cathode polarization test using Pt wire as the counter electrode in H SO solution. It is revealed that the layered WS nanosheets with rich exposed edges show much stronger interaction with Pt atoms because the terminated S or S ligands on the edge exhibit much lower binding energy for Pt atoms compared with the apical S ligands on the terrace surface. The in situ electrochemical Pt-deposited WS nanosheets with rich exposed edges can act as a highly active hybrid electrocatalyst to accelerate HER kinetics and exhibit commercial Pt-like HER performance, especially in the alkaline media.
A novel method to recover rare earth elements (REEs) from NdFeB magnets was developed. This method involves three basic steps, i.e., the vacuum induction melting (VIM) process, the hydrolysis process and the magnetic separation process (HMS). In the VIM process, the NdFeB magnets were melted in a graphite crucible under vacuum (<1 Pa), in which way the rare earth carbides formed by the reaction of REEs and carbon, and the carbon saturated NdFeBCsat alloy was obtained. On the basis of the hydrolysis of rare earth carbides, the REEs were separated from the NdFeBCsat alloy by the reaction of the rare earth carbides phase with water. Thus, the rare earth hydroxides and iron-based metal residues were produced. Magnetic separation was further used to remove the iron residues from the rare earth hydroxides. Through this method, the optimal recovery ratio reached 93%, and the purity of the rare earth hydroxides was as high as 99.7%. Along with the VIM-HMS process, the investigation of NdFeBCsat alloy, the morphology of the rare earth hydroxides and the conversion of rare earth hydroxides to rare earth oxides are also presented in this paper. In this research, the X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductive-coupled plasma spectroscopy (ICP), mass spectrum analyses, CS analyses, magnetic properties analyses and nitrogen physisorption analyses were applied.
Developing photosensitizers with high extinction coefficients, proper electronic structures, and steric properties is warranted for the dye-sensitized solar cells (DSCs) employing one-electron outer-sphere redox shuttles. DSCs incorporating Co(II/III)tris(1,10-phenanthroline)based redox electrolyte and three synthesized organic dyes as photosensitizers (M14, M18, and M19) are described. The hexapropyltruxene group on the dyes retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the [Co(III)-(phenanthroline) 3 ] 3+ ions, which enables attainment of high photovoltages approaching 0.9 V. The measurement of photocurrent transients shows that the mass transport limitation of the cobalt redox shuttle has been largely removed by using thin TiO 2 films. DSCs sensitized with M14 in combination with the cobalt redox shuttle yield a DSC with an overall power conversion efficiency (PCE) of 7.2% under 100 mW cm −2 AM1.5 G illumination. The influences of the dye structure on the performance of DSCs were also investigated.
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