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thermodynamic equilibrium potential, as shown in Figure 1. The HER process involves electro chemical H + adsorption and electrochemical/chemical desorption of H 2 , which is a two-electron transport process to generate a single H 2 molecule. By contrast, OER undergoes a four-electron transport coupled with the breaking of the OH bond, and the formation of the OO bond; therefore, for a kinetically hindered process, a high potential is needed to overcome the kinetic energy barriers. [12] To date, the OER remains a bottleneck in water splitting. Therefore, enormous efforts have been devoted to design and discover novel OER catalysts to satisfy the economic production of hydrogen from water splitting.Thus far, the benchmarks of OER catalysts in acidic solution are RuO 2 and IrO 2 , which are located on top of the volcanoplot, and express a relatively low overpotential (η), high current density, small Tafel slope, and high durability. [13,14] However, the wide utilization of RuO 2 or IrO 2 is hindered by high cost and insufficient reserves in the earth. Moreover, the aforementioned noble metal oxides are not the best OER electrocatalysts under alkaline conditions anymore. Their OER performances have been exceeded by several first-row transition metal based compounds (FTMCs). [15][16][17][18][19][20][21] Therefore, considerable attention has been focused on cost-effective alternatives that feature high electrocatalytic activity and life span. However, a relatively high overpotential (>300 mV) is still required by these nonprecious catalysts to reach a current density of 10 mA cm −2 , a widely used figure of merit that is equivalent to 12% solar-to-hydrogen efficiency. Thus, improving OER performance based on FTMCs is of great significance.Previous discoveries demonstrated that elemental doping is effective to boost the performance of FTMCs, given that the electronic structure of the catalysts can be tuned by dopants. [12,15] A well-known example is iron-doped nickel compounds, with trace amounts of iron-doped nickel hydroxides possibly enhancing the catalytic activity of OER significantly. [21][22][23] Thus, considerable efforts have been focused on optimizing elemental doping species and concentration and identifying the active sites of the catalysts. In addition to elemental doping, several novel and advantageous strategies have been developed Owing to its abundance, high gravimetric energy density, and environmental friendliness, hydrogen is a promising renewable energy to replace fossil fuels. One of the most prominent routes toward hydrogen acquisition is water splitting, which is currently bottlenecked by the sluggish kinetics of oxygen evolution reaction (OER). Numerous of electrocatalysts have been developed in the past decades to accelerate the OER process. Up to now, the first-row transition metal based compounds are in pole position under alkaline conditions, which have become subjects of extensive studies. Recently, significant advances in providing compelling catalytic performance as well as exploring t...

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a b s t r a c tA time-projection chamber (TPC) called the SAMURAI Pion-Reconstruction and Ion-Tracker (SπRIT) has recently been constructed at Michigan State University as part of an international effort to constrain the symmetry-energy term in the nuclear Equation of State (EoS). The SπRIT TPC will be used in conjunction with the SAMURAI spectrometer at the Radioactive Isotope Beam Factory (RIBF) at RIKEN to measure yield ratios for pions and other light isospin multiplets produced in central collisions of neutron-rich heavy ions, such as 132 Sn þ 124 Sn. The SπRIT TPC can function both as a TPC detector and as an active target. It has a vertical drift length of 50 cm, parallel to the magnetic field. Gas multiplication is achieved through the use of a multi-wire anode plane. Image charges, produced in the 12096 pads, are read out with the recently developed Generic Electronics for TPCs.

Abstract

We probe the momentum dependence of the isovector mean-field potential by comparing the energy spectra of neutrons and protons emitted in 112 Sn+ 112 Sn and 124 Sn+ 124 Sn collisions at incident energies of E/A=50 and 120 MeV. We achieve experimental precision that discriminates between different momentum dependencies for the symmetry mean-field potential. Comparisons of the experimental results to Improved Quantum Molecular Dynamics model calculations with Skyrme Interactions indicate small differences between the neutron and proton effective masses.

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Collisions involving 112 Sn and 124 Sn nuclei have been simulated with the Improved Quantum Molecular Dynamics transport model. The results of the calculations reproduce isospin diffusion data from two different observables and the ratios of neutron and proton spectra. By comparing these data to calculations performed over a range of symmetry energies at saturation density and different representations of the density dependence of the symmetry energy, constraints on the density dependence of the symmetry energy at sub-normal density are obtained. Results from present work are compared to constraints put forward in other recent analyses.