Cobalt phosphide nanorods as an efficient electrocatalyst for the hydrogen evolution reaction

Cobalt phosphide (Co2P) nanorods are found to exhibit efficient catalytic activity for the hydrogen evolution reaction (HER), with the overpotential required for the current density of 20mA/cm2 as small as 167mV in acidic solution and 171mV in basic solution. In addition, the Co2P nanorods can work stably in both acidic and basic solution during hydrogen production. This performance can be favorably compared to typical high efficient non-precious catalysts, and suggests the promising application potential of Co2P nanorods in the field of hydrogen production. The HER process follows a Volmer-Heyrovsky mechanism, and the rates of the discharge step and desorption step appear to be comparable during the HER process. The similarity of charged natures of Co and P in the Co2P nanorods to those of the hydride-acceptor and proton-acceptor in highly efficient Ni2P catalysts, [NiFe] hydrogenase, and its analogues implies that the HER catalytic activity of the Co2P nanorods might be correlated with the charged natures of Co and P

9R phase enabled superior radiation stability of nanotwinned Cu alloys via in situ radiation at elevated temperature

Nanotwinned metals exhibit outstanding radiation tolerance as twin boundaries effectively engage, transport and eliminate radiation-induced defects. However, radiation-induced detwinning may reduce the radiation tolerance associated with twin boundaries, especially at elevated temperatures. Here we show, via in-situ Kr ion irradiation inside a transmission electron microscope, that 3 at. % Fe in epitaxial nanotwinned Cu (Cu97Fe3) significantly improves the thermal and radiation stability of nanotwins during radiation up to 5 displacements-per-atom at 200 °C. Such enhanced stability of nanotwins is attributed to a diffuse 9R phase resulted from the dissociation of incoherent twin boundaries in nanotwinned Cu97Fe3. The mechanisms for the enhanced stability of twin boundaries in irradiated nanotwinned alloys are discussed. The stabilization of nano-twins opens up opportunity for the application of nanotwinned alloys for aggressive radiation environments. Includes supplemental Appendix. Video files are attached below

Strong Exponential Attractors for Weakly Damped Semilinear Wave Equations

In this paper, we investigate the longtime dynamics for the damped wave equation in a bounded smooth domain of ℝ3. The exponential attractor is investigated in a strong energy space for the case of subquintic nonlinearity, which is based on the recent extension of the Strichartz estimate for the case of a bounded domain. The results obtained complete some previous works

Existence of multiple equilibrium points in global attractor for damped wave equation

Abstract This paper is a continuation of Meng and Zhong in (Discrete Contin. Dyn. Syst., Ser. B 19:217–230, 2014). We go on studying the property of the global attractor for some damped wave equation with critical exponent. The difference between this paper and Meng and Zhong in (Discrete Contin. Dyn. Syst., Ser. B 19:217–230, 2014) is that the origin is not a local minimum point but rather a saddle point of the Lyapunov function F for the symmetric dynamical systems. Using the abstract result established in Zhang et al. in (Nonlinear Anal., Real World Appl. 36:44–55, 2017), we prove the existence of multiple equilibrium points in the global attractor for some wave equations under some suitable assumptions in the case that the origin is an unstable equilibrium point

Design, Analysis, and Experiment for Rescue Robot with Wheel-Legged Structure

A wheel-legged rescue robot design with strong environmental adaptability is proposed. The design presented is aimed at helping rescue workers complete their missions, such as environmental and personnel search, quickly and accurately. So it has broad application prospects. In order to achieve the advantages of simple structure, easy control, small occupation space, and wide motion range, a wheel-legged rescue robot is designed in this paper, and the robot can realize three kinds of motion states, which include wheel state, rotation center lifting process, and leg state. Then the motion states are analyzed in detail, which provides a reference for motion control. Considering the wheel state and leg state share the same structure to contact with the ground, the effect of the stiffness of wheel-legged structure to the motion performance is analyzed. Then the experiment is carried out to prove the feasibility of the structure design. This study offers a design and quantitative analysis for wheel-legged rescue robot. Furthermore, a basis for future control research and engineering applications is established

Dual Beam In Situ Radiation Studies of Nanocrystalline Cu

Nanocrystalline metals have shown enhanced radiation tolerance as grain boundaries serve as effective defect sinks for removing radiation-induced defects. However, the thermal and radiation stability of nanograins are of concerns since radiation may induce grain boundary migration and grain coarsening in nanocrystalline metals when the grain size falls in the range of several to tens of nanometers. In addition, prior in situ radiation studies on nanocrystalline metals have focused primarily on single heavy ion beam radiations, with little consideration of the helium effect on damage evolution. In this work, we utilized in situ single-beam (1 MeV Kr++) and dual-beam (1 MeV Kr++ and 12 keV He+) irradiations to investigate the influence of helium on the radiation response and grain coarsening in nanocrystalline Cu at 300 °C. The grain size, orientation, and individual grain boundary character were quantitatively examined before and after irradiations. Statistic results suggest that helium bubbles at grain boundaries and grain interiors may retard the grain coarsening. These findings provide new perspective on the radiation response of nanocrystalline metals

9R phase enabled superior radiation stability of nanotwinned Cu alloys via in situ radiation at elevated temperature

Nanotwinned metals exhibit outstanding radiation tolerance as twin boundaries effectively engage, transport and eliminate radiation-induced defects. However, radiation-induced detwinning may reduce the radiation tolerance associated with twin boundaries, especially at elevated temperatures. Here we show, via in-situ Kr ion irradiation inside a transmission electron microscope, that 3 at. % Fe in epitaxial nanotwinned Cu (Cu97Fe3) significantly improves the thermal and radiation stability of nanotwins during radiation up to 5 displacements-per-atom at 200 °C. Such enhanced stability of nanotwins is attributed to a diffuse 9R phase resulted from the dissociation of incoherent twin boundaries in nanotwinned Cu97Fe3. The mechanisms for the enhanced stability of twin boundaries in irradiated nanotwinned alloys are discussed. The stabilization of nano-twins opens up opportunity for the application of nanotwinned alloys for aggressive radiation environments. Includes supplemental Appendix. Video files are attached below

Phase separation synthesis of trinickel monophosphide porous hollow nanospheres for efficient hydrogen evolution

A facile and scalable approach to synthesize trinickel monophosphide (Ni₃P) porous hollow nanospheres (PHNs) has been developed, the resultant Ni₃P PHNs exhibiting excellent catalytic activity in the hydrogen evolution reaction (HER). The formation of the Ni₃P PHNs correlates with phase separation during the thermal annealing of amorphous nickel–phosphorus nanospheres that affords crystalline Ni–Ni₃P nanoparticles, and the subsequent selective removal of nickel. The overpotential required for the current density of 20 mA cm−2 is as small as 99 mV in acidic solution. The performance compares favorably with that of other metal phosphides, and is superior to that of transition metal dichalcogenides, carbides, borides, and nitrides. The faradaic efficiency of the Ni₃P PHNs is 96%, and the Ni₃P PHNs are stable during the long-term electrolysis of water. Density functional theory calculations suggest that a Ni–Ni bridge site and the sites on the top of the P atoms are the active sites during the HER. The scalable production, low cost, excellent catalytic activity, and long-term stability suggest promising application potential for Ni₃P PHNs.This research was financially supported by the National Natural Science Foundation of China (61006049, 51432006, 51172100), the Ministry of Science and Technology of China (2011DFG52970), the Ministry of Education of China (IRT14R23), 111 Project (B13025), Jiangsu Province (2011-XCL019 and 2013-479), and the Natural Science Foundation of Jiangsu (BK20131252)

Ultrafast synthesis of molybdenum carbide nanoparticles for efficient hydrogen generation

A facile and ultrafast synthesis of molybdenum carbide coated with few-layer carbon (MoC/C) has been developed, and the effect of reducing the thickness of the carbon coating on its catalytic activity in the hydrogen evolution reaction (HER) has been demonstrated. MoC/C produces a current density of 20 mA cm−2 at an overpotential of 144 mV and a Tafel slope of 63.6 mV dec−1 in 0.5 M H2SO4, and works stably under long-term electrolysis. MoC/C is one of the most active carbide electrocatalysts reported thus far, although MoC is not even the most active phase of molybdenum carbide and MoC/C has a small surface area. Complementary density functional theory calculations have afforded insight into this novel catalyst design, showing that increasing the thickness of the carbon layer leads to the composite system losing the characteristics of MoC and behaving more like a carbon surface, and thereby resulting in a reduction in HER activity.This research was nancially supported by the National Natural Science Foundation of China (51772214, 51432006), the Ministry of Science and Technology of China (2011DFG52970), the Ministry of Education of China (IRT14R23), the 111 Project (B13025), Jiangsu Province (2011-XCL-019 and 2013-479). M. G. H. and C. Z. thank the Australian Research Council for support