Enhancement of Ampere-Level Current Density of Multicarbon Products by Doping and Stress-Regulated Cu Dual Sites

The field emission (FE) properties of nickel nanoparticles embedded in thin silica matrix irradiated with 100 MeV Au+7 ions at various fluences are studied here. A large increase in FE current density is observed in the irradiated films as compared to their as deposited counterpart. The dependence of FE properties on irradiation fluence is correlated with surface roughness, density of states of valence band and size distribution of nanoparticles as examined with atomic force microscope, X-ray photoelectron spectroscopy, and grazing incidence small angle x-ray scattering. A current density as high as 0.48 mA/cm2 at an applied field 15 V/μm has been found for the first time for planar field emitters in the film irradiated with fluence of 5.0 × 1013 ions/cm2. This significant enhancement in the current density is attributed to an optimized size distribution along with highest surface roughness of the same. This new member of field emission family meets most of the requirements of cold cathodes for vacuum micro/nanoelectronic devices.

Interlayer modification for high-performance and stable solid oxide electrolysis cell

Enhancement of critical current density in HgBa 2Ca 2Cu 3O 8+ δ superconductor doped by Sb

The present study discovers the significant enhancement of critical current density by the pinning of borohydride and crystal defects in the hydrogen-treated MgB2 bulks. Based on the concept of gas doping, the nanosized borohydride Mg(BH4)2 is formed by synthesizing H-doped MgB2 bulks in an H2 atmosphere at 300 °C and 350 °C, and the critical current density was enhanced over the entire field. The H-doped MgB2 bulks are then experienced dehydrogenation at 300 °C and 350 °C, respectively, and the decomposition of Mg(BH4)2 induced nanosized pits on the surface of the MgB2 grains, leading to a further enhancement of critical current density, 1.5 × 104 A cm−2 at 20 K and 2.5 T, which is three times larger than that of the un-doped MgB2 sample, 4.8 × 103 A cm−2. The hydrogenation and dehydrogenation hardly changed the superconducting transition temperature or the pinning mechanism of the MgB2 samples. The enhancement of the critical current density is possibly attributed to the pinning effects of the crystal defects, and the reduction of MgO.

Engineering the desired dual metal sites to realize C–C coupling of CO 2 is of great importance for the practical applications of CO 2 electroreduction reaction (CER). Herein, an efficient strategy for constructing heterogeneous Pt δ + –Cu δ + dual sites to strengthen the generation and coupling of *CO and *CHO (or *COH) during CER process is presented in this work. The radii‐larger Pt not only stabilizes the Cu δ + but also induces a tensile strain in Pt δ + –Cu δ + dual sites. The obtained Pt δ + –Cu δ + dual sites achieve a total Faradaic efficiency and current density of C 2 products with 70.9% and 586.9 mA·cm −2 at – 1.20 V (vs. RHE), which is higher than that of Cu δ + single site (55.4%, 286.9 mA·cm −2 ). The in situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) reveals that the Pt δ + –Cu δ + dual sites can promote the generation of C 1 intermediates (such as *CO, *COOH, *COH, and *CHO) and C–C coupling. Additional in situ surface‐enhanced Raman spectra demonstrate that Pt δ + –Cu δ + dual sites can induce the generation of the high‐frequency peak for *CO atop , thus accelerating the C–C coupling. This work provides a promising avenue for stabilizing and enhancing the performance of Cu δ + sites toward CER.

Using the high-resolution Faraday technique, domain patterns of flux penetration in heavy-ion-irradiated ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ thin films are obtained. To compare the influence of different projectiles, the samples were irradiated with 25-MeV oxygen ions, 230-MeV nickel ions, and 1-GeV lead ions with various fluences perpendicular to the sample surface and hence parallel to the c axis of the materials. The irradiation with $^{16}\mathrm{O}$ produces point-defect cascades mainly perpendicular to the path of the projectile whereas the irradiation using $^{58}\mathrm{Ni}$ ions creates spherical regions of amorphized material along the path. The $^{208}\mathrm{Pb}$ ions create columnar tracks along the c axis of the material. For a simultaneous observation of irradiated and unirradiated regions of a single epitaxial thin film, only one-half of each sample was exposed to the irradiation. To obtain data for the acting-volume pinning forces and the local critical current densities, a numerical calculation also regarding the curvature of the flux lines is carried out. Oxygen and nickel irradiation lead to an enhancement of the critical current density by a factor of 2. By lead irradiation, an enhancement of the critical current density up to a factor of 5 is obtained. This critical current density at the largest fluence used reaches the theoretical predictions for an enhancement of the critical current density by means of irradiation-induced columnar tracks. The effects of the irradiation-induced defects are compared to those of the pinning sites present in the background pinning. The density of the irradiation-induced columnar defects and their influence on the pinning are compared to the density and effect of screw dislocations. Our results clearly indicate that screw dislocations do not act as effective pinning centers because of their small density.

Bulk MgB2 sample with carbon nanotube (CNT)-coated Al addition was prepared by conventional solid-state reaction at 900 °C for 30 min. We investigated the effects of Al and C co-doping on the lattice parameter, the microstructure, and the critical current density of MgB2. The substitution of Al and C atoms for the sites of Mg and B in the MgB2 lattice resulted in dislocations in the MgB2 grains, which makes great contributions, along with the nanoscale oxide particles, to the enhancement of critical current density at high field (103 A cm−2, 7 T, 5 K) in the co-doped sample. These results contrasted significantly with the measured values of the pure MgB2 and Al- and C-doped samples. Co-doping introduced more electrons into MgB2 and decreased both the parameters c and a of MgB2 lattice, and the used coating technique delayed and shortened the oxidation process of Mg and Al, leading to the decrease in the size and the content of the oxide. These advantages should be responsible for the enhancement of the critical current density as well.

The present study discovers the significant enhancement of critical current density by borohydride pinning in H-doped MgB2 bulks. Second-phase borohydrides are formed by synthesizing MgB2 bulks ex situ in an H2 atmosphere and in situ with H-trapped boron based on the concept of gas doping. Second phase Mg(BH4)2 appears in the samples ex situ sintered in an H2 atmosphere, leading to an enhancement of critical current density at magnetic fields over 3 T. Moreover, the in situ synthesized samples from H-trapped boron also exhibit a significantly enhanced critical current density of 1.8 × 104 A cm−2 at 20 K and 3 T, due to Mg(BH4)2 pinning centers that are embedded in the MgB2 grains. In contrast, the critical current density is only 9.6 × 103 A cm−2 at 20 K and 3 T in an un-doped MgB2 sample.

For a single-substance catalyst, due to the different adsorption/desorption kinetics of metallic (cationic) and nonmetallic (anionic) sites, it typically catalyzes hydrogen evolution in a single-active-site manner, which greatly limits the activity of catalysts. Thus, herein, we simultaneously activate the anion (P) and cation (Ni) sites in nickel phosphide (Ni2P) and generate highly active P(Ni) dual sites through the substrate effect of NiS2-NiS heterogeneous structures. Theoretical calculation results combined with in situ Raman spectroscopy unveil that the NiS2-NiS substrate effectively regulates the charge distribution to concentrate around the P atom, therefore resulting in Ni and P synergistic dual active sites for water adsorption, water dissociation, and H* adsorption. Accordingly, the dual active site formed enables the Ni2P/NiS2-NiS electrocatalyst to only require an overpotential of 75 mV to achieve a current density of 10 mA cm-2 in alkaline media, very close to the Pt-group noble metal catalyst. This work highlights the critical regulatory role of substrates in activating the anion-cation dual active site in the single metal/intermetallic compound (such as metal phosphides, sulfides, nitrides, carbides, borides, and silicides) that promotes catalytic performance.

We describe the enhancement of electron injection by external light irradiation in organic light-emitting diodes (OLEDs) with a charge generation layer (CGL). Under He–Ne laser irradiation, photon-induced charge generation under electric field occurred in the CGL. Electrons and holes were generated in the CGL and the electrons were directly injected into adjacent electron transport layers. As a result, the enhancement of current density under light irradiation was observed. A thousand fold enhancement of current density was obtained for light irradiation under forward biased condition. Current density was determined by the intensity of light irradiation and was saturated under the higher voltage regions. Up-converted light emission was also observed under the light irradiation.

Configuration regulation of active sites by accurate doping inducing self-adapting defect for enhanced photocatalytic applications: A review

Magneto-optical investigation of flux penetration into high-temperature superconducting thin films allows the determination of the local critical current density ${j}_{c}$ by an inversion scheme of Biot-Savart's law. This method is used to examine the influence of silver sheeting on ${j}_{c}$ in thin films of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (YBCO) quantitatively. It can be found that a feasible silver covering layer on top of a YBCO thin film can enhance the critical current density by up to 50%. Spatially resolved measurements of the magnetic-flux density distribution in partly silver covered YBCO films show the influence of the cover layer on the current pattern in the superconductor. The measured enhancement of the critical current density, that is induced by the silver layer, has its origin in a spatially varying proximity effect between superconductor and silver layer which leads to a strong variation of the flux-line energies on a small length scale. This variation is directly related to an additional pinning force density on the flux lines. A detailed model is developed that can explain the measured enhancement of the critical current density by considering this additional pinning.

Enhancements of critical current density in Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductors by additions of SnO2 nanoparticles

Enhancement of critical current density in fast neutron irradiated melt-textured YBa 2Cu 3O 7- x

Enhancement of critical current density in glycine-doped MgB2 bulks