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The uniform and continuous nickel internal electrode is crucial in high capacity and highly reliable multi-layer ceramic capacitors (MLCCs). However, the mechanism and the key factors that affect the roughness of the electrode have not been investigated thoroughly. Thus, seeking suitable descriptors that describe the most influential element which decides the roughness is required for the logical design of the Ni paste. In this study, we analyzed the surface of nickel powders and compared their electrode roughness in the aspects of the surface carbon species on nickel nanoparticles. As the increase in the relative C–O/C–C and C=O/C–C ratios, the relative electrode roughness of C-Ni-1, C-Ni-2, C-Ni-3, and C-Ni-4 increased from 1.00, 1.29, 1.54 to 2.51. Thus, low contents of C–O and C=O on the surface of Ni particles could improve the uniformity of the electrode. This study suggests a valuable perspective to reveal the decisive component to build the optimum surface of nickel nanoparticles for uniform internal electrodes in MLCCs.

Despite their high theoretical energy density, lithium-oxygen (Li−O2) batteries suffer from limited cyclability originating from poor charging efficiency. In an effort to overcome this critical issue, a variety of catalysts have been introduced, but much room still remains for further advancement in catalyst design. By benchmarking hemoglobin in red blood cells that carry oxygen at a well-defined center of the molecular cage, herein, we report heme as an air-cathode catalyst with iron (Fe) active sites. Furthermore, the coordination of electron-withdrawing ligands, such as thiocyanate (S C N) and azide (N3), to the Fe center enhances its Lewis acidity to weaken the binding of oxygen intermediates (O2∗) towards more facile decomposition of the main discharging product (Li2O2). Density functional theory calculations and surface energy analysis of Fe coherently support the advantageous role of the ligand engineering in enhancing the reversibility of a Li−O2 battery.

In this research, environmental fate modeling (EFM) was studied to evaluate exposed lead-containing compounds in PSCs and their impact on the environment and on humans. Two major accidental situations involving the environment and exposure to compounds were considered plausible scenarios: fire (PbO) and flooding (PbI2). As a result, water systems were deemed the most vulnerable to the toxicity of exposure to lead compounds. In conclusion, the effect of various environmental and human factors should be assessed and safety standards should be established using the most conservative range among various environmental evaluation results.

The high specific capacity in excess of 200 mAh g-1 and low dependence on cobalt have enhanced the research interest on nickel-rich layered metal oxides as cathode materials for lithium-ion batteries for electric vehicles. Nonetheless, their poor cycle life and thermal stability, resulting from the occurrence of cation mixing between the transition-metal (TM) and lithium ions, are yet to be fully addressed to enable the widespread and reliable use of these materials. Here, we report a two-dimensional (2D) pyrazine-linked covalent organic framework (namely, Pyr-2D) as a coating material for nickel-rich layered cathodes to mitigate unwanted TM dissolution and interfacial reactions. The Pyr-2D coating layer, especially the 2D planar morphology and conjugated atomic configuration of Pyr-2D, protects the electrode surface effectively during cycling without sacrificing the electric conductivity of the host material. As a result, Pyr-2D-coated nickel-rich layered cathodes exhibited superior cyclability, rate performance, and thermal stability. The present study highlights the potential ability of 2D conjugated covalent organic frameworks to improve the key electrochemical properties of emerging battery electrodes.

Mn5O8 nanoparticles (NPs) were obtained via the controlled oxidation of MnO NPs. The oxygen evolution reaction (OER) properties of Mn5O8 NPs were evaluated using cyclic voltammetry (CV). A current density of 5 mA/cm2 was reached when 580 mV of overpotential was applied at pH 7.8. Electron paramagnetic resonance (EPR) analysis was conducted to investigate the origin of high OER activity of Mn5O8 NPs. From the EPR analysis, Mn3+ was found to be involved in the OER process of the Mn5O8 materials.

Photoelectrochemical hydrogen production from solar energy has been attracting much attention in the field of renewable energy technology. The realization of cost-effective hydrogen production by water splitting requires electrolysis or photoelectrochemical cells decorated with highly efficient co-catalysts. A critical requirement for catalysts in photoelectrochemical cells is not only the ability to boost the kinetics of a chemical reaction but also to exhibit durability against electrochemical and photoinduced degradation. In the race to replace previous noble-metal catalysts, the design of carbon-based catalysts represents an important research direction in the search for non-precious, environmentally benign, and corrosion-resistant catalysts. Herein, we suggest graphene quantum sheets as a catalyst for the solar-driven hydrogen evolution reaction on Si nanowire photocathodes. The optimum nanostructures of the Si photocathodes exhibit an enhanced photocurrent and a lower overpotential compared to those of a planar Si surface. This significant enhancement demonstrates how graphene quantum sheet catalysts can be used to produce Si nanowire photocathodes as hydrogen evolution reaction catalysts with high activity.

The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt- and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (∼0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry., The role of metal-coordination environment on the effectiveness of water oxidation catalysts is relatively unexplored. Here, the authors study a range of cobalt phosphate catalysts with varying coordination environments and observe high activity and stability for a distorted tetrahedral cobalt system.

The oxygen evolution reaction (OER) is considered a major bottleneck in the overall water electrolysis process. In this work, highly active manganese oxide nano-catalysts were synthesized via hot injection. Facile surface treatment generated Mn(III) species on monodisperse 10 nm MnO nanocrystals (NCs). Size dependency of MnO NCs on OER activity was also investigated. Surprisingly, the partially oxidized MnO NCs only required 530 mV @ 5 mA cm−2 under near neutral conditions.

According to the Dollo’s law, biological evolution that authorize a species new functions, simultaneously create a mechanical or physiological limitations. This perspective has been also applicable to technological innovation, and energy storage systems have seemed to strictly obey the rules. Rigid external passive structures have been thought to be essential for the conventional energy storage systems, because packaging with robust wearing maintain the structure of a device and minimize damages that are caused by impacts from external forces and the environment. However, these advantageous characteristics of conventional device packaging results in critical limitations for further innovation of energy storage systems, such as (1) low degree of deformation, (2) scalability of device unit and (3) thermal and pressure controllability. As the vertebrates blazed a trail in the biological evolution with endoskeleton frame, we propose a novel construction of energy storage device with an analogy to bio-systems. Reverse stacking to fabricate endoskeletal frame would allow energy storage devices deformable and consequently applicable to diverse electronics with generosity.

Correction for ‘N-doped graphene quantum sheets on silicon nanowire photocathodes for hydrogen production’ by Uk Sim et al., Energy Environ. Sci., 2015, DOI: 10.1039/c4ee03607g.