Abstract More active electrocatalysts for H 2 and O 2 evolution reactions, efficient membranes, and robust porous transport layers (PTL) are required for designing advanced proton exchange membrane water electrolysis (PEMWE) systems. An N‐doped carbon matrix is introduced in this study to surpass the existing Ti PTLs. One‐step pyrolysis results in the carbonization of polyaniline films to the N‐doped carbon matrix, simultaneous formation of desiccation cracks and Ir x Ru y nanoparticles, and partial impregnation of the synthesized particles into the carbon matrix. The embedded Ir x Ru y nanoparticles are firmly bound to the surface of the carbon matrix, inhibiting the dissolution and detachment of the nanoparticles during the O 2 evolution reaction (OER). The cracks in the carbon matrix allow the steady transport of the produced O 2 , comparable to conventional PTLs. After optimizing the Ir and Ru contents of the nanoparticles based on the electrocatalytic performance, Ir 88 Ru 12 embedded in the N‐doped carbon matrix is found to be the most suitable catalyst for enhancing the OER performance of the PEMWE system with negligible degradation. These findings can potentially contribute to the industrial application of PEMWE. Relevant electrochemical systems with membrane electrode assemblies, such as fuel cells and CO 2 reduction systems, can be modified using the suggested structure.
Palladium nanoparticles with a N-doped carbon shell are made through an aniline-palladium redox reaction and heat treatment, enhancing stability and performance in fuel cells by preventing palladium dissolution.
The recent COVID-19 pandemic has been disrupting the daily lives of people across the world, causing a major concern for psychological well-being in children. This study aimed to examine (1) how life satisfaction and its potential predictors have been affected by the pandemic among school-aged children in Korea, and (2) which factors would predict their life satisfaction during the pandemic. We surveyed 166 fourth-graders in the Seoul metropolitan area to assess their psychological well-being and potentially related variables during the pandemic. The data were compared with those available from two pre-COVID-19 surveys, the 2018 Korean Children and Youth Panel Survey (n = 1236) and the 2019 Korean Children and Youth Well-being Index Survey (n = 334). Higher levels of stress were observed in children during the COVID-19 pandemic; however, the level of their life satisfaction remained unchanged when compared with data from the pre-COVID-19 surveys. The pandemic also affected peer relationship quality and susceptibility to smartphone addiction, but not perceived parenting style nor academic engagement. Interestingly, peer relationship quality no longer predicted life satisfaction during the pandemic; perceived parenting styles and parent-child conversation time predicted life satisfaction. The results suggest a central role of parent-child relationship in supporting the psychological well-being of school-aged children during the pandemic.
A promising route has been employed to prepare nickel nanoparticles encapsulated by carbon shell with enhanced catalytic activity and durability for electro-oxidation of urea.
Abstract Proton exchange membrane water electrolysis (PEMWE) emerges as a promising avenue for storing excess renewable energy by generating H 2 gas without introducing additional carbon emissions. However, PEMWE systems still grapple with challenges related to energy efficiency, cell longevity, and maximum operational current density. Consequently, extensive research efforts have been directed toward enhancing the performance of electrocatalysts and refining system designs to overcome these limitations. Within this framework, this study introduces a novel synthetic approach for fabricating N‐doped carbon matrices with a checkered pattern on the surface of porous transport layers (PTLs) composed of titanium (Ti). The resulting N‐doped checkered carbon matrices serve as robust hosts for Ir‐Ru nanoparticles during the oxygen evolution reaction (OER), ensuring their stable integration. Additionally, the checkered pattern of the N‐doped carbon matrices facilitates the efficient transport of both electrolyte and produced O 2 gas. Capitalizing on these advantages, the incorporation of checkered carbon matrices with Ir‐Ru nanoparticles has achieved a cell current density of 6.82 A cm −2 at a unit cell voltage of 2.0 V. The benefits of this structural innovation extend beyond water electrolysis and can be extrapolated to other electrochemical systems involving the production and transport of gas bubbles, such as CO 2 reduction.
The urea oxidation reaction (UOR) has been recognized as a potential replacement for the hydrogen oxidation reaction in anion exchange membrane fuel cells. For the successful application of this technology, advanced electrocatalysts for UOR must be developed to overcome the high overpotential. This can be achieved by introducing Co into Ni-based catalysts. Normally, an optimum ratio of Ni:Co would show the highest activity; however, a higher content of Co adversely affects the catalyst performance. In this study, we provide an explanation for the optimum point in NiCo-based catalysts. In addition to the positive effect of reducing the UOR onset potential, electrochemical analyses suggested that an electro-inactive species for UOR was formed by doping with Co, and this species exerted its influence more strongly as the content of Co increased. Thus, the performance was maximized at an optimum ratio of Ni:Co, at which the advantages and disadvantages of Co-doping were balanced. The results of our study indicated that Co-doping around 5-10 at% showed the highest UOR catalytic activity, as proven by half-cell and unit-cell tests.
Enwrapping metal nanoparticles with a carbon shell is a promising method for enhancing the stability of metal catalysts. However, carbon shell thickness control has not been studied extensively. In this study, a Pt catalyst with a carbon shell was synthesized, and the thickness of the carbon shell was controlled via the partial oxidation of the carbon layer. During the cooling step of the carbonization process, various concentrations of oxygen were supplied, and changes in the layer thickness were investigated according to the oxygen concentration. The thickness and characteristics of the carbon shell were examined using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The results revealed that the thickness and surface properties of the carbon layer depend on the oxygen concentration. To determine the effect of the carbon shell thickness on the electrochemical characteristics of the catalyst, the activity and durability of the catalyst were studied via an oxygen reduction reaction and an accelerated stress test in both a half-cell and unit cell. Overall, the thin carbon shell enabled the Pt catalyst to maintain its activity and stability, while reducing the activation time required to achieve optimal performance.
Encapsulating platinum nanoparticles with a carbon shell can increase the stability of core platinum nanoparticles by preventing their dissolution and agglomeration. In this study, the synthesis mechanism of a platinum core-carbon shell catalyst via thermal reduction of a platinum-aniline complex was investigated to determine how the carbon shell forms and identify the key factor determining the properties of the Pt core-carbon shell catalyst. Three catalysts originating from the complexes with different platinum to carbon precursor ratios were synthesized through pyrolysis. Their structural characteristics were examined using various analysis techniques, and their electrochemical activity and stability were evaluated through half-cell and unit-cell tests. The relationship between the nitrogen to platinum ratio and structural characteristics was revealed, and the effects on the electrochemical activity and stability were discussed. The ratio of the carbon precursor to platinum was the decisive factor determining the properties of the platinum core-carbon shell catalyst.
'%3e%3cg id='b'%3e%3cpath id='a' stroke='%23000' stroke-width='2' d='M-6-25H6m-12 3H6m-12 3H6'/%3e%3cuse xlink:href='%23a' y='44'/%3e%3c/g%3e%3cpath stroke='%23fff' d='M0 17v10'/%3e%3ccircle r='12' fill='%23cd2e3a'/%3e%3cpath fill='%230047a0' d='M0-12A6 6 0 0 0 0 0a6 6 0 0 1 0 12 12 12 0 0 1 0-24z'/%3e%3c/g%3e%3cg transform='rotate(-123.69)'%3e%3cuse xlink:href='%23b'/%3e%3cpath stroke='%23fff' d='M0-23.5v3M0 17v3.5m0 3v3'/%3e%3c/g%3e%3c/svg%3e)