Thermodynamic phase control of Cu-Sn alloy electrocatalysts for selective CO2 reduction.

In the electrochemical CO2 reduction reaction (CO2RR), Cu alloy electrocatalysts can control the CO2RR selectivity by modulating the intermediate binding energy. Here, we report the thermodynamic-based Cu-Sn bimetallic phase control in heterogeneous catalysts for selective CO2 conversion. Starting from the thermodynamic understanding about Cu-Sn bimetallic compounds, we established the specific processing window for Cu-Sn bimetallic phase control. To modulate the Cu-Sn bimetallic phases, we controlled the oxygen partial pressure (pO2) during the calcination of electrospun Cu and Sn ions-incorporated nanofibers (NFs). This resulted in the formation of CuO-SnO2 NFs (full oxidation), Cu-SnO2 NFs (selective reduction), Cu3Sn/CNFs, Cu41Sn11/CNFs, and Cu6Sn5/CNFs (full reduction). In the CO2RR, CuO-SnO2 NFs exhibited formate (HCOO-) production and Cu-SnO2 NFs showed carbon monoxide (CO) production with the faradaic efficiency (FE) of 65.3% at -0.99 V (vs. RHE) and 59.1% at -0.89 V (vs. RHE) respectively. Cu-rich Cu41Sn11/CNFs and Cu3Sn/CNFs enhanced the methane (CH4) production with the FE of 39.1% at -1.36 V (vs. RHE) and 34.7% at -1.50 V (vs. RHE). However, Sn-rich Cu6Sn5/CNFs produced HCOO- with the FE of 58.6% at -2.31 V (vs. RHE). This study suggests the methodology for bimetallic catalyst design and steering the CO2RR pathway by controlling the active sites of Cu-Sn alloys.

A Mask-Shaped Respiration Sensor Using Triboelectricity and a Machine Learning Approach toward Smart Sleep Monitoring Systems.

Daily sleep monitoring is limited by the needs for specialized equipment and experts. This study combines a mask-shaped triboelectric nanogenerator (M-TENG) and machine learning for facile daily sleep monitoring without the specialized equipment or experts. The fabricated M-TENG demonstrates its excellent ability to detect respiration, even distinguishing oral and nasal breath. To increase the pressure sensitivity of the M-TENG, the reactive ion etching is conducted with different tilted angles. By investigating each surface morphology of the polytetrafluoroethylene films according to the reactive ion etching with different tilted angles, the tilted angle is optimized with the angle of 60° and the pressure sensitivity is increased by 5.8 times. The M-TENG can also detect changes in the angle of head and snoring. Various sleep stages can be classified by their distinctive electrical outputs, with the aid of a machine learning approach. As a result, a high averaged-classification accuracy of 87.17% is achieved for each sleep stage. Experimental results demonstrate that the proposed combination can be utilized to monitor the sleep stage in order to provide an aid for self-awareness of sleep disorders. Considering these results, the M-TENG and machine learning approach is expected to be utilized as a smart sleep monitoring system in near future.

Robust Co alloy design for Co interconnects using a self-forming barrier layer.

With recent rapid increases in Cu resistivity, RC delay has become an important issue again. Co, which has a low electron mean free path, is being studied as beyond Cu metal and is expected to minimize this increase in resistivity. However, extrinsic time-dependent dielectric breakdown has been reported for Co interconnects. Therefore, it is necessary to apply a diffusion barrier, such as the Ta/TaN system, to increase interconnect lifetimes. In addition, an ultrathin diffusion barrier should be formed to occupy as little area as possible. This study provides a thermodynamic design for a self-forming barrier that provides reliability with Co interconnects. Since Cr, Mn, Sn, and Zn dopants exhibited surface diffusion or interfacial stable phases, the model constituted an effective alloy design. In the Co-Cr alloy, Cr diffused into the dielectric interface and reacted with oxygen to provide a self-forming diffusion barrier comprising Cr2O3. In a breakdown voltage test, the Co-Cr alloy showed a breakdown voltage more than 200% higher than that of pure Co. The 1.2 nm ultrathin Cr2O3 self-forming barrier will replace the current bilayer barrier system and contribute greatly to lowering the RC delay. It will realize high-performance Co interconnects with robust reliability in the future.

Difference in home participation patterns and environmental factors between Korean children with and without disabilities.

PURPOSE: To identify the participation patterns of Korean children with and without disabilities at home, and the environmental factors affecting their participation. MATERIALS AND METHODS: The Korean Participation and Environment Measure for Children and Youth were applied to 184 caregivers of children aged 5 to 13 years in South Korea. To explore home participation patterns and environmental factors at the item level, analysis of covariance, Pearson's chi-square tests, and radar plots were used. RESULTS: The largest group differences in participation frequency were in "school preparation" and "homework" and those at involvement level were in "indoor play and games," "getting together with other people," "school preparation," and "homework." More caregivers of children with disabilities desired changes in their children's participation in all activities. They also perceived that "physical, cognitive, and social demands of typical home activities," "supplies," and "money" hindered children's home participation. CONCLUSIONS: The findings provide information about how Korean children participated in home-based activities, whether their caregivers desired changes in their participation, and what environmental factors impede their home participation. These can help service providers understand the interaction between participation and environmental factors and offer insight into where their service goals should be focused for the successful participation of children with disabilities at home.Implications for RehabilitationAs children with disabilities spend much time at home, their parents need to consider both how many times their children participate and how much they get involved in home-based activities.Rehabilitation service providers need to focus on whether parents are satisfied with their children's participation in home activities to decide where much effort is needed for meaningfully occupying children's time at home.The goal of rehabilitation services can be to mitigate a poor fit between children's abilities and the demands of activities for successful participation in home activities.Measuring not only the quantity of participation but also the quality of participation is helpful for setting a collaborative goal with parents to improve the participation of children with disabilities at home.

Phase Engineering of Transition Metal Dichalcogenides via a Thermodynamically Designed Gas-Solid Reaction.

Polymorph conversion of transition metal dichalcogenides (TMDs) offers intriguing material phenomena that can be applied for tuning the intrinsic properties of 2D materials. In general, group VIB TMDs can have thermodynamically stable 2H phases and metastable 1T/T' phases. Herein, we report key principles to apply carbon monoxide (CO)-based gas-solid reactions for a universal polymorph conversion of group VIB TMDs without forming undesirable compounds. We found that the process conditions are strongly dependent on the reaction chemical potential of cations in the TMDs, which can be predicted by thermodynamic calculations, and that polymorphic conversion is triggered by S vacancy (VS) formation. Furthermore, we conducted DFT calculations for the reaction barriers of VS formation and S diffusion to reveal the polymorph conversion mechanism of WS2 and compared it with that of MoS2. We believe that phase engineering 2D materials via thermodynamically designed gas-solid reactions could be functionally used to achieve defect-related nanomaterials.

Quasi-graphitic carbon shell-induced Cu confinement promotes electrocatalytic CO2 reduction toward C2+ products.

For steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas-solid reaction governed by the CO (g) - CO2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO2 reduction reaction and provided a platform for rational material design. C2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C2H4 at -0.55 V (vs RHE) and a C2H4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO2-to-C2H4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion.

Psychometric properties of the Korean Motor-free Visual Perception Test-4 in healthy people.

OBJECTIVE: This study was conducted to cross-culturally adapt the Motor-free Visual Perception Test 4 (MVPT-4) for use in Korean contexts and examine its psychometric properties. METHODS: The Korean MVPT-4 (K-MVPT-4) was developed via the process of translation, back-translation, and expert committee review. To establish internal consistency, test-retest reliability, concurrent validity and construct validity of the K-MVPT-4, 295 healthy people aged 10 to 79 years participated in this study. Participants completed the measures for the test-retest reliability on two occasions, 2 weeks apart. RESULTS: After three steps of cross-cultural adaptation, the K-MVPT-4 was revised to improve its alignment with Korean cultural norms. Cronbach's α for internal consistency was .857 and intra-class correlation coefficient for test-retest reliability was .949. The K-MVPT-4 scores were significantly correlated with those of three motor-reduced subscales of the Korean Developmental Test of Visual Perception-Adolescent (K-DTVP-A) (r = .44-.46, p < .01). Participants' age significantly influenced the K-MVPT-4 scores (p < .001) while their gender did not affect those scores (p = .409). As the age increased, the K-MVPT-4 scores decreased. CONCLUSIONS: The findings indicated that the K-MVPT-4 is a reliable and valid test that Korean rehabilitation service providers can use with confidence to assess clients' visual perceptual abilities.

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO2 reduction.

The electrochemical CO2 reduction reaction (CO2RR), which converts CO2 into value-added feedstocks and renewable fuels, has been increasingly studied as a next-generation energy and environmental solution. Here, we report that single-atom metal sites distributed around active materials can enhance the CO2RR performance by controlling the Lewis acidity-based local CO2 concentration. By utilizing the oxidation Gibbs free energy difference between silver (Ag), zinc (Zn), and carbon (C), we can produce Ag nanoparticle-embedded carbon nanofibers (CNFs) where Zn is atomically dispersed by a one-pot, self-forming thermal calcination process. The CO2RR performance of AgZn-CNF was investigated by a flow cell with a gas diffusion electrode (GDE). Compared to Ag-CNFs without Zn species (53% at -0.85 V vs. RHE), the faradaic efficiency (FE) of carbon monoxide (CO) was approximately 20% higher in AgZn-CNF (75% at -0.82 V vs. RHE) with 1 M KOH electrolyte.