The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial reactions in energy conversion and storage systems including fuel cells, metal–air batteries, and electrolyzers. ...Developing low‐cost, high‐efficiency, and durable non‐noble bifunctional oxygen electrocatalysts is the key to the commercialization of these devices. Here, based on an in‐depth understanding of ORR/OER reaction mechanisms, recent advances in the development of non‐noble electrocatalysts for ORR/OER are reviewed. In particular, rational design for enhancing the activity and stability and scalable synthesis toward the large‐scale production of bifunctional electrocatalysts are highlighted. Prospects and future challenges in the field of oxygen electrocatalysis are presented.
Low‐cost and efficient bifunctional oxygen electrocatalysts are key to the commercialization of reversible fuel cells, metal–air batteries and electrolyzers. Herein, recent advances in the development of non‐noble bifunctional oxygen reduction reaction/oxygen evolution reaction electrocatalysts toward large‐scale production are presented, together with a discussion of the future challenges and prospects in this field.
Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion‐exchange‐membrane fuel cells. However, uncertainty ...remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface‐enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OHad) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OHad species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum‐alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.
HOR on Au@PtNi surfaces in alkaline media has been investigated by in situ surface‐enhanced Raman spectroscopy (see picture). Direct spectroscopic evidence for OHad species was observed and further confirmed by deuterium isotopic experiments and DFT.
2D conductive metal–organic frameworks (2D c‐MOFs) feature promising applications as chemiresistive sensors, electrode materials, electrocatalysts, and electronic devices. However, exploration of the ...spin‐polarized transport in this emerging materials and development of the relevant spintronics have not yet been implemented. In this work, layer‐by‐layer assembly was applied to fabricate highly crystalline and oriented thin films of a 2D c‐MOF, Cu3(HHTP)2, (HHTP: 2,3,6,7,10,11‐hexahydroxytriphenylene), with tunable thicknesses on the La0.67Sr0.33MnO3 (LSMO) ferromagnetic electrode. The magnetoresistance (MR) of the LSMO/Cu3(HHTP)2/Co organic spin valves (OSVs) reaches up to 25 % at 10 K. The MR can be retained with good film thickness adaptability varied from 30 to 100 nm and also at high temperatures (up to 200 K). This work demonstrates the first potential applications of 2D c‐MOFs in spintronics.
2D c‐MOF based organic spin valves: Layer‐by‐layer assembly was applied to fabricate highly crystalline and oriented thin films of 2D conductive MOF, Cu3(HHTP)2, on the La0.67Sr0.33MnO3 (LSMO) ferromagnetic electrode. A large magnetoresistance of 25 % for this LSMO/Cu3(HHTP)2/Co organic spin valve was achieved. This work demonstrates promising applications of 2D c‐MOFs in spintronics.
Piezocatalysis is an emerging technique that holds great promise for the conversion of ubiquitous mechanical energy into electrochemical energy through piezoelectric effect. However, mechanical ...energies in natural environment (such as wind energy, water flow energy, and noise) are typically tiny, scattered, and featured with low frequency and low power. Therefore, a high response to these tiny mechanical energies is critical to achieving high piezocatalytic performance. In comparison to nanoparticles or 1D piezoelectric materials, 2D piezoelectric materials possess characteristics such as high flexibility, easy deformation, large surface area, and rich active sites, showing more promise in future for practical applications. In this review, state‐of‐the‐art research progresses on 2D piezoelectric materials and their applications in piezocatalysis are provided. First, a detailed description of 2D piezoelectric materials are offered. Then a comprehensive summary of the piezocatalysis technique is presented and examines the piezocatalysis applications of 2D piezoelectric materials in various fields, including environmental remediation, small‐molecule catalysis, and biomedicine. Finally, the main challenges and prospects of 2D piezoelectric materials and their applications in piezocatalysis are discussed. It is expected that this review can fuel the practical application of 2D piezoelectric materials in piezocatalysis.
2D piezoelectric materials constitute a promising alternative for piezocatalysis due to their inherent advantages, such as high flexibility, large surface area, and abundant active sites. In this review, the state‐of‐the‐art research progresses on 2D piezoelectric materials and their applications in piezocatalysis are summarized. The overall goal is to inspire and accelerate the practical deployment of 2D piezoelectric materials for piezocatalytic applications.
The study of the oxygen reduction reaction (ORR) at high-index Pt(hkl) single crystal surfaces has received considerable interest due to their well-ordered, typical atomic structures and superior ...catalytic activities. However, it is difficult to obtain direct spectral evidence of ORR intermediates during reaction processes, especially at high-index Pt(hkl) surfaces. Herein, in situ Raman spectroscopy has been employed to investigate ORR processes at high-index Pt(hkl) surfaces containing the 011̅ crystal zonei.e., Pt(211) and Pt(311). Through control and isotope substitution experiments, in situ spectroscopic evidence of OH and OOH intermediates at Pt(211) and Pt(311) surfaces was successfully obtained. After detailed analysis based on the Raman spectra and theoretical simulation, it was deduced that the difference in adsorption of OOH at high-index surfaces has a significant effect on the ORR activity. This research illuminates and deepens the understanding of the ORR mechanism on high-index Pt(hkl) surfaces and provides theoretical guidance for the rational design of high activity ORR catalysts.
Background: Several studies have reported that mindfulness meditation has a potential effect in controlling headaches, such as migraine and tension-type headache; however, its role remains ...controversial. This review assessed the evidence regarding the effects of mindfulness meditation for primary headache pain.
Methods: Only English databases (PubMed, Cochrane Central Register of Controlled Trials the Cochrane Library, PsycINFO, Psychology and behavioral science collection, PsyArticles, Web of Science, and Scopus) were searched from their inception to November 2016 with the keywords ("meditation" or "mindfulness" or "vipassana" or "dzogchen" or "zen" or "integrative body-mind training" or "IBMT" or "mindfulness-based stress reduction" or "MBSR" or "mindfulness-based cognitive therapy" or "MBCT" and "Headache" or "Head pain" or "Cephalodynia" or "Cephalalgia" or "Hemicrania" or "Migraine"). Titles, abstracts, and full-text articles were screened against study inclusion criteria: controlled trials of structured meditation programs for adult patients with primary headache pain. The quality of studies included in the meta-analysis was assessed with the Yates Quality Rating Scale. The meta-analysis was conducted with Revman 5.3.
Results: Ten randomized controlled trials and one controlled clinical trial with a combined study population of 315 patients were included in the study. When compared to control group data, mindfulness meditation induced significant improvement in pain intensity (standardized mean difference, −0.89; 95% confidence interval, −1.63 to −0.15; P = 0.02) and headache frequency (−0.67; −1.24 to −0.10; P = 0.02). In a subgroup analysis of different meditation forms, mindfulness-based stress reduction displayed a significant positive influence on pain intensity (P < 0.000). Moreover, 8-week intervention had a significant positive effect (P < 0.000).
Conclusions: Mindfulness meditation may reduce pain intensity and is a promising treatment option for patients. Clinicians may consider mindfulness meditation as a viable complementary and alternative medical option for primary headache.
The rapid recombination of photogenerated electrons and holes greatly limits the efficiency of photocatalyst based on semiconductor. In order to address this issue, we predicted a novel ferroelectric ...polarized heterojunction photocatalyst, CdS/In2Se3, which enables the spontaneous overall water splitting reaction. The CdS/In2Se3 heterojunction exhibits a band-edge staggered alignment and it is easy to form a direct Z-scheme charge transfer pathway. Besides, the built-in electric field (Eint) in the CdS/In2Se3 heterojunction promoted the charge transfer of CdS/In2Se3, leading to an improved separating efficiency of photo-generated carriers. Moreover, the vertical intrinsic polarized electric field (Ep) not only alters the position of the band edge but also reduces the bandgap limitations commonly associated with photocatalytic materials. Furthermore, the CdS/In2Se3 heterojunctions demonstrate separate catalytic activity for the hydrogen evolution reaction (HER) on the surface of the CdS monolayer and oxygen evolution reaction (OER) on the surface of In2Se3, respectively. Notably, the CdS/In2Se3-down configuration enables spontaneous photocatalytic water splitting in pH = 7, while the CdS/In2Se3-up configuration efficiently facilitates the HER process. This study highlights the significant advantages of CdS/In2Se3 heterojunctions as photocatalytic materials, offering unique insights into the development and research of this promising heterojunction architecture.
Notch and size effects generally show great influence on the fatigue behavior of engineering structures, which plays a vital role during their structural integrity and reliability evaluations. In ...this study, the influence of notch size effect on fatigue life and critical distance values were investigated. Particularly, a novel method for fatigue life distribution assessment of notched specimens was proposed based on Weibull model and critical distance theory. Experimental data of Al 2024-T351 smooth plate specimens and center hole plate (CHP) specimens with four different notch radii were utilized for model validation and comparison. Results show that all predicted lives of Al 2024-T351 CHP specimens are within the ±2 life scatter bands of experimental ones.
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•Weibull model describes well the dispersity of fatigue lives of Al 2024-T351 alloys.•Influence of notch size effect on critical distance and fatigue strength were characterized.•Proposed model by coupling Weibull with critical distance theories for considering notch size effect.•Proposed model predictions of Al 2024-T351 center hole plate specimens are within ±2 life scatter bands of experimental ones.
Investigating the chemical nature of the adsorbed intermediate species on well-defined Cu single crystal substrates is crucial in understanding many electrocatalytic reactions. Herein, we ...systematically study the early stages of electrochemical oxidation of Cu(111) and polycrystalline Cu surfaces in different pH electrolytes using in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). On Cu(111), for the first time, we identified surface OH species which convert to chemisorbed “O” before forming Cu2O in alkaline (0.01 M KOH) and neutral (0.1 M Na2SO4) electrolytes; while at the Cu(poly) surface, we only detected the presence of surface hydroxide. Whereas, in a strongly acidic solution (0.1 M H2SO4), sulfate replaces the hydroxyl/oxy species. This results improves the understanding of the reaction mechanisms of various electrocatalytic reactions.
Precise control and accurate understanding of the ordering degree of bimetallic nanocatalysts (BNs) are challenging yet crucial to acquire advanced materials for the oxygen reduction reaction (ORR). ...AuCu BNs with various ordering degrees were synthesized to evaluate the influence of ordering degree on the ORR at a molecular level using in situ Raman spectroscopy. The activity of AuCu BNs was improved by over 2 times after a disorder‐to‐order transition, making the performance of highly ordered AuCu BNs exceed that of benchmark Pt/C. Direct Raman spectroscopic evidence of key intermediate (*OH) demonstrates that the active site is the combination site of Au and Cu. Moreover, two distinct *OH species are observed on the ordered and disordered structure, and the ordered site is more beneficial for ORR due to its lower affinity to *OH. This work deepens the understanding on the important role of ordering degree on BNs and enables the design of improved catalysts.
The critical role of the ordering degree of AuCu bimetallic catalysts was studied in situ by a shell‐isolated nanoparticle‐enhanced Raman spectroscopy satellite strategy and the molecular reaction mechanism is revealed.
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