Over the past few decades, development of electrocatalysts for energy applications has extensively transitioned from trial-and-error methodologies to more rational and directed designs at the atomic ...levels via either nanogeometric optimization or modulating electronic properties of active sites. Regarding the modulation of electronic properties, nonprecious transition metal-based materials have been attracting large interest due to the capability of versatile tuning d-electron configurations expressed through the flexible orbital occupancy and various possible degrees of spin polarization. Herein, recent advances in tailoring electronic properties of the transition-metal atoms for intrinsically enhanced electrocatalytic performances are reviewed. We start with discussions on how orbital occupancy and spin polarization can govern the essential atomic level processes, including the transport of electron charge and spin in bulk, reactive species adsorption on the catalytic surface, and the electron transfer between catalytic centers and adsorbed species as well as reaction mechanisms. Subsequently, different techniques currently adopted in tuning electronic structures are discussed with particular emphasis on theoretical rationale and recent practical achievements. We also highlight the promises of the recently established computational design approaches in developing electrocatalysts for energy applications. Lastly, the discussion is concluded with perspectives on current challenges and future opportunities. We hope this review will present the beauty of the structure–activity relationships in catalysis sciences and contribute to advance the rational development of electrocatalysts for energy conversion applications.
Developing highly efficient multifunctional electrocatalysts is crucial for future sustainable energy pursuits, but remains a great challenge. Herein, a facile synthetic strategy is used to confine ...atomically thin Pd–PdO nanodomains to amorphous Ru metallene oxide (RuO2). The as‐synthesized electrocatalyst (Pd2RuOx‐0.5 h) exhibits excellent catalytic activity toward the pH‐universal hydrogen evolution reaction (η10 = 14 mV in 1 m KOH, η10 = 12 mV in 0.5 m H2SO4, and η10 = 22 mV in 1 m PBS), alkaline oxygen evolution reaction (η10 = 225 mV), and overall water splitting (E10 = 1.49 V) with high mass activity and operational stability. Further reduction endows the material (Pd2RuOx‐2 h) with a promising alkaline oxygen reduction activity, evidenced by high halfway potential, four‐electron selectivity, and excellent poison tolerance. The enhanced catalytic activity is attributed to the rational integration of favorable nanostructures, including 1) the atomically thin nanosheet morphology, 2) the coexisting amorphous and defective crystalline phases, and 3) the multi‐component heterostructural features. These structural factors effectively regulate the material's electronic configuration and the adsorption of intermediates at the active sites for favorable reaction energetics.
Direct heterostructure engineering on an ultrathin 2D platform of Pd–PdO nanodomains confined on amorphous RuO2 yields excellent catalytic activity toward pH‐universal HER, alkaline oxygen electrochemistry, and overall water splitting. The enhanced multifunctional performance is attributed to the rational integration of novel nanostructures, including atomically thin morphology, coexisting amorphous and defect‐rich crystalline phases, and multicomponent heterostructural features.
In recent decades, significant progress has been achieved in rational developments of electrocatalysts through constructing novel atomistic structures and modulating catalytic surface topography, ...realizing substantial enhancement in electrocatalytic activities. Numerous advanced catalysts were developed for electrochemical energy conversion, exhibiting low overpotential, high intrinsic activity, and selectivity. Yet, maintaining the high catalytic performance under working conditions with high polarization and vigorous microkinetics that induce intensive degradation of surface nanostructures presents a significant challenge for commercial applications. Recently, advanced
operando
and computational techniques have provided comprehensive mechanistic insights into the degradation of surficial functional structures. Additionally, various innovative strategies have been devised and proven effective in sustaining electrocatalytic activity under harsh operating conditions. This review aims to discuss the most recent understanding of the degradation microkinetics of catalysts across an entire range of anodic to cathodic polarizations, encompassing processes such as oxygen evolution and reduction, hydrogen reduction, and carbon dioxide reduction. Subsequently, innovative strategies adopted to stabilize the materials' structure and activity are highlighted with an in-depth discussion of the underlying rationale. Finally, we present conclusions and perspectives regarding future research and development. By identifying the research gaps, this review aims to inspire further exploration of surface degradation mechanisms and rational design of durable electrocatalysts, ultimately contributing to the large-scale utilization of electroconversion technologies.
Unprecedented insights into electrochemical surface dynamics from
operando
studies inspire electronic and topographical strategies, paving the way for sustained electrocatalytic performance across HER, OER, ORR, and CO
2
RR applications.
Designing efficient bifunctional electrocatalysts with excellent activity and robust stability presents a central challenge for the large‐scale commercialization of water electrolysis. Herein, a ...facile approach is reported for the construct of atomically thin amorphous RuM (MCo, Fe, or Ni) bimetallenes as high‐performance electrocatalysts toward both electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The RuCo bimetallene manifests excellent bifunctional activity characterized by low required overpotentials, superior price activity, robust electrochemical durability as well as a low cell potential water splitting performance, outperforming Pt/C and RuO2 benchmark catalysts. Combined operando X‐ray absorption spectroscopy investigation and theoretical simulations reveal the synergism taking place between binary constituents, in which Co serves a promotive role along the HER/OER reaction pathway, contributing via optimal binding to *OH for facile water dissociation as well as modulating the Ru electronic structure favorably, hence rendering high activity catalytic centers for both the alkaline HER and OER.
Integrating oxophilic Co into Ru amorphous bimetallene realizes excellent bifunctional hydrogen evolution reaction and oxygen evolution reaction catalytic activity in an alkaline medium. Operando X‐ray absorption spectroscopy and theoretical studies reveal an energy‐favorable synergistic mechanism taking place on the electrocatalytic surface, in which Co functions as a promoter, enhancing the water adsorption and dissociation and optimizing the electron configuration of Ru sites, boosting the catalytic activity.
Hysteresis manifestation of graded rubber Do, Quoc‐Viet; Yamaguchi, Masayuki; Washizu, Kensuke ...
Polymers for advanced technologies,
January 2024, 2024-01-00, 20240101, Letnik:
35, Številka:
1
Journal Article
Recenzirano
In the present study, hysteresis loss in the cyclic stress–strain curves of graded styrene–butadiene rubber (SBR) was compared with that of homogenously crosslinked SBR. The graded SBR was prepared ...by vulcanization in a temperature gradient, which provided a gradient of crosslink density in the thickness direction of the sheet. The graded SBR had a higher hysteresis loss ratio than the homogenously crosslinked SBR, even though they had similar Young's moduli. The large energy loss must be attributed to the viscous response of the low‐crosslink‐density side of the rubber sheet. After the unloading process, the graded rubber exhibited a large instantaneous residual strain. However, its actual residual strain was small after waiting for a long time, indicating good rubber elasticity, which was attributed to the elastic response of the high‐crosslink‐density side of the rubber.
Engineering precious metals’ sub‐nanometer cluster on 2D earth‐abundant supports provides a promising approach for the development of high‐efficient electrocatalysts in pursuit of green ...hydrogen. Herein, a novel solid phase deposition approach is demonstrated for the homogenous confinement of atomically thin Pt nanoclusters on 2D delta‐MoN as a viable catalyst for pH‐universal hydrogen evolution reaction. Notably, the optimized material (MoN‐5% Pt) exhibits excellent catalytic performance as evidenced by low overpotentials required, excellent mass activity exceeding 20 A mgPt−1 at 100 mV overpotential, and outstanding stability with negligible activity degradation. The enhanced performance is attributed to (1) novel nanostructure, constituting atomically thin Pt nanoclusters confined on 2D δ‐MoN substrate, thus rendering high atomic utilization and seamless surface mass transfer, and (2) influence of strong metal‐support interaction that effectively limits structural deformation and performance degradation. Theoretical simulations reveal that the strong metal‐support interaction induces substantial charge redistribution across the heterointerface, initiating an energy‐favorable multi‐active site microkinetics in which Pt atoms with an optimal hydrogen adsorption energy making way for enhanced H2 evolution, while Mo atoms situated at the heterointerface enhance water absorption/dissociation steps, enriching the catalytic surface with adsorbed hydrogen atoms.
Confining atomically thin Pt nanoclusters on 2D δ‐MoN by virtue of strong metal‐support interaction (SMSI) enables an energetically favorable multi‐active site mechanism, resulting in outstanding pH‐universal hydrogen evolution reaction activity. The SMSI‐enhanced 2D ultrathin structure features seamless electronic and mass transports with minimal resistances and robust structural stability that render a durable catalytic performance under harsh operating conditions.
This study investigates how the level of board co-option might affect a borrowing firm's ex ante covenant intensity and ex post covenant violations. As the fraction of co-opted directors (those who ...joined the board after the CEO assumed office) increases, creditors include more covenant restrictions in their loan contracts, indicating that more co-opted boards are considered as weaker monitors. The results remain robust to various approaches accounting for endogeneity, and are not driven by alternative explanations such as CEO tenure, director inexperience, or CEO's involvement in the nominating committee. Ex post tests reveal that firms with more co-opted boards are more likely to violate loan covenants after controlling for covenant intensity. Non-co-opted independent directors appear to be the most effective monitors in mitigating covenant violations among revolving loans and loans to unrated borrowers.
•Creditors (banks) view co-opted directors as weaker monitors.•Borrowers with more co-opted boards face more loan covenant restrictions.•Borrowers with more co-opted boards are more likely to violate loan covenants.•Non-co-opted independent directors appear to be the most effective monitors.
Counterfeited products are costing the global economy hundreds of billions of dollars annually. Radio frequency identification(RFID) technology provides a promising solution for this problem, wherein ...each product is fitted with a secure tag, which is difficult to forge. However, RFID technology is faced with numerous security threats, for example, if the communication link between the reader and the tag is compromised, then it will be possible for a malicious adversary to obtain the private data stored on the device. Tag cloning attacks have also been demonstrated to be feasible, which severely undermines the capabilities of the RFID technology to protect against counterfeiting. One solution to this problem is the use of authentication protocol; however, existing schemes do not support mutual authentication and are still vulnerable to tag cloning attacks. In this article, a new security mechanism is proposed, which consists of a lightweight three-flights mutual authentication protocol and an anti-counterfeit tag design. The proposed solution is based on combining the Rabin public-key encryption scheme with physically unclonable functions (PUF) technology. The security of the proposed protocol is systematically analysed and compared with existing schemes. The implementation cost of the proposed security primitives, assuming the 1024-bit public key, is 10139 GEs, which is suitable for low-cost RFID tags. Our results show that the proposed design is up-to 50 percent more area-efficient compared to systems based on Elliptic Curve Cryptography (ECC).
SummaryBackgroundThe PORTEC-3 trial investigated the benefit of combined adjuvant chemotherapy and radiotherapy versus pelvic radiotherapy alone for women with high-risk endometrial cancer. We ...updated the analysis to investigate patterns of recurrence and did a post-hoc survival analysis. MethodsIn the multicentre randomised phase 3 PORTEC-3 trial, women with high-risk endometrial cancer were eligible if they had International Federation of Gynaecology and Obstetrics (FIGO) 2009 stage I, endometrioid grade 3 cancer with deep myometrial invasion or lymphovascular space invasion, or both; stage II or III disease; or stage I–III disease with serous or clear cell histology; were aged 18 years and older; and had a WHO performance status of 0–2. Participants were randomly assigned (1:1) to receive radiotherapy alone (48·6 Gy in 1·8 Gy fractions given on 5 days per week) or chemoradiotherapy (two cycles of cisplatin 50 mg/m 2 given intravenously during radiotherapy, followed by four cycles of carboplatin AUC5 and paclitaxel 175 mg/m 2 given intravenously), by use of a biased coin minimisation procedure with stratification for participating centre, lymphadenectomy, stage, and histological type. The co-primary endpoints were overall survival and failure-free survival. Secondary endpoints of vaginal, pelvic, and distant recurrence were analysed according to the first site of recurrence. Survival endpoints were analysed by intention-to-treat, and adjusted for stratification factors. Competing risk methods were used for failure-free survival and recurrence. We did a post-hoc analysis to analyse patterns of recurrence with 1 additional year of follow-up. The study was closed on Dec 20, 2013; follow-up is ongoing. This study is registered with ISRCTN, number ISRCTN14387080, and ClinicalTrials.gov, number NCT00411138. FindingsBetween Nov 23, 2006, and Dec 20, 2013, 686 women were enrolled, of whom 660 were eligible and evaluable (330 in the chemoradiotherapy group, and 330 in the radiotherapy-alone group). At a median follow-up of 72·6 months (IQR 59·9–85·6), 5-year overall survival was 81·4% (95% CI 77·2–85·8) with chemoradiotherapy versus 76·1% (71·6–80·9) with radiotherapy alone (adjusted hazard ratio HR 0·70 95% CI 0·51–0·97, p=0·034), and 5-year failure-free survival was 76·5% (95% CI 71·5–80·7) versus 69·1% (63·8–73·8; HR 0·70 0·52–0·94, p=0·016). Distant metastases were the first site of recurrence in most patients with a relapse, occurring in 78 of 330 women (5-year probability 21·4%; 95% CI 17·3–26·3) in the chemoradiotherapy group versus 98 of 330 (5-year probability 29·1%; 24·4–34·3) in the radiotherapy-alone group (HR 0·74 95% CI 0·55–0·99; p=0·047). Isolated vaginal recurrence was the first site of recurrence in one patient (0·3%; 95% CI 0·0–2·1) in both groups (HR 0·99 95% CI 0·06–15·90; p=0·99), and isolated pelvic recurrence was the first site of recurrence in three women (0·9% 95% CI 0·3–2·8) in the chemoradiotherapy group versus four (0·9% 95% CI 0·3–2·8) in the radiotherapy-alone group (HR 0·75 95% CI 0·17–3·33; p=0·71). At 5 years, only one grade 4 adverse event (ileus or obstruction) was reported (in the chemoradiotherapy group). At 5 years, reported grade 3 adverse events did not differ significantly between the two groups, occurring in 16 (8%) of 201 women in the chemoradiotherapy group versus ten (5%) of 187 in the radiotherapy-alone group (p=0·24). The most common grade 3 adverse event was hypertension (in four 2% women in both groups). At 5 years, grade 2 or worse adverse events were reported in 76 (38%) of 201 women in the chemoradiotherapy group versus 43 (23%) of 187 in the radiotherapy-alone group (p=0·002). Sensory neuropathy persisted more often after chemoradiotherapy than after radiotherapy alone, with 5-year rates of grade 2 or worse neuropathy of 6% (13 of 201 women) versus 0% (0 of 187). No treatment-related deaths were reported. InterpretationThis updated analysis shows significantly improved overall survival and failure-free survival with chemoradiotherapy versus radiotherapy alone. This treatment schedule should be discussed and recommended, especially for women with stage III or serous cancers, or both, as part of shared decision making between doctors and patients. Follow-up is ongoing to evaluate long-term survival. FundingDutch Cancer Society, Cancer Research UK, National Health and Medical Research Council, Project Grant, Cancer Australia Grant, Italian Medicines Agency, and the Canadian Cancer Society Research Institute.
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