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As a promising environmental remediation technology, the electro-Fenton (EF) process is mainly limited by the two rate-limiting steps, which are H2O2 generation and activation. The electrocatalytic three-electron oxygen reduction reaction (3e- ORR) can directly activate oxygen to hydroxyl radicals (â¢OH), which is expected to break through the rate-limiting steps of the EF process. However, limited success has been achieved in the design of 3e- ORR electrocatalysts. Herein, we propose Cu/CoSe2/C with the strong metal-support interactions to enhance the 3e- ORR process, exhibiting remarkable reactivity and stability for â¢OH generation. Both experiment and DFT calculation results reveal that CoSe2 is conducive to the generation of H2O2. Meanwhile, the metallic Cu can enhance the adsorption strength of *H2O2 intermediates and thus promotes the one-electron reduction to â¢OH. The Cu/CoSe2/C catalyst exhibits the electron-transfer number close to 3.0 during the ORR process, and exhibits the outstanding â¢OH generation performance, achieving a higher apparent rate constant (6.0 times faster) toward ciprofloxacin compared with its analogy without the SMSI effect. Our work represents that the SMSI effect endows Cu/CoSe2/C high activity and selectivity for â¢OH generation, providing a unique perspective for the design of a high-efficiency 3e- ORR catalyst.
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Understanding the evolutionary factors that impact the genetic architecture of traits is a central goal of evolutionary genetics. Here, we investigate how quantitative trait variation accumulated over time in populations that colonized a novel environment. We compare the genetic architecture of flowering time in Arabidopsis populations from the drought-prone Cape Verde Islands and their closest outgroup population from North Africa. We find that trait polygenicity is severely reduced in the island populations compared to the continental North African population. Further, trait architectures and reconstructed allelic histories best fit a model of strong directional selection in the islands in accord with a Fisher-Orr adaptive walk. Consistent with this, we find that large-effect variants that disrupt major flowering time genes (FRI and FLC) arose first, followed by smaller effect variants, including ATX2 L125F, which is associated with a 4-day reduction in flowering time. The most recently arising flowering time-associated loci are not known to be directly involved in flowering time, consistent with an omnigenic signature developing as the population approaches its trait optimum. Surprisingly, we find no effect in the natural population of EDI-Cvi-0 (CRY2 V367M), an allele for which an effect was previously validated by introgression into a Eurasian line. Instead, our results suggest the previously observed effect of the EDI-Cvi-0 allele on flowering time likely depends on genetic background, due to an epistatic interaction. Altogether, our results provide an empirical example of the effects demographic history and selection has on trait architecture.
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Proteínas de Arabidopsis , Arabidopsis , África do Norte , Alelos , Arabidopsis/genética , Evolução Biológica , Demografia , Proteínas de Arabidopsis/genéticaRESUMO
The development of economical and efficient oxygen reduction reaction (ORR) catalysts is crucial to accelerate the widespread application rhythm of aqueous rechargeable zinc-air batteries (ZABs). Here, a strategy is reported that the modification of the binding energy for reaction intermediates by the axial N-group converts the inactive spinel MgAl2O4 into the active motif of MgAl2O4-N. It is found that the introduction of N species can effectively optimize the electronic configuration of MgAl2O4, thereby significantly reducing the adsorption strength of *OH and boosting the reaction process. This main-group MgAl2O4-N catalyst exhibits a high ORR activity in a broad pH range from acidic and alkaline environments. The aqueous ZABs assembled with MgAl2O4-N shows a peak power density of 158.5 mW cm-2, the long-term cyclability over 2000 h and the high stability in the temperature range from -10 to 50 °C, outperforming the commercial Pt/C in terms of activity and stability. This work not only serves as a significant candidate for the robust ORR electrocatalysts of aqueous ZABs, but also paves a new route for the effective reutilization of waste Mg alloys.
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Perovskite oxides exhibit bifunctional activity for both oxygen reduction (ORR) and oxygen evolution reactions (OER), making them prime candidates for energy conversion in applications like fuel cells and metal-air batteries. Their intrinsic catalytic prowess, combined with low-cost, abundance, and diversity, positions them as compelling alternatives to noble metal and metal oxides catalysts. This review encapsulates the nuances of perovskite oxide structures and synthesis techniques, providing insight into pivotal active sites that underscore their bifunctional behavior. The focus centers on the breakthroughs surrounding lanthanum (La) and strontium (Sr)-based perovskite oxides, specifically their roles in zinc-air batteries (ZABs). An introduction to the mechanisms of ORR and OER is provided. Moreover, the light is shed on strategies and determinants central to optimizing the bifunctional performance of La and Sr-based perovskite oxides.
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Noble metal-based catalyst, despite their exorbitant cost, are the only successful catalyst for bifunctional oxygen electrocatalysis owing to their capability to drive forward the reaction rate kinetically. Therefore, it is desirable to diminish the noble metal loading without any compromise in the catalyst performance. In this study, the aim to achieve two goals with one action via a single-step route to have ultra-low loading of Pd in the catalyst. The Pd is used as a catalyst for CâC bond formation followed by complexation reactions or vice versa, in conventional Suzuki-Miyaura cross-coupling (SMCC) reaction, which yields a Pd-based porous organic polymer. Interestingly, it is found that dispersed Pd nanocluster (PdNC ) is present together with Pd single atom doped into nanocarbon (Pd-NC) matrix in the catalyst (PdNC /Pd-NC800 ) that obtained after pyrolysis of the porous polymer. The catalyst exhibits remarkable bifunctional activity and durability towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Further, it is studied that the in situ attenuated total reflection infrared (ATR-IR) spectroscopy at different electrochemical potentials during ORR and OER to observe the reaction intermediates. The homemade zinc-air battery with the catalyst displayed great performance, establishing the significance of PdNC /Pd-NC800 as a bifunctional oxygen electrocatalyst.
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The synthesis of stable polynitrogen compounds with high-energy density has long been a major challenge. The cyclo-pentazolate anion (cyclo-N5 -) is successfully converted into aromatic and structurally symmetric bipentazole (N10) via electrochemical synthesis using highly conductive multi-walled carbon nanotubes (MWCNTs) as the substrate and sodium pentazolate hydrate ([Na(H2O)(N5)]·2H2O) as the raw material. Attenuated total refraction Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and density functional theory calculations confirmed the structure and homogeneous distribution of N10 in the sidewalls of the MWCNTs (named MWCNT-N10-n m). The MWCNT-N10-2.0 m is further used as a catalyst for electrochemical oxygen reduction to synthesize hydrogen peroxide from oxygen with a two-electron selectivity of up to 95%.
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Driven by the pressing demand for stable energy systems, zinc-air batteries (ZABs) have emerged as crucial energy storage solutions. However, the quest for cost-effective catalysts to enhance vital oxygen evolution and reduction reactions remains challenging. FeNiCo|MnGaOx heterostructure nanoparticles on carbon nanotubes (CNTs) are synthesized using liquid-phase reduction and H2 calcination approach. Compared to its component, such FeNiCo|MnGaOx/CNT shows a high synergistic effect, low impedance, and modulated electronic structure, leading to a superior bifunctional catalytic performance with an overpotential of 255 mV at 10 mA cm-2 and half-wave potential of 0.824 V (ω = 1600 rpm and 0.1 m KOH electrolyte). Moreover, ZABs based on FeNiCo|MnGaOx/CNT demonstrate notable features, including a peak power density of 136.1 mW cm-2, a high specific capacity of 808.3 mAh gZn -1, and outstanding stability throughout >158 h of uninterrupted charge-discharge cycling. Theoretical calculations reveal that the non-homogeneous interface can introduce more carriers and altered electronic structures to refine intermediate adsorption reactions, especially promoting O* formation, thereby enhancing electrocatalytic performance. This work demonstrates the importance of heterostructure interfacial modulation of electronic structure and enhancement of adsorption capacity in promoting the implementation of OER/ORR, ZABs, and related applications.
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The high energy demand of the evolving world opens the door to develop more sustainable and environmentally friendly energy sources. Oxygen reduction reaction (ORR) is a promising candidate, being the 2e- pathway of great interest for the green production of hydrogen peroxide. Metal-free covalent organic frameworks (COFs) electrocatalysts present a suitable alternative to substitute the noble-metals more commonly employed in this application. However, the lability of the linkages building up the framework raises an issue for their long-term use and application in aggressive media. Herein, a stable amide-linked COF is reported through post-synthetic modification of a previously reported imine-linked COF proven to be effective as an electrocatalyst, enhancing its chemical stability and electrochemical response. It is found that after the linkage transformation, the new electrocatalyst displays a higher selectivity toward the H2O2 production (98.5%) and an enhanced turnover frequency of 0.155 s-1, which is among the bests reported to date for metal-free and COF based electrocatalysts. The results represent a promising step forward for metal-free non pyrolyzed electrocatalysts, improving their properties through post-synthetic linkage modification for long-term operation.
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In this work, Pt3Fe nanoparticles (Pt3Fe NPs) with the ordered internal structure and Pt-rich shells surrounded by plenty of Fe single atoms (Fe SAs) as active species (Pt3Fe NP-in-Fe SA) loaded in the carbon materials are successfully fabricated, which are abbreviated as island-in-sea structured (IISS) Pt3Fe NP-in-Fe SA catalysts. Moreover, the synergistic effect of O-bridging between Pt3Fe NPs and Fe SAs, and the ordered internal structured Pt3Fe NPs with Pt-rich shells of an optimal thickness contributes to the achievement of the local acidic environments on the surfaces of Pt3Fe NPs in the alkaline hydrogen evolution reaction (HER) and the enhancement of the desorption rate of *OH intermediate in the acidic oxygen reduction reaction (ORR). In addition, the electronic interactions between Pt3Fe NPs and dispersed Fe SAs cannot only provide efficient electrons transfer, but also prevent the aggregation and dissolution of Pt3Fe NPs. Furthermore, the overpotential and the half wave potential of the as-prepared IISS Pt3Fe NP-in-Fe SA catalysts toward the alkaline HER and toward the acidic ORR are 8 mV at a current density of 10 mA cm-2 and 0.933 V, respectively, which is 29 lower and 86 mV higher than those (37 mV and 0.847 V) of commercial Pt/C catalysts.
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Carbon materials hold significant promise in electrocatalysis, particularly in electrochemical CO2 reduction reaction (eCO2 RR) and two-electron oxygen reduction reaction (2e- ORR). The pivotal factor in achieving exceptional overall catalytic performance in carbon catalysts is the strategic design of specific active sites and nanostructures. This work presents a comprehensive overview of recent developments in carbon electrocatalysts for eCO2 RR and 2e- ORR. The creation of active sites through single/dual heteroatom doping, functional group decoration, topological defect, and micro-nano structuring, along with their synergistic effects, is thoroughly examined. Elaboration on the catalytic mechanisms and structure-activity relationships of these active sites is provided. In addition to directly serving as electrocatalysts, this review explores the role of carbon matrix as a support in finely adjusting the reactivity of single-atom molecular catalysts. Finally, the work addresses the challenges and prospects associated with designing and fabricating carbon electrocatalysts, providing valuable insights into the future trajectory of this dynamic field.
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Decorating platinum (Pt) with a single atom offers a promising approach to tailoring their catalytic activity. In this study, for the first time, an innovative assistive active sites (AAS) strategy is proposed to construct high-loading (3.46wt.%) single FeâN4 as AAS, which are further hybridized with small Pt nanoparticles to enhance both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activities. For ORR, the target catalyst (Pt/HFeSA-HCS) exhibits a higher mass activity (MA) of 0.98 A mgPt -1 and specific activity (SA) of 1.39 mA cmPt -2 at 0.90 V versus RHE. As for MOR, Pt/HFeSA-HCS shows exceptional MA (3.21 A mgPt -1) and SA (4.27 mA cmPt -2) at peak values, surpassing commercial Pt/C by 15.3 and 11.5 times, respectively. The underlying mechanism behind this AAS strategy is to find that in MOR, FeâN4 promotes water dissociation, generating more *OH to accelerate the conversion of *CO to CO2. Meanwhile, in ORR, FeâN4 acts as a competitor to adsorb *OH, weakening PtâOH bonding and facilitating desorption of *OH on the Pt surface. Constructing AAS that can enhance dual functionality simultaneously can be seen as a successful "kill two birds with one stone" strategy.
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Ammonia fuel cells using carbon-neutral ammonia as fuel are regarded as a fast, furious, and flexible next-generation carbon-free energy conversion technology, but it is limited by the kinetically sluggish ammonia oxidation reaction (AOR), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). Platinum can efficiently drive these three types of reactions, but its scale-up application is limited by its susceptibility to poisoning and high cost. In order to reduce the cost and alleviate poisoning, incorporating Pt with various metals proves to be an efficient and feasible strategy. Herein, PtFeCoNiIr/C trifunctional high-entropy alloy (HEA) catalysts are prepared with uniform mixing and ultra-small size of 2 ± 0.5 nm by Joule heating method. PtFeCoNiIr/C exhibits efficient performance in AOR (Jpeak = 139.8 A g-1 PGM), ORR (E1/2 = 0.87 V), and HER (E10 = 20.3 mV), outperforming the benchmark Pt/C, and no loss in HER performance at 100 mA cm-2 for 200 h. The almost unchanged E1/2 in the anti-poisoning test indicates its promising application in real fuel cells powered by ammonia. This work opens up a new path for the development of multi-functional electrocatalysts and also makes a big leap toward the exploration of cost-effective device configurations for novel fuel cells.
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Graphene supported electrocatalysts have demonstrated remarkable catalytic performance for oxygen reduction reaction (ORR). However, their durability and cycling performance are greatly limited by Oswald ripening of platinum (Pt) and graphene support corrosion. Moreover, comprehensive studies on the mechanisms of catalysts degradation under 0.6-1.6 V versus RHE (Reversible Hydrogen Electrode) is still lacking. Herein, degradation mechanisms triggered by different defects on graphene supports are investigated by two cycling protocols. In the start-up/shutdown cycling (1.0-1.6 V vs. RHE), carbon oxidation reaction (COR) leads to shedding or swarm-like aggregation of Pt nanoparticles (NPs). Theoretical simulation results show that the expansion of vacancy defects promotes reaction kinetics of the decisive step in COR, reducing its reaction overpotential. While under the load cycling (0.6-1.0 V vs. RHE), oxygen containing defects lead to an elevated content of Pt in its oxidation state which intensifies Oswald ripening of Pt. The presence of vacancy defects can enhance the transfer of electrons from graphene to the Pt surface, reducing the d-band center of Pt and making it more difficult for the oxidation state of platinum to form in the cycling. This work will provide comprehensive understanding on Pt/Graphene catalysts degradation mechanisms.
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The key to design an advanced oxygen reduction reaction (ORR) electrocatalyst is a well-balance between the adsorption and desorption of oxygen intermediates. This study systematically evaluated the ORR activity of HCP and FCC cobalt core-shell cobalt/N-doped carbon (Cobalt@NC) catalyst via theoretical and experimental studies. The electronic structure calculations using density functional theory (DFT) calculations revealed that the ORR activity of carbon layer can be improved by 1) switching the electrostatic potential in the electrical double layer due to the polarization induced at the carbon-cobalt interface and 2) modulating the electron population in the bonding orbital in the C-O bonds in an ORR. The results revealed that an O atom is bounded stronger to the outer NC shell with FCC Cobalt than HCP Cobalt, which hindered the desorption steps of OH*. Experimentally, plasma-engineered HCP Cobalt@NC also showed remarkably advanced performance toward ORR compared to that FCC Cobalt@NC. The kinetic current density of HCP Cobalt@NC at 0.85 V versus RHE is calculated as 6.24 mA cm-2, which is six folds higher than FCC Cobalt@NC and even outperform 20 wt.% Pt/C. In a practical Aluminium-air battery, HCP Cobalt@NC also exhibited slightly higher peak power density (110.57 mW cm-2) compared to 20 wt.% Pt/C.
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Photocatalytic H2O2 production is a green and sustainable route, but far from meeting the increasing demands of industrialization due to the rapid recombination of the photogenerated charge carriers and the sluggish reaction kinetics. Effective strategies for precisely regulating the photogenerated carrier behavior and catalytic activity to construct high-performance photocatalysts are urgently needed. Herein, a nitrogen-site engineering strategy, implying elaborately tuning the species and densities of nitrogen atoms, is applied for H2O2 photogeneration performance regulation. Different nitrogen heterocycles, such as pyridine, pyrimidine, and triazine units, are polymerized with trithiophene units, and five covalent organic frameworks (COFs) with distinct nitrogen species and densities on the skeletons are obtained. Fascinatingly, they photocatalyzed H2O2 production via dominated two-electron O2 reduction processes, including O2-O2 â¢â-H2O2 and O2-O2 â¢â-O2 1-H2O2 dual pathways. Just in the air and pure water, the multicomponent TTA-TF-COF with the maximum nitrogen densities triazine nitrogen densities exhibited the highest H2O2 production rate of 3343 µmol g-1 h-1, higher than most of other reported COFs. The theoretical calculation revealed the higher activity is due to the easy formation of O2 â¢â and O2 1 in different catalytic process. This study gives a new insight into designing photocatalysis at atomic level.
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X-ray spectroscopy is a valuable technique for the study of many materials systems. Characterizing reactions in situ and operando can reveal complex reaction kinetics, which is crucial to understanding active site composition and reaction mechanisms. In this project, the design, fabrication and testing of an open-source and easy-to-fabricate electrochemical cell for in situ electrochemistry compatible with X-ray absorption spectroscopy in both transmission and fluorescence modes are accomplished via windows with large opening angles on both the upstream and downstream sides of the cell. Using a hobbyist computer numerical control machine and free 3D CAD software, anyone can make a reliable electrochemical cell using this design. Onion-like carbon nanoparticles, with a 1:3 iron-to-cobalt ratio, were drop-coated onto carbon paper for testing in situ X-ray absorption spectroscopy. Cyclic voltammetry of the carbon paper showed the expected behavior, with no increased ohmic drop, even in sandwiched cells. Chronoamperometry was used to apply 0.4â V versus reversible hydrogen electrode, with and without 15â min of oxygen purging to ensure that the electrochemical cell does not provide any artefacts due to gas purging. The XANES and EXAFS spectra showed no differences with and without oxygen, as expected at 0.4â V, without any artefacts due to gas purging. The development of this open-source electrochemical cell design allows for improved collection of in situ X-ray absorption spectroscopy data and enables researchers to perform both transmission and fluorescence simultaneously. It additionally addresses key practical considerations including gas purging, reduced ionic resistance and leak prevention.
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The extracellular matrix (ECM) is a dynamic and complex microenvironment that modulates cell behavior and cell fate. Changes in ECM composition and architecture have been correlated with development, differentiation, and disease progression in various pathologies, including breast cancer [1]. Studies have shown that aligned fibers drive a pro-metastatic microenvironment, promoting the transformation of mammary epithelial cells into invasive ductal carcinoma via the epithelial-to-mesenchymal transition (EMT) [2]. The impact of ECM orientation on breast cancer metabolism, however, is largely unknown. Here, we employ two non-invasive imaging techniques, fluorescence-lifetime imaging microscopy (FLIM) and intensity-based multiphoton microscopy, to assess the metabolic states of cancer cells cultured on ECM-mimicking nanofibers in a random and aligned orientation. By tracking the changes in the intrinsic fluorescence of nicotinamide adenine dinucleotide and flavin adenine dinucleotide, as well as expression levels of metastatic markers, we reveal how ECM fiber orientation alters cancer metabolism and EMT progression. Our study indicates that aligned cellular microenvironments play a key role in promoting metastatic phenotypes of breast cancer as evidenced by a more glycolytic metabolic signature on nanofiber scaffolds of aligned orientation compared to scaffolds of random orientation. This finding is particularly relevant for subsets of breast cancer marked by high levels of collagen remodeling (e.g. pregnancy associated breast cancer), and may serve as a platform for predicting clinical outcomes within these subsets [3-6].
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The production of metal-organic framework (MOF) nanoplates with well-defined geometric morphology is remarkable for expanding their applications. Herein, the cobalt-based MOF nanoplates with hexagonal channels from a layer-pillared MOF are accomplished, via a molecular scalpel strategy, utilizing monodentate pyridine to replace the bidentate 4,4'-bipyridine. The morphology can be modified from nanorods to nanoplates with controllable thickness tuned by the amounts of pyridine. Succeeding carbonization treatment transforms the MOF nanoplates into Co particles homogeneously encapsulated in the nitrogen-doped carbon layers. The prepared catalyst with a unique platelike morphology displays a high half-wave potential of 0.88â V in oxygen reduction reaction. When used in primary Zn-air batteries, it delivers a high peak power density of 280â mW cm-2 . This work clarifies the structure-morphology-reactivity connection of MOF nanoplates.
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We systematically investigated the stable configurations and catalytic activity in the Oxygen Reduction Reaction (ORR) of graphene co-doped with boron and nitrogen (B-N) using first-principles methods. Compared to single B/N doping, co-doping with BN is energetically favored. We found that intermediate species of ORR process adsorb on boron atoms, which act as catalytic sites. The presence of neighboring nitrogen atoms around boron plays a crucial role in modulating the catalytic activity of boron. For the same adsorption configuration, the adsorption energy of the adsorbate increases with the number of neighboring nitrogen atoms around boron and generally correlates positively with the number of electrons gained by the adsorbate. Regarding the catalytic activity of ORR, excessively strong adsorption of adsorbates impedes their hydrogenation. The best substrates for ORR catalytic activity are B-N-graphene and N-B2-graphene, with the rate-determining step being the hydrogenation of *OO and overpotentials of 0.49â V and 0.54â V, respectively.
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In recent years, the rapid growth in renewable energy applications has created a significant demand for efficient energy storage solutions on a large scale. Among the various options, rechargeable zinc-air batteries (ZABs) have emerged as an appealing choice in green energy storage technology due to their higher energy density, sustainability, and cost-effectiveness. Regarding this fact, a spotlight is shaded on air electrode for constructing high-performance ZABs. Cobalt oxide-based electrocatalysts on the air electrode have gained significant attention due to their extraordinary features. Particularly, exploration and integration of bifunctional behavior for energy storage has remarkably promoted both ORR and OER to facilitate the overall performance of the battery. The plot of this review is forwarded towards in-depth analysis of the latest advancements in electrocatalysts that are based on cobalt oxide and possess bifunctional properties along with an introduction of the fundamental aspects of ZABs, Additionally, the topic entails an examination of the morphological variations and mechanistic details mentioning about the synthesis processes. Finally, a direction is provided for future research endeavors through addressing the challenges and prospects in the advancement of next-generation bifunctional electrocatalysts to empower high-performing ZABs with bifunctional cobalt oxide.