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The industrial production of nylon 6 usually includes synthesizing caprolactam through the cyclohexanone-hydroxylamine route. This approach requires complex protocols, elevated temperatures, noble metal catalysts and the use of hazardous strong acids or hydroxylamine. Additionally, a significant quantity of ammonium sulphate is generated during the synthesis procedure. This study aims to develop an electrochemical reduction system for the conversion of ADN generated from the electrolytic dimerization of acrylonitrile (AN) to 6-aminocapronitrile (ACN), a precursor of nylon 6. This system utilizes a cost-effective Cu nanomaterial under eco-friendly conditions, avoiding lengthy and harsh processes, eliminating NH2OH use, and reducing low-value ammonium sulfate generation. This electrosynthesis method maintains approximately 85% ACN selectivity at 40-100 mA cm-2 when passing the charge required for 37% theoretical conversion. When extending the reaction time to achieve an 80% conversion, ACN selectivity still reached 81.6%, exceeding the theoretical value of non-selective hydrogenation by 20%. The pseudo-first-order reaction kinetic modeling proves that the reaction rate constant for ADN hydrogenation is significantly greater than that for ACN hydrogenation, highlighting the selectivity advantage of the system for ACN. This study establishes the foundation for developing a continuous electrolysis process to produce the nylon 6 precursor from AN feedstock.
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[This corrects the article DOI: 10.1039/D4SC02420F.].
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The inevitable oxidation of nickel-metal-based catalysts exposed to the air will lead to instability and poor reproducibility of a catalytic interface, which is usually ignored and greatly hinders their application for the catalysis of alkaline hydrogen oxidation. The details on the formation of a world-class nickel-based HOR catalyst Ni3-MoOx/C-500 are reported via an interfacial reconstruction triggered by passive oxidation upon air exposure. Interfacial reconstruction, initiated with various Ni-Mo metal ratios and annealing temperature, can fine-tune the Ni-Mo interface with an increased work function and a reduced d-band center. The optimized Ni3-MoOx/C exhibits a record high mass activity of 102.8 mA mgNi -1, a top-level exchange current density of 76.5 µA cmNi -2, and exceptional resistance to CO poisoning at 1000 ppm CO for hours. The catalyzed alkaline exchange membrane fuel cell exhibits a maximum power output of 600 mW cm-2 and excellent stability, ranking it as one of the most active non-precious metals HOR catalysts to date.
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Lithium-sulfur batteries (LSBs) with two typical platforms during discharge are prone to the formation of soluble lithium polysulfides (LiPS), leading to a decrease in the cycling life of the battery. Under practical working conditions, the transformation of S8 into Li2S is cross-executed rather than a stepwise reaction, where the liquid LiPS to solid Li2S conversion can occur at a high state of charge (SOC) to maintain the current requirement. Therefore, advancing Li2S deposition can effectively reduce the accumulation of LiPSs and ultimately improve the reaction kinetics. Herein, a "butterfly material" GeS2-MoS2/rGO is used as a sulfur host. Rich catalytic heterointerfaces can be obtained via the abundant S-S bonds formed between GeS2 and MoS2. MoS2 (left wing) can enhance LiPS adsorption, while the lattice-matching nature of Fdd2 GeS2 (right wing) and Fm3Ìm Li2S can induce multiple nucleation and regulate the 3D growth of Li2S. Li2S deposition can be advanced to occur at 80% SOC, thereby effectively inhibiting the accumulation of soluble LiPSs. Attributed to the synergistic effect of catalytic and lattice-matching properties, robust coin and pouch LSBs can be achieved.
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The development of non-precious hydrogen oxidation reaction (HOR) catalysts is a major challenge for the commercialization of Pt-free fuel cells. Herein, a temperature-induced phase hybridization method is reported that greatly improves the catalytic performance of NiCu alloy for the HOR. The migration of W atoms hybridizes the interface of tungsten oxide (WOx) and tungsten carbide (WC) at the onset reduction temperature of WOx, leading to a greatly weakened H binding energy and an optimized OH binding energy, which endows NiCuW/WOx-WC@WC with favorable stability and CO resistance during HOR. The hybridization catalysts deliver a high mass activity of 29.37 mA mg-1 Ni and reach a peak power of 298 mW.cm-2 in H2-O2 anion exchange membrane fuel cells (AEMFCs).
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Affordable highly efficient catalysts for electrochemical oxygen evolution reaction (OER) play pivotal roles in green hydrogen production via water electrolysis. Regarding the non-noble metal-based electrocatalysts, considerable efforts are made to decipher the cation leaching and surface reconstruction; yet, little attention is focused on correlating them with catalytical activity and stability. Herein, in situ reconstruction of Fe-modified Co2VO4 precursor catalyst to form a highly active (Fe,V)-doped CoOOH phase for OER is reported, during which partial leaching of V accelerates the surface reconstruction and the V reserved in the reconstructed CoOOH layer in the form of alkali-resistant V2O3 serves for dynamic charge compensation and prevention of excessive loss of lattice oxygen and Co dissolution. Fe substitution facilitates Co pre-oxidation and endows the catalysts with structural flexibility by elevating O 2p band level; hence, encouraging participation of lattice oxygen in OER. The optimized Co2Fe0.25V0.75O4 electrode can afford current densities of 10 and 500 mA cm-2 at low overpotentials of 205 and 320 mV, respectively, with satisfactory stability over 600 h. By coupling with Pt/C cathode, the assembled alkaline electrolyzer can deliver 500 mA cm-2 at a low cell voltage of 1.798 V, better than that of commercial RuO2 (+) || Pt/C (-).
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Aqueous zinc-ion batteries (ZIBs) are considered as a promising candidate for next-generation large-scale energy storage due to their high safety, low cost, and eco-friendliness. Unfortunately, commercialization of ZIBs is severely hindered owing to rampant dendrite growth and detrimental side reactions on the Zn anode. Herein, inspired by the metal-organic complex interphase strategy, the authors apply adenosine triphosphate (ATP) to in situ construct a multifunctional film on the metal Zn surface (marked as ATP@Zn) by a facile etching method. The ATP-induced interfacial layer enhances lipophilicity, promoting uniform Zn2+ flux and further homogenizing Zn deposition. Meanwhile, the functional interlayer improves the anticorrosion ability of the Zn anode, effectively suppressing corrosion and hydrogen evolution. Consequently, the as-prepared ATP@Zn anode in the symmetric cell exhibits eminent plating/stripping reversibility for over 2800 h at 5.0 mA cm-2 and 1 mAh cm-2. Furthermore, the assembled ATP@Zn||MnO2 full cells are investigated to evaluate practical feasibilities. This work provides an efficient and simple strategy to prepare stabilized Zn anode toward high-performance ZIBs.
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Plasma catalysis has recently been recognized as a promising route for artificial N2 reduction under mild conditions. Here we report a highly active VN catalyst for plasma-catalytic NH3 synthesis via the typical Mars-van Krevelen (MvK) mechanism. Our results indicate that NH3 synthesis occurs through the continuous regeneration and elimination of nitrogen vacancies on the VN surface. With this strategy, the VN catalyst achieves a superhigh NH3 yield of 143.2 mg h-1 gcat.-1 and a competitive energy efficiency of 1.43 gNH3 kW h-1.
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Ruthenium dioxide is presently the most active catalyst for the oxygen evolution reaction (OER) in acidic media but suffers from severe Ru dissolution resulting from the high covalency of Ru-O bonds triggering lattice oxygen oxidation. Here, we report an interstitial silicon-doping strategy to stabilize the highly active Ru sites of RuO2 while suppressing lattice oxygen oxidation. The representative Si-RuO2-0.1 catalyst exhibits high activity and stability in acid with a negligible degradation rate of ~52 µV h-1 in an 800 h test and an overpotential of 226 mV at 10 mA cm-2. Differential electrochemical mass spectrometry (DEMS) results demonstrate that the lattice oxygen oxidation pathway of the Si-RuO2-0.1 was suppressed by â¼95% compared to that of commercial RuO2, which is highly responsible for the extraordinary stability. This work supplied a unique mentality to guide future developments on Ru-based oxide catalysts' stability in an acidic environment.
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High-performance proton exchange membrane (PEM) is crucial for the proton exchange membrane fuel cell (PEMFC). Herein, a novel "self-enhanced" PEM is fabricated for the first time, which is composed of perfluorinated sulfonic acid (PFSA) resin and its own nanofibers as reinforcement. With this strategy, the interfacial compatibility issue of conventional fiber-reinforced membranes is fully addressed and up to 80 wt% loading of PFSA nanofibers can be incorporated. Furthermore, on account of chain orientation within the PFSA nanofiber, single fiber exhibits super-high conductivity of 1.45 S cm-1, leading to state-of-the-art proton conductivity (1.1 S cm-1) of the as-prepared "self-enhanced" PEM so far, which is an order of magnitude increase compared with the bulk PFSA membrane (0.29 S cm-1). It surpasses any commercial PEM including the popular GORE-SELECT and Nafion HP membranes and is the only PEM with conductivity at 100 S cm-1 level. In addition, the mechanical strength and swelling ratio of membranes are both substantially improved simultaneously. Based on the high-performance "self-enhanced" PEM, high peak power densities of up to 3.6 W cm-2 and 1.7 W cm-2 are achieved in H2-O2 and H2-Air fuel cells, respectively. This strategy can be applied in any polymeric electrolyte membrane.
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Fe-N-C catalysts are promising alternatives to Pt-based electrocatalysts for the oxygen reduction reaction (ORR) in various electrochemical applications. However, their practical implementation is impeded by their instability during prolonged operation. Various degradation mechanisms have been proposed, yet the real origin of the intrinsic instability of Fe-N-C structures under ORR operations is still disputed. Herein, we observed a new type of protonation mechanism based on advanced first-principles simulations and experimental characterizations. The results revealed strong evidence of pyrrolic-N protonation in pyrrolic-type FeN4, which plays a vital role for the low kinetic barrier of Fe leaching. Conversely, the pyridinic-type FeN4 prefers protonation at the Fe site, contributing to the higher barrier of Fe leaching and relatively higher stability. The facile pyrrolic-N protonation is verified by various spectroscopy characterizations in the Nafion-treated FePc molecule. Crucially, the presence of oxygen-containing intermediates at the Fe site can further work synergistically with N protonation to promote conversion of iron atoms (Fe-N4) into ferric oxide under working potentials, and the more positive the electrode potential, the lower the kinetic barrier of Fe leaching. These findings serve as a foundation for future research endeavors on the stability issues of Fe-N-C catalysts and advancing their application in sustainable energy conversion technologies.
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Substituting the low-value oxygen evolution reaction (OER) with thermodynamically more favored organic oxidation such as furfural oxidation reaction (FOR) is regarded as a perspective approach to decrease energy cost of hydrogen evolution from water splitting. However, the kinetic of FOR can be even more sluggish than OER under large current density. In this work, a strategy is proposed to accelerate FOR by enhancing the adsorption of oxygenates on active sites. Over the prepared NiMoP/NF anode, only 1.46 V versus RHE is required in furfural solution to achieve 500 mA cm-2 , significantly better than the OER activity over commercial RuO2 /NF under the same current density (1.57 V vs RHE).
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Correction for 'Strengthening Pt/WOx interfacial interactions to increase the CO tolerance of Pt for hydrogen oxidation reaction' by Daojun Long et al., Chem. Commun., 2023, https://doi.org/10.1039/d3cc03990k.
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Addressing phosphoric acid poisoning of platinum-based catalysts in high-temperature fuel cells still remains a strategic and synthetic problem. Here, we synthesized a Pt3Co@MoOx-NC catalyst with a Pt3Co active core and MoOx modification on the surface, which simultaneously exhibits high ORR activity and phosphate tolerance.
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Here, the modulation of the Pt electronic structure by the formation of an amorphous WOx overlayer on Pt nanoparticles is proposed. The resulting Pt/WOx@NC electrode shows exceptional CO oxidation potential (0.24 V vs. RHE) in aqueous test, and the corresponding membrane electrode assembly (MEA) steadily generates power in fuel cells fed with H2 gas containing 1000 ppm CO.
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Accurate identification of active sites is highly desirable for elucidation of the reaction mechanism and development of efficient catalysts. Despite the promising catalytic performance of thiolated metal nanoclusters (NCs), their actual catalytic sites remain elusive. Traditional first-principles calculations and experimental observations suggested dealkylated S and dethiolated metal, respectively, to be the active centers. However, the real kinetic origin of thiolate etching during the electrocatalysis of NCs is still puzzling. Herein, we conducted advanced first-principles calculations and electrochemical/spectroscopic experiments to unravel the electrochemical etching kinetics of thiolate ligands in prototype Au25(SCH3)18 NC. The electrochemical processes are revealed to be spontaneously facilitated by dethiolation (i.e., desorption of -SCH3), forming the free HSCH3 molecule after explicitly including the solvent effect and electrode potential. Thus, exposed under-coordinated Au atoms, rather than the S atoms, serve as the real catalytic sites. The thermodynamically preferred Au-S bond cleavage arises from the selective attack of H from proton/H2O on the S atom under suitable electrochemical bias due to the spatial accessibility and the presence of S lone pair electrons. Decrease of reduction potential promotes the proton attack on S and significantly accelerates the kinetics of Au-S bond breakage irrespective of the pH of the medium. Our theoretical results are further verified by the experimental electrochemical and spectroscopic data. At more negative electrode potentials, the number of -SR ligands decreased with concomitant increase of the vibrational intensity of S-H bonds. These findings together clarify the atomic-level activation mechanism on the surface of Au25(SR)18 NCs.
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Stoichiometric oxidants are always consumed in organic oxidation reactions. For example, olefins react with peroxy acids to be converted to epoxy, while the oxidant, peroxy acid, is downgraded to carboxylic acid. In this paper, we aim to regenerate carboxylic acid into peroxy acid through electric water splitting at the anode, in order to construct an electrochemical catalytic cycle to accomplish the cycloolefin epoxidation reaction. Benzoic acid, which can be strongly adsorbed onto the anode and rapidly converted to peroxy acid, was selected to catalyze the cycloolefin epoxidation. Furthermore, the peroxybenzoic acid will be further activated on the electrode to fulfill the epoxidation and release the benzoic acid to complete the catalytic cycle. In this designed reaction cycle, benzoic acid acts as a molecular catalyst with the assistance of the electrode-generated reactive oxygen species (ROS). This method can successfully reform the consumable oxidants to molecular catalysts, which can be generalized to other green organic syntheses.
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PURPOSE: This study intended to compare the difference between the anterior talofibular ligament (ATFL) and posterior talofibular ligament (PTFL) angle with chronic ankle instability (CAI) patients and healthy volunteers, and to confirm whether using the ATFL-PTFL angle could be a reliable assessment method for CAI, so as to improve the accuracy and specificity of clinical diagnosis. METHODS: This retrospective study included 240 participants: 120 CAI patients and 120 healthy volunteers between 2015 and 2021. The ATFL-PTFL angle of the ankle region was gaged in the cross-sectional supine position on MRI between two groups. After participants undergoing a comprehensive MRI scanning, ATFL-PTFL angles were regarded as the main indicator of patients with the injured ATFLs and healthy volunteers to compare, and were measured by an experienced musculoskeletal radiologist. Moreover, other qualitative and quantitative indicators referring to anatomical and morphological characteristics of the AFTL were included in this study with MRI, such as the length, width, thickness, shape, continuity, and signal intensity of the ATFL, which can be used as secondary indicators. RESULTS: In the CAI group, the ATFL-PTFL angle was 90.8° ± 5.7°, which was significantly different from the non-CAI group where the ATFL-PTFL angle for 80.0° ± 3.7° (p < 0.001). As for the ATFL-MRI characteristics, the length (p = 0.003), width (p < 0.001), and thickness (p < 0.001) in the CAI group were also significantly different from the non-CAI group. Over 90% of the cases, patients of the CAI group had injured ATFL with an irregular shape, non-continuous, and high or mixed signal intensity. CONCLUSION: Compared with healthy people, the ATFL-PTFL angle of most CAI patients is larger, which can be used as a secondary index to diagnose CAI. However, the MRI characteristic changes of ATFL may not relate to the increased ATFL-PTFL angle.
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Inestabilidad de la Articulación , Ligamentos Laterales del Tobillo , Humanos , Ligamentos Laterales del Tobillo/diagnóstico por imagen , Articulación del Tobillo/diagnóstico por imagen , Articulación del Tobillo/anatomía & histología , Estudios Retrospectivos , Tobillo , Estudios Transversales , Imagen por Resonancia Magnética/métodos , Inestabilidad de la Articulación/diagnóstico por imagenRESUMEN
The charge process of lithium-sulfur batteries (LSBs) is a process in which molecular polarity decreases and the volume shrinks gradually, which is the process most likely to cause lithium polysulfides (LiPSs) loss and interfacial collapse. In this work, GeS2 is utilized, whose (111) lattice plane exactly matches with the (113) lattice of α-S8 , to solve these problems. GeS2 can regulate the interconversion-deposition behavior of S-species during the charge process. Soluble LiPSs can be spontaneously adsorbed on the GeS2 surface, then obtain electrons and eventually convert to α-S8 molecules. More importantly, the α-S8 molecules will crystallize uniformly along the (111) lattice plane of GeS2 to maintain a stable cathode-electrolyte interface. Therefore, outstanding charge/discharge LSBs are successfully accomplished.
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Structurally optimized transition metal phosphides are identified as a promising avenue for the commercialization of lithium-sulfur (Li-S) batteries. In this study, a CoP nanoparticle-doped hollow ordered mesoporous carbon sphere (CoP-OMCS) is developed as a S host with a "Confinement-Adsorption-Catalysis" triple effect for Li-S batteries. The Li-S batteries with CoP-OMCS/S cathode demonstrate excellent performance, delivering a discharge capacity of 1148 mAh g-1 at 0.5 C and good cycling stability with a low long-cycle capacity decay rate of 0.059% per cycle. Even at a high current density of 2 C after 200 cycles, a high specific discharge capacity of 524 mAh g-1 is maintained. Moreover, a reversible areal capacity of 6.56 mAh cm-2 is achieved after 100 cycles at 0.2 C, despite a high S loading of 6.8 mg cm-2 . Density functional theory (DFT) calculations show that CoP exhibits enhanced adsorption capacity for sulfur-containing substances. Additionally, the optimized electronic structure of CoP significantly reduces the energy barrier during the conversion of Li2 S4 (L) to Li2 S2 (S). In summary, this work provides a promising approach to optimize transition metal phosphide materials structurally and design cathodes for Li-S batteries.