What Elements Really Intercalate into Pd Lattice When Heated in Dimethylformamide?

Palladium hydrides (PdHx) are pivotal in both fundamental research and practical applications across a wide spectrum. PdHx nanocrystals, synthesized by heating in dimethylformamide (DMF), exhibit remarkable stability, granting them widespread applications in the field of electrocatalysis. However, this stability appears inconsistent with their metastable nature. The substantial challenges in characterizing nanoscale structures contribute to the limited understanding of this anomalous phenomenon. Here, through a series of well-conceived experimental designs and advanced characterization techniques, including aberration-corrected scanning transmission electron microscopy (AC-STEM), in situ X-ray diffraction (XRD), and time-of-flight secondary ion mass spectrometry (TOF-SIMS), we have uncovered evidence that indicates the presence of C and N within the lattice of Pd (PdCxNy), rather than H (PdHx). By combining theoretical calculations, we have thoroughly studied the potential configurations and thermodynamic stability of PdCxNy, demonstrating a 2.5:1 ratio of C to N infiltration into the Pd lattice. Furthermore, we successfully modulated the electronic structure of Pd nanocrystals through C and N doping, enhancing their catalytic activity in methanol oxidation reactions. This breakthrough provides a new perspective on the structure and composition of Pd-based nanocrystals infused with light elements, paving the way for the development of advanced catalytic materials in the future.

Improving the Hydrogen Oxidation Reaction Rate of Ru by Active Hydrogen in the Ultrathin Pd Interlayer.

Enhancing the catalytic activity of Ru metal in the hydrogen oxidation reaction (HOR) potential range, improving the insufficient activity of Ru caused by its oxophilicity, is of great significance for reducing the cost of anion exchange membrane fuel cells (AEMFCs). Here, we use Ru grown on Au@Pd as a model system to understand the underlying mechanism for activity improvement by combining direct in situ surface-enhanced Raman spectroscopy (SERS) evidence of the catalytic reaction intermediate (OHad) with in situ X-ray diffraction (XRD), electrochemical characterization, as well as DFT calculations. The results showed that the Au@Pd@Ru nanocatalyst utilizes the hydrogen storage capacity of the Pd interlayer to "temporarily" store the activated hydrogen enriched at the interface, which spontaneously overflows at the "hydrogen-deficient interface" to react with OHad adsorbed on Ru. It is the essential reason for the enhanced catalytic activity of Ru at anodic potential. This work deepens our understanding of the HOR mechanism and provides new ideas for the rational design of advanced electrocatalysts.

Accelerated Water Oxidation Kinetics Triggered by Supramolecular Porphyrin Nanosheet for Robust Visible-Light-Driven CO2 Reduction.

Water oxidation is one of the most challenging steps in CO2 photoreduction, but its influence on CO2 photoreduction is still poorly understood. Herein, the concept of accelerating the water oxidation kinetics to promote the CO2 photoreduction is realized by incorporating supramolecular porphyrin nanosheets (NS) into the C3 N4 catalyst. As a prototype, porphyrin-C3 N4 based van der Waals heterojunctions with efficient charge separation are elaborately designed, in which the porphyrin and C3 N4 NS serve as the water oxidation booster and CO2 reduction center, respectively. Theoretical calculations and relevant experiments demonstrate that the added porphyrin NS reverses the rate-limiting step in the water oxidation while reducing its energy barrier, thus resulting in faster reaction kinetics. Therefore, the optimal sample shows excellent performance in visible-light-driven CO2 reduction with a maximum CO evolution rate of 16.8 µmol g-1 h-1 , which is 6.8 times that of the C3 N4 NS and reaches the current state of the art for C3 N4 -based materials in CO2 photoreduction. Overall, this work throws light that accelerating water oxidation kinetics can effectively improve the CO2 photoreduction efficiency.

Platinum-Tin/Tin Oxide/CNT Catalysts for High-Performance Electrocatalytic Ethanol Oxidation.

Ethanol is a promising liquid clean energy source in the energy conversion field. However, the self-poisoning caused by the strongly adsorbed reaction intermediates (typically, CO) is a critical problem in ethanol oxidation reaction. To address this issue, we proposed a joint use of two strategies, alloying of Pt with other metals and building Pt/metal-oxide interfaces, to achieve high-performance electrocatalytic ethanol oxidation. For this, a well-designed synthetic route combining wet impregnation with a two-step thermal treatment process was established to construct PtSn/SnOx interfaces on carbon nanotubes. Using this route, the alloying of Pt-Sn and formation of PtSn-SnOx interfaces can simultaneously be achieved, and the coverage of SnOx thin films on PtSn alloy nanoparticles can be facilely tuned by the strong interaction between Pt and SnOx . The results revealed that the partial coverage of SnOx species not only retained the active sites, but also enhanced the CO anti-poisoning ability of the catalyst. Consequently, the H-PtSn/SnOx /CNT-2 catalyst with an optimized PtSn-SnOx interface showed significantly improved performances toward the ethanol oxidation reaction (825 mA mgPt -1 ). This study provides deep insights into the structure-performance relationship of PtSn/metal oxide composite catalysts, which would be helpful for the future design and fabrication of high-performance Pt-based ethanol oxidation reaction catalysts.

High Chemical Potential Driven Amorphization of Pd-based Nanoalloys.

Amorphous metals and alloys are promising candidates for superior catalysts in many catalytic and electrocatalytic reactions. It is of great urgency to develop a general method to construct amorphous alloys and further clarify the growth mechanism in a wet-chemical system. Herein, inspired by the conservation of energy during the crystallization process, amorphous PdCu nanoalloys have been successfully synthesized by promoting the chemical potential of the building blocks in solution. Benefiting from the abundant active sites and enhanced corrosion resistance, the synthesized amorphous PdCu nanostructures exhibit superior catalytic activity and durability over the face-centered cubic one in formic acid decomposition reaction. More importantly, the successful fabrications of amorphous PdFe, PdCo, and PdNi further demonstrate the universality of the above strategy. This proposed strategy is promising to diversify the amorphous family.

General Carbon-Supporting Strategy to Boost the Oxygen Reduction Activity of Zeolitic-Imidazolate-Framework-Derived Fe/N/Carbon Catalysts in Proton Exchange Membrane Fuel Cells.

The oxygen reduction reaction (ORR) activity of the Fe/N/Carbon catalysts derived from the pyrolysis of zeolitic-imidazolate-framework-8 (ZIF-8) has been still lower than that of commercial Pt-based catalysts utilized in the proton exchange membrane fuel cells (PEMFCs) due to low density of accessible active sites. In this study, an efficient carbon-supporting strategy is developed to enhance the ORR efficiency of the ZIF-derived Fe/N/Carbon catalysts by increasing the accessible active site density. The enhancement lies in (i) improving the accessibility of active sites via converting dodecahedral particles to graphene-like layered materials and (ii) enhancing the density of FeNx active sites via suppressing the formation of nanoparticles as well as providing extra spaces to host active sites. The optimized and efficient Fe/N/Carbon catalyst shows a half-wave potential (E1/2) of 0.834 V versus reversible hydrogen electrode in acidic media and produces a peak power density of 0.66 W cm-2 in an air-fed PEMFC at 2 bar backpressure, outperforming most previously reported Pt-free ORR catalysts. Finally, the general applicability of the carbon-supporting strategy is confirmed using five different commercial carbon blacks. This work provides an effective route to derive Fe/N/Carbon catalysts exhibiting a higher power density in PEMFCs.

Rifamycins do not function by allosteric modulation of binding of Mg2+ to the RNA polymerase active center.

Rifamycin antibacterial agents inhibit bacterial RNA polymerase (RNAP) by binding to a site adjacent to the RNAP active center and preventing synthesis of RNA products >2-3 nt in length. Recently, Artsimovitch et al. [(2005) Cell 122:351-363] proposed that rifamycins function by allosteric modulation of binding of Mg(2+) to the RNAP active center and presented three lines of biochemical evidence consistent with this proposal. Here, we show that rifamycins do not affect the affinity of binding of Mg(2+) to the RNAP active center, and we reassess the three lines of biochemical evidence, obtaining results not supportive of the proposal. We conclude that rifamycins do not function by allosteric modulation of binding of Mg(2+) to the RNAP active center.

Synthesis of sandwich-like Co15Fe85@C/RGO multicomponent composites with tunable electromagnetic parameters and microwave absorption performance.

Magnetic particle/carbon hybrid structures are promising candidates for high performance microwave absorbing materials with light weight and strong absorption. However, it remains a great challenge to balance the permittivity and permeability to realize impedance matching and further improve their absorption bandwidth. Herein, an effective strategy is designed to fabricate sandwich-like Co15Fe85@C/RGO composites. By introducing RGO sheets in the hybrid structures, the electromagnetic parameters, impedance matching and microwave absorption properties of the final materials can be well controlled. The optimized Co15Fe85@C/RGO composite shows an excellent microwave absorption performance, the strongest reflection loss (RL) of the sample is up to -33.38 dB at 10.72 GHz with a matching thickness of 2.5 mm, and the effective bandwidth (RL < -10 dB) can reach 9.2 GHz (8.64-17.84 GHz). With a single thickness, such a wide absorption band is rarely reported. Their excellent performance can be ascribed to the synergetic effect of the chemical composition and unique sandwich-like structures, which will improve impendence matching and strong microwave attenuation constants of the composites. Our results provide a facile strategy for tuning the electromagnetic parameters and microwave absorption properties of magnetic metal/carbon hybrid structures.

Synthesis of u-channelled spherical Fex(CoyNi1-y)100-x Janus colloidal particles with excellent electromagnetic wave absorption performance.

Due to their distinctive structure, inherently anisotropic properties and broad applications, Janus colloidal particles have attracted tremendous attention and it is significant to synthesize high yield Janus colloidal particles in a cost-effective and reliable way. On the other hand, due to the expanded electromagnetic interference problems, it is highly desired to develop excellent electromagnetic wave absorbing materials with an ultra-wide absorption bandwidth for practical application. Herein, a confined liquid-solid redox reaction strategy has been developed to fabricate a series of Fex(CoyNi1-y)100-x ternary alloy particles. The as-prepared particles are in the form of u-channelled noncentrosymmetric spheres, one kind of Janus colloidal particles which have been rarely observed. Due to the combination and synergy effects of multi-magnetic metals, the polycrystalline structure and their specific morphology, the as-prepared particles possess multiple magnetic resonance and multiple dielectric relaxation processes, and therefore show excellent electromagnetic wave absorption performances. In particular, the strongest reflection loss (RL) of the Fe15(Co0.2Ni0.8)85 Janus colloidal particles is up to -36.9 dB with a thickness of 2.5 mm, and the effective absorption (RL < -10 dB) bandwidth can reach 9.2 GHz (8-17.2 GHz) with a thickness of 2 mm. Such a wide bandwidth has barely been reported for magnetic metal alloys under a single thickness. These results suggest that the Fex(CoyNi1-y)100-x Janus particles could be a promising candidate for highly efficient electromagnetic wave absorbing materials for practical application.

Chemically initiated liquid-like behavior and fabrication of periodic wavy Cu/CuAu nanocables with enhanced catalytic properties.

Solid crystalline materials have long range order in their atomic arrangement while liquids have short range order, and the transition between them is usually caused by heat and/or pressure. Herein, we report the finding that chemical processes may play a similar role as heat and initiate liquid-like behavior of crystalline nanomaterials at a temperature far below their melting points. When the straight Cu/CuAu crystalline nanocables are dispersed in organic amine at 80 °C under ambient conditions, the continuous oxidation of Cu atoms on the surface and diffusion of Cu atoms from the core to the surface would break up the long-range ordered arrangement of atoms and lead to the transformation of an anisotropic crystal into an isotropic liquid-like state, which resulted in the evolution of the straight morphology of the nanocables into periodic wavy structures following the Rayleigh instability. It was also demonstrated that periodic wavy Cu@CuAu nanocables exhibit much better catalytic activity than straight Cu@CuAu nanocables towards the reduction of p-nitrophenol into p-aminophenol by NaBH4. Our results not only provide new insights into the transition between a solid crystal and a liquid-like state at the nanoscale, but also facilitate the development of new strategies for the synthesis of functional nanomaterials.

Liver receptor homologue-1 regulates gonadotrope function.

Over the past decade, substantial advances have been made in our understanding of the transcription factors which regulate gene expression in gonadotropes. One of the most important of these factors, steroidogenic factor-1 (SF-1; NR5A1) is critical for gonadotropin and GnRH-receptor expression. Interestingly, a closely related nuclear hormone receptor, liver receptor homologue-1 (LRH-1; NR5A2) has recently been detected in the anterior pituitary gland; however, its functional significance in this tissue has not been investigated. For the experiments reported here, we hypothesized that LRH-1 plays a previously unrecognized role in gonadotrope physiology. Towards this end, we first demonstrate LRH-1 mRNA and protein expression in both primary pituitary cells and gonadotrope-derived cell lines. We next show that LRH-1 stimulates promoter activity of the GnRH-receptor and gonadotropin subunit genes. Within the LHbeta gene, this response appears to be mediated by DNA-binding and transactivation through previously characterized SF-1 cis-elements. To our knowledge, this is the first report demonstrating a functional role for LRH-1 in the gonadotrope population of the anterior pituitary gland.

Controlled Encapsulation of Flower-like Rh-Ni Alloys with MOFs via Tunable Template Dealloying for Enhanced Selective Hydrogenation of Alkyne.

For new composite materials with functional nanoparticles (NPs) embedded in metal organic frameworks (MOFs), rational design and precise control over their architectures are imperative for achieving enhanced performance and novel functions. Especially in catalysis, the activity and selectivity of such composite materials are strongly determined by the encapsulation state and thickness of the MOF shell, which greatly influences the diffusion and adsorption of substance molecules onto the NP surface. In this study, MOF-74(Ni)-encapsulated Rh-Ni hierarchical heterostructures (Rh-Ni@MOF-74(Ni)) were successfully constructed using magnetic Rh-Ni-alloyed nanoflowers (NFs) as a self-sacrificial template. Strikingly, the encapsulation state and thickness of the formed MOF shell were well-tuned via template dealloying by changing the Ni content in the Rh-Ni NFs template. More interestingly, such unique Rh-Ni composites encapsulated with MOFs as catalysts could be magnetically recyclable and exhibited enhanced catalytic performance for the selective hydrogenation of alkynes to cis products, owing to the confinement effect of the MOF shell, as compared to their pristine counterparts.

Pituitary homeobox 1 (Pitx1) stimulates rat LHbeta gene expression via two functional DNA-regulatory regions.

Luteinizing hormone (LH) plays a central role in the reproductive axis, stimulating both gonadal steroid biosynthesis and the development of mature gametes. Over the past decade, significant progress has been made in characterizing the transcription factors and associated DNA-regulatory sites which mediate expression of the LH beta-subunit gene (LHbeta). One of these factors, pituitary homeobox 1 (Pitx1), has been shown to stimulate LHbeta gene promoter activity, both alone and in synergy with the orphan nuclear receptor, steroidogenic factor-1 (SF-1), and the early growth response gene 1 (Egr-1). Prior reports have attributed the Pitx1 response to a cis-element located at position -101 in the rat LHbeta gene promoter. While investigating the role of Pitx1 in regulating rat LHbeta gene expression, we observed a small, but significant, residual Pitx1 response despite mutation or deletion of this site. In the studies presented here, we identify the presence of a second functional Pitx1 region spanning positions -73 to -52 in the rat LHbeta gene promoter. Based on electrophoretic mobility shift assay, Pitx1 binds to both the initially described 5'Pitx1 site as well as this putative 3'Pitx1 region. In transient transfection analysis, mutation of the LHbeta-3'Pitx1 site significantly blunted Pitx1 responsiveness, with elimination of the Pitx1 response in a construct containing mutations in both Pitx1 cis-elements. We also analyzed the importance of each of these Pitx1 sites for providing functional synergy with SF-1 and with Egr-1. We observed a markedly decreased synergistic response with mutation of the 5'Pitx1 site with further loss following mutation of the 3'Pitx1 site. In contrast, functional interaction between Pitx1 and Egr-1 persisted with mutation of both Pitx1 regions. We conclude that Pitx1 stimulates the rat LHbeta gene promoter via two Pitx1 DNA-regulatory regions. These results further our understanding of the molecular mechanisms that regulate expression of this critical reproductive gene promoter.