Carbon nanofiber (CNF) papers have been widely used in many renewable energy systems, and the development of its catalytic function is of great significance and a major challenge. In this work, we pioneer a time- and cost-efficient strategy for the preparation of large-area flexible CNF films with uniformly distributed diatomic FeN3-CoN3 sites (Fe1Co1-CNF). Due to the excellent compatibility and similar functionality of the pre-designed ZnFeCo-NC precursors (ZnFeCo-pre) with the electrospun polymer polyacrylonitrile (PAN), the mixture of ZnFeCo-pre and PAN can be co-electrospun and subject to a standard CNF fabrication process. The resulting Fe1Co1-CNF exhibits excellent bifunctional catalytic performance for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), attributing to the abundant dual catalytic FeN3-CoN3 sites which are mutually beneficial for attaining optimal electronic properties for the adsorption/desorption of reaction intermediates. The assembled liquid-electrolyte ZAB provides a high specific power of 201.7 mW cm−2 and excellent cycling stability. More importantly, due to the good mechanical strength and flexibility of Fe1Co1-CNF, portable ZAB with exceptional shape deformability and stability can be demonstrated, in which Fe1Co1-CNF utility as an integrated free-standing membrane electrode. These findings provide a facile strategy for manufacturing flexible multi-functional catalytic electrodes with high production. [Display omitted] •Large-area self-standing flexible CNF film with diatomic Fe-Co sites was developed.•The diatomic Fe-Co sites render optimized adsorption of O-containing intermediates.•The Fe1Co1-CNF exhibits superior bifunctional ORR/OER performance.•The Fe1Co1-CNF shows great potential in liquid/flexible Zn-air battery.
•Non-precious catalysts for production of syngas from CO2 dry reforming of methane.•Extensive review of Ni-based bimetallic and transition metal phosphides.•Fundamental mechanisms of anti-coking and stability of catalysts in DRM reactions.•Recommendation of future research directions in non-precious catalysts for DRM. It is worthwhile to invest in the development of CO2 reforming of methane, as it presents a promising alternative for transforming two global warming gases into a very versatile product such as syngas. A syngas rich feed gas presents extensive prospects for existing downstream industrial processes for producing valuable fuels and chemicals. The commercialization of the DRM process greatly depends upon the development of low cost, non-precious transition metal-based catalysts, to provide a desirable balance between catalytic activity and stability. In this review, the progress in the advancements of non-precious catalytic materials have been discussed from a theoretical point of view. A theoretical perspective gives an opportunity to gain fundamental information at the atomic level, such as the interaction of reaction intermediates with particular crystal facets (typically active sites in the reaction), combined with electronic structure insights, directly influencing the kinetic behaviour of the catalyst system. Theoretical insights into the DRM reaction mechanisms on non-precious Ni-based bimetallic and transition metal phosphide catalysts are extensively discussed, together with the mitigation mechanisms to avoid carbon deposition and catalyst deactivation under DRM reaction conditions. Prospects of future development of DRM are also provided, highlighting the importance of computational chemistry studies in the development of the next-generation advanced DRM catalysts.
The development of catalytic materials for the recycling CO₂ through a myriad of available processes is an attractive field, especially given the current climate change. While there is increasing publication in this field, the reported catalysts rarely deviate from the traditionally supported metal nanoparticle morphology, with the most simplistic method of enhancement being the addition of more metals to an already complex composition. Encapsulated catalysts, especially yolk@shell catalysts with hollow voids, offer answers to the most prominent issues faced by this field, coking and sintering, and further potential for more advanced phenomena, for example, the confinement effect, to promote selectivity or offer greater protection against coking and sintering. This work serves to demonstrate the current position of catalyst development in the fields of thermal CO₂ reforming and hydrogenation, summarizing the most recent work available and most common metals used for these reactions, and how yolk@shell catalysts can offer superior performance and survivability in thermal CO₂ reforming and hydrogenation to the more traditional structure. Furthermore, this work will briefly demonstrate the bespoke nature and highly variable yolk@shell structure. Moreover, this review aims to illuminate the spatial confinement effect and how it enhances yolk@shell structured nanoreactors is presented.
The development of catalytic materials for the recycling CO2 through a myriad of available processes is an attractive field, especially given the current climate change. While there is increasing publication in this field, the reported catalysts rarely deviate from the traditionally supported metal nanoparticle morphology, with the most simplistic method of enhancement being the addition of more metals to an already complex composition. Encapsulated catalysts, especially yolk@shell catalysts with hollow voids, offer answers to the most prominent issues faced by this field, coking and sintering, and further potential for more advanced phenomena, for example, the confinement effect, to promote selectivity or offer greater protection against coking and sintering. This work serves to demonstrate the current position of catalyst development in the fields of thermal CO2 reforming and hydrogenation, summarizing the most recent work available and most common metals used for these reactions, and how yolk@shell catalysts can offer superior performance and survivability in thermal CO2 reforming and hydrogenation to the more traditional structure. Furthermore, this work will briefly demonstrate the bespoke nature and highly variable yolk@shell structure. Moreover, this review aims to illuminate the spatial confinement effect and how it enhances yolk@shell structured nanoreactors is presented.
We present a novel framework for simulating matrix models on a quantum computer. Supersymmetric matrix models have natural applications to superstring/M-theory and gravitational physics, in an appropriate limit of parameters. Furthermore, for certain states in the Berenstein-Maldacena-Nastase (BMN) matrix model, several supersymmetric quantum field theories dual to superstring/M-theory can be realized on a quantum device. Our prescription consists of four steps: regularization of the Hilbert space, adiabatic state preparation, simulation of real-time dynamics, and measurements. Regularization is performed for the BMN matrix model with the introduction of energy cut-off via the truncation in the Fock space. We use the Wan-Kim algorithm for fast digital adiabatic state preparation to prepare the low-energy eigenstates of this model as well as thermofield double state. Then, we provide an explicit construction for simulating real-time dynamics utilizing techniques of block-encoding, qubitization, and quantum signal processing. Lastly, we present a set of measurements and experiments that can be carried out on a quantum computer to further our understanding of superstring/M-theory beyond analytic results.
The β decay of 192Re117, which lies near the boundary between the regions of predicted prolate and oblate deformations, has been investigated using the KEK Isotope Separation System (KISS) in RIKEN Nishina Center. This is the first case in which a low-energy beam of rhenium isotope has been successfully extracted from an argon gas-stopping cell using a laser-ionization technique, following production via multi-nucleon transfer between heavy ions. The ground state of 192Re has been assigned Jπ=(0−) based on the observed β feedings and deduced logft values towards the 0+ and 2+ states in 192Os, which is known as a typical γ-soft nucleus. The shape transition from axial symmetry to axial asymmetry in the Re isotopes is discussed from the viewpoint of single-particle structure using the nuclear Skyrme-Hartree-Fock model.
Lithium–sulfur batteries (LSBs) are a class of new‐generation rechargeable high‐energy‐density batteries. However, the persisting issue of lithium polysulfides (LiPs) dissolution and the shuttling effect that impedes the efficiency of LSBs are challenging to resolve. Herein a general synthesis of highly dispersed pyrrhotite Fe1−xS nanoparticles embedded in hierarchically porous nitrogen‐doped carbon spheres (Fe1−xS‐NC) is proposed. Fe1−xS‐NC has a high specific surface area (627 m2 g−1), large pore volume (0.41 cm3 g−1), and enhanced adsorption and electrocatalytic transition toward LiPs. Furthermore, in situ generated large mesoporous pores within carbon spheres can accommodate high sulfur loading of up to 75%, and sustain volume variations during charge/discharge cycles as well as improve ionic/mass transfer. The exceptional adsorption properties of Fe1−xS‐NC for LiPs are predicted theoretically and confirmed experimentally. Subsequently, the electrocatalytic activity of Fe1−xS‐NC is thoroughly verified. The results confirm Fe1−xS‐NC is a highly efficient nanoreactor for sulfur loading. Consequently, the Fe1−xS‐NC nanoreactor performs extremely well as a cathodic material for LSBs, exhibiting a high initial capacity of 1070 mAh g−1 with nearly no capacity loss after 200 cycles at 0.5 C. Furthermore, the resulting LSBs display remarkably enhanced rate capability and cyclability even at a high sulfur loading of 8.14 mg cm−2.
Here, we report the synthesis of mesoporous ZnO/Ni@m-SiO2 yolk-shell particles. The unique ZnO/Ni@m-SiO2 catalysts demonstrate impressive resistance to sintering and coking for dry reforming of methane (DRM). They also display long term stability with high levels of conversion and selectivity, making this catalyst promising for chemical CO2 upgrading.
Encapsulation of metal nanoparticles is a leading technique used to inhibit the main deactivation mechanisms in dry reforming of methane reaction (DRM): Carbon formation and Sintering. Ni catalysts (15%) supported on alumina (Al2O3) and ceria (CeO2) have shown they are no exception to this analysis. The alumina supported catalysts experienced graphitic carbonaceous deposits, whilst the ceria showed considerable sintering over 15 h of DRM reaction. The effect of encapsulation compared to that of the performance of uncoated catalysts for DRM reaction has been examined at different temperatures, before conducting longer stability tests. The encapsulation of Ni/ZnO cores in silica (SiO2) leads to advantageous conversion of both CO2 and CH4 at high temperatures compared to its uncoated alternatives. This work showcases the significance of the encapsulation process and its overall effects on the catalytic performance in chemical CO2 recycling via DRM.
It is a challenging task to promote the activity and selectivity of a catalyst via precisely engineering the microenvironment, an important factor related with the catalytic performance of natural catalysts. Motivated by the water effect in promoting the catalytic activity explored in this work, a nanoreactor modified with phosphine ligand enabled the efficient hydrogenation of benzoic acid (BA) over Ru nanoparticles (NPs) in organic solvent under mild conditions, which cannot be achieved in unmodified nanoreactors. Both density functional theory (DFT) calculations and catalytic performance tests showed that the phosphine ligands can manipulate the adsorption strength of BA on Ru NPs by tuning the surface properties as well as preferentially interacting with the carboxyl of BA. The insights obtained in the present study provide a novel concept of nanoreactor design by anchoring ligands near catalytically active centers. A nanoreactor modified with a phosphine ligand enabled the efficient hydrogenation of benzoic acid (BA) over Ru nanoparticles in organic solvent under mild conditions. This cannot be achieved in unmodified nanoreactors; the phosphine ligands can manipulate the adsorption strength of BA on Ru NPs.
Supported bimetallic catalysts have become an important class of catalysts in heterogeneous catalysis. Although well-defined bimetallic nanoparticles (BNPs) can be synthesized by seeded-growth in liquid phase, uniform deposition of these BNPs onto porous supports is very challenging. Here, we develop a universal nanoreactor strategy to directly fabricate the PdAu BNPs in the solid support of coral-like nitrogen-doped mesoporous polymer (NMP) with uniform dispersion in a large scale. This strategy is based on coordination chemistry to introduce the high-quality seeds of Pd nanoclusters and the Au ions into the NMP, and thus to be used as a nanoreactor for seeded growth of PdAu BNPs in solid state during thermal reduction. Many other supported Pd-based BNPs (diameters ranging from 2 to 3 nm) have also been successfully synthesized by adoption of this strategy, including PdRu, PdCo, PdNi, PdZn, PdAg and PdCu BNPs. As an example, the as-synthesized Pd1Au1/4 sample shows enhanced catalytic performance in formic acid (FA) dehydrogenation compared with the monometallic analogues, indicating the synergistic effect between Pd and Au. In addition, the Pd1Au1/4 product is molded into monolith without any binders due to its coral-like structure. The Pd1Au1/4 monolith shows considerable activity in FA dehydrogenation with a turnover frequency (TOF) value of 3684 h−1 at 333 K, which is recycled five times without changes in activity. We believe that the nanoreactor strategy provides an effective route to synthesize various supported bimetallic catalysts that have potential for applications in green and sustainable catalytic processes.
We propose a new framework for simulating U(k) Yang-Mills theory on a universal quantum computer. This construction uses the orbifold lattice formulation proposed by Kaplan, Katz, and Unsal, who originally applied it to supersymmetric gauge theories. Our proposed approach yields a novel perspective on quantum simulation of quantum field theories, carrying certain advantages over the usual Kogut-Susskind formulation. We discuss the application of our constructions to computing static properties and real-time dynamics of Yang-Mills theories, from glueball measurements to AdS/CFT, making use of a variety of quantum information techniques including qubitization, quantum signal processing, Jordan-Lee-Preskill bounds, and shadow tomography. The generalizations to certain supersymmetric Yang-Mills theories appear to be straightforward, providing a path towards the quantum simulation of quantum gravity via holographic duality.
Fifty-five inclusive single nucleon removal cross sections from medium mass neutron-rich nuclei impinging on a hydrogen target at 250 MeV/nucleon were measured at the RIKEN Radioactive Isotope Beam Factory. Systematically higher cross sections are found for proton removal from nuclei with an even number of protons compared to odd-proton number projectiles for a given neutron separation energy. Neutron removal cross sections display no even-odd splitting contrary to nuclear cascade model predictions. Both effects are understood through simple considerations of neutron separation energies and bound state level densities originating in pairing correlations in the daughter nuclei. These conclusions are supported by comparison with semi-microscopic model predictions,highlighting the enhanced role of low-lying level densities in nucleon removal cross sections from loosely-bound nuclei.
Over the past decade, considerable progress has been made in the synthesis and applications of nanoporous carbon spheres ranging in size from nanometres to micrometres. This Review presents the primary techniques for preparing nanoporous carbon spheres and the seminal research that has inspired their development, presented potential applications and uncovered future challenges. First we provide an overview of the synthesis techniques, including the Stöber method and those based on templating, self-assembly, emulsion and hydrothermal carbonization, with special emphasis on the design and functionalization of nanoporous carbon spheres at the molecular level. Next, we cover the key applications of these spheres, including adsorption, catalysis, separation, energy storage and biomedicine — all of which might benefit from the regular geometry, good liquidity, tunable porosity and controllable particle-size distribution offered by nanoporous carbon spheres. Finally, we present the current challenges and opportunities in the development and commercial applications of nanoporous carbon spheres.
The CO₂ methanation is an important process in coal-to-gas, power-to-gas and CO₂ removal for spacecraft. Recently, metal-organic framework (MOF) derivatives have been demonstrated as high-performance catalysts for CO₂ upgrading processes. However, due to the high costs and low stability of MOF derivatives, it still remains challenge for the development of alternative synthesis methods avoiding MOF precursors. In this work, we present the sol-gel method for loading Ni-MOF to silica support in two-steps. Upon modifying the procedure, a more simplified one-step sol-gel method has been developed. Furthermore, the obtained Ni/SiO₂ catalyst still exhibits great catalytic performance with a CO₂ conversion of 77.2% and considerable CH4 selectivity of ~100% during a stability test for 52 h under a low temperature of 310 °C and high GHSV of 20,000 mL·g−1·h−1. Therefore, this work provides a ground-breaking direct strategy for loading MOF derived catalysts, and might shed a light on the preparation of highly dispersed Ni/SiO₂ catalyst.
In heterogeneous catalysis, the precise placement of active components to perform unique functions in cooperation with each other is a tremendous challenge. The migration of matter on micro/nano-scale caused by diffusion is a promising pathway for design of catalytic nanoreactors with precise active sites location and controllable microenvironment through compartmentalization and confinement effects. Herein, we report two categories of mesoporous ZnCoSiOx hollow nanoreactors with different metal distributions and microenvironment engineered by the diffusion behavior of metal species in confined nanospace. Double-shelled hollow structures with well-distributed metal species were obtained by adopting core@shell structured ZnCo-zeolitic imidazolate framework (ZIF)@SiO2 as a template and employing three stages of hydrothermal treatment including the decomposition of ZIF, diffusion of metal species into the silica shell, and Ostwald ripening. Additionally, the formation of yolk@shell structure with a collective (Zn-Co) metal oxide as the yolk was achieved by direct pyrolysis of ZnCo-ZIF@SiO2. In CO2 hydrogenation, ZnCoSiOx with double-shelled hollow structures and yolk@shell structures respectively afford CO and CH4 as main product, which is related with different dispersion and location of active sites in the two catalysts. This study provides an efficient method for the synthesis of catalytic nanoreactors on the basis of insights of the atomic diffusion in confined space at the mesoscale.
β-decay spectroscopy of 173,174Ho (Z = 67, N = 106,107) was conducted at Radioactive Isotope Beam Factory at RIKEN by using in-flight fission of a 345-MeV/u 238U primary beam. A previously unreported isomeric state at 405 keV with half-life of 3.7(12) μs and a spin and parity of (3/2+) is identified in 173Ho. Moreover, a new state with a spin and parity of 9- was discovered in 174Er. The experimental log ft values of 5.84(20) and 5.25(18) suggest an allowed-hindered β decay from the ground state of 174Ho to the Kπ = 8- isomeric state in 174Er. Configuration-constrained potential energy surface (PES) calculations were performed and the predictions are in reasonable agreement with the experimental results.
The hydrogenation of levulinic acid to γ-valerolactone with water as solvent is a crucial reaction for producing fine chemicals. However, the development of highly stable catalysts is still a major challenge. Here, we prepared a Ru nanoparticles incorporated in mesoporous-carbon (Ru-MC) catalyst to achieve high stability in acidic aqueous medium. The Ru-MC showed excellent catalytic performance (12024h-1 turnover frequency) in the hydrogenation of LA-to3 GVL. Compared with Ru supported on mesoporous carbon catalyst (Ru/MC) prepared by conventional wet impregnation method, the Ru-MC showed excellent reusability (more than 6 times) and thermal stability (up to 600 oC). Based on H2-TPR-MS characterization, it was proposed that the incorporated structure significantly increased the interaction between Ru nanoparticles and carbon support, which effectively prevent the leaching and sintering of Ru nanoparticles and contributed to increased high reusability and thermal stability of the Ru-MC.
This work reports the successful and simplistic synthesis of highly uniform NiCo@SiO₂ yolk@shell catalysts, with their effectiveness towards CO₂ recycling investigated within the RWGS reaction. The engineered microstructure catalysts display high CO₂ conversion levels and a remarkable selectivity for CO as main reaction product across the whole examined temperatures. Interestingly, the selectivity is affected by Ni loading reflecting a close correlation catalytic performance/material structure-composition. Further to this behaviour, the designed nanoreactor exhibits considerable deactivation resistance and performance under reaction cycling conditions and appears to demonstrate the production of larger organic molecules after qualitative analysis of the product gas by mass spectrometry. These results demonstrate the effectiveness of the spatial confinement effect, imbued to the material from its advanced morphology, through its influence of deactivation resistance and control of reactive selectivity.
A series of reactive blends, comprising a commercial benzoxazine monomer, 2,2-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane, and bisphenol A is prepared and characterized. Thermal analysis and dynamic rheology reveal how the introduction of up to 15 wt % bisphenol A lead to a significant increase in reactivity (the exothermic peak maximum of thermal polymerization is reduced from 245 °C to 215 °C), with a small penalty in glass transition temperature (reduction of 15 K), but similar thermal stability (onset of degradation = 283 °C, char yield = 26%). With higher concentrations of bisphenol A (e.g. 25 wt %), a significantly more reactive blend is produced (exothermic peak maximum = 192 °C), but with a significantly lower thermal stability (onset of degradation = 265 °C, char yield = 22%) and glass transition temperature (128 °C). Attempts to produce a cured plaque containing 35 wt % bisphenol A were unsuccessful, due to brittleness. Molecular modelling is used to replicate successfully the glass transition temperatures (measured using thermal analysis) of a range of copolymers.