Compressive strain in Cu catalysts: Enhancing generation of C2+ products in electrochemical CO2 reduction.

Elastic strain in Cu catalysts enhances their selectivity for the electrochemical CO2 reduction reaction (eCO2RR), particularly toward the formation of multicarbon (C2+) products. However, the reasons for this selectivity and the effect of catalyst precursors have not yet been clarified. Hence, we employed a redox strategy to induce strain on the surface of Cu nanocrystals. Oxidative transformation was employed to convert Cu nanocrystals to CuxO nanocrystals; these were subsequently electrochemically reduced to form Cu catalysts, while maintaining their compressive strain. Using a flow cell configuration, a current density of 1 A/cm2 and Faradaic efficiency exceeding 80% were realized for the C2+ products. The selectivity ratio of C2+/C1 was also remarkable at 9.9, surpassing that observed for the Cu catalyst under tensile strain by approximately 7.6 times. In-situ Raman and infrared spectroscopy revealed a decrease in the coverage of K+ ion-hydrated water (K·H2O) on the compressively strained Cu catalysts, consistent with molecular dynamics simulations and density functional theory calculations. Finite element method simulations confirmed that reducing the coverage of coordinated K·H2O water increased the probability of intermediate reactants interacting with the surface, thereby promoting efficient C-C coupling and enhancing the yield of C2+ products. These findings provide valuable insights into targeted design strategies for Cu catalysts used in the eCO2RR.

A theoretical study on hydrated sodium ion-phenylalanine clusters Na+(Phe)(H2O)n (n = 0-6; Phe = phenylalanine).

The cation-π interaction is of importance in many chemical and biological processes such as those involving protein geometries and functionals and ion channels. In this study, to understand the cation-π interaction between essential ions and protein in the water-aqueous environment, geometries, electronic structures, bonding properties, and dynamic stabilities of hydrated Na+-phenylalanine clusters Na+(Phe)(H2O)n (n = 0-6) were studied using density functional theory calculations and ab initio molecular dynamics simulations. After the addition of water molecules, Na+(Phe)(H2O)n structures change from a tridentate complex to quadridentate or pentadentate complexes while the cation-π interaction always exists. The fluctuation between quadridentate and pentadentate complexes results from the competition between cation-O bonding and hydrogen bonding. The charge analysis reveals that the positive charge is mainly located on the Na ion, whereas the further addition of water reduces the binding energy of water, electron affinity, and ionization potential. As the number of water molecules increases, the bonding interactions between the sodium ion and the remaining phenylalanine-water complex increase and correlate with the coordination number, in which the electrostatic interaction contributes more than the orbital interaction. The important orbital interaction terms come from the donation of the carboxyl and amino groups and water to the Na+ ion. Molecular dynamic simulations revealed that Na+(Phe)(H2O)6 is stable at 300 K.

Deep mineralization of VOCs in an embedded hybrid structure CoFe2O4/MoS2/PMS wet scrubber system.

Peroxymonosulfate (PMS)-based advanced oxidation processes in liquid phase systems can actively degrade toluene. In this work, the catechol structural surfactant was introduced to synthesize the dispersed and homogeneous CoFe2O4 nanospheres and embedded into MoS2 nanoflowers to form magnetically separable heterojunction catalysts. The innovative approach effectively mitigated the traditionally low reduction efficiency of transition metal ions during the heterogeneous activation process. In CoFe2O4/MoS2/PMS system, the toluene removal efficiency remained 95% within 2 h. The contribution of SO4⋅-, ·O2-, ·OH, and 1O2 was revealed by radical quenching experiment and electron paramagnetic resonance spectroscopy. The results illustrated that MoS2 offers ample reduction sites for facilitating PMS activation via Fe3+/Fe2+ redox interactions. Furthermore, an investigation into the toluene degradation pathway within the CoFe2O4/MoS2/PMS system revealed its capability to suppress the formation of toxic byproducts. This ambient-temperature liquid-phase method presented promising route for the removal of industrial volatile organic pollutants.

Controlled Growth Cu2S Nanoarrays with High-Performance Photothermal Properties.

The controlled growth of Cu2S nanoarrays was constructed by a facile two-step impregnation synthesis route. The as-synthesized Cu2S/CuO@Cu samples were precisely characterized in terms of surface morphology, phase, composition, and oxidation states. At the laser irradiation of 808 nm, Cu2S/CuO@Cu heated up to 106 °C from room temperature in 120 s, resulting in an excellent photothermal conversion performance. The Cu2S/CuO@Cu exhibited excellent cycling performance-sustaining the photothermal performance during five heating-cooling cycles. The finite difference time domain (FDTD) simulation of optical absorption and electric field distributions assured the accuracy and reliability of the developed experimental conditions for acquiring the best photothermal performance of Cu2S/CuO@Cu.

Wearable Noninvasive Glucose Sensor Based on CuxO NFs/Cu NPs Nanocomposites.

Designing highly active material to fabricate a high-performance noninvasive wearable glucose sensor was of great importance for diabetes monitoring. In this work, we developed CuxO nanoflakes (NFs)/Cu nanoparticles (NPs) nanocomposites to serve as the sensing materials for noninvasive sweat-based wearable glucose sensors. We involve CuCl2 to enhance the oxidation of Cu NPs to generate Cu2O/CuO NFs on the surface. Due to more active sites endowed by the CuxO NFs, the as-prepared sample exhibited high sensitivity (779 µA mM-1 cm-2) for noninvasive wearable sweat sensing. Combined with a low detection limit (79.1 nM), high selectivity and the durability of bending and twisting, the CuxO NFs/Cu NPs-based sensor can detect the glucose level change of sweat in daily life. Such a high-performance wearable sensor fabricated by a convenient method provides a facile way to design copper oxide nanomaterials for noninvasive wearable glucose sensors.

Vesicular self-assembly of copolymer-grafted nanoparticles with anisotropic shapes.

Plasmonic nanovesicles show broad applications in areas such as cancer theranostics and drug delivery, but the preparation of nanovesicles from shaped nanoparticles remains challenging. This article describes the vesicular self-assembly of shaped nanoparticles, such as gold nanocubes grafted with amphiphilic block copolymers, in selective solvents. The nanocubes assembled within the vesicular membranes exhibit two distinctive packing modes, namely square-like and hexagonal packing, depending on the relative dimensions of the copolymer ligands and nanocubes. The corresponding optical properties of the plasmonic nanovesicles can be tuned by varying the length of the grafted copolymers and the size of the nanocubes. This work provides guidance for the fabrication of functional plasmonic vesicles for applications in catalysis, nanomedicines and optical devices.

Geometries, electronic structures, and bonding properties of endohedral Group-14 Zintl clusters TM@E10 (TM = Fe, Co, Ni; E = Ge, Sn, Pb).

The geometries, electronic structures, and bonding properties of the title endohedral Zintl clusters have been studied by using ab initio calculations. [Fe@Ge10 ]4- and [Co@Ge10 ]3- have D5h -symmetric pentagonal prismatic structure and [Fe@Sn10 ]4- adopts the C2v -symmetric structure as their ground-state structures, whereas all the other clusters possess D4d bicapped square antiprismatic structures, in consistent with the experimental values when available. Natural bonding orbital and electron localization function disclosed that the negative charges are localized on the central atoms rather than the cages while the TME ionic bonding interactions increase in the order of Ge < Sn < Pb. The energy decomposition analysis revealed that the total bonding energy ∆Eint between central TM and E10 cage is above 150 kcal/mol. The ionic bonding interaction termed as electrostatic interaction ∆Eelstat increases in the order of Ge < Sn < Pb and becomes higher than the covalent bonding interactions termed as total orbital interactions ∆Eorb . Among the total orbital interactions, the π back donations from the TM-d orbitals to the empty cage orbitals consisting of E-p orbitals, the magnitude of which is importantly affected by the cage symmetry, are dominant contributions.

Atomically ordered Rh2P catalysts anchored within hollow mesoporous carbon for efficient hydrogen production.

Atomically ordered Rh2P nanoclusters encapsulated within a high-surface-area hollow mesoporous carbon nanoreactor are catalytically active for hydrogen production via the electrocatalytic hydrogen evolution reaction and the room-temperature dehydrogenation of ammonia borane.

Endohedral group-14-element clusters TM@E9 (TM = Co, Ni, Cu; E = Ge, Sn, Pb) and their low-dimensional nanostructures: a first-principles study.

Endohedral group14-based clusters with the encapsulation of a transition metal, which are termed [TM@Em]n- (TM = transition metal and E = group-14 elements), have lots of potential applications and have been used as interesting building blocks in materials science. Nevertheless, their electronic structures and stability mechanism remain unclear. In this paper, we systematically study the geometries, electronic structures, and bonding properties of [TM@E9]n- clusters which are the smallest endohedral group-14-based clusters synthesized so far, by using density functional theory (DFT) calculations. The calculation results reveal the important role of TMs in affecting the structures and bonding interactions in the [TM@E9]n- cluster. In the presence of a TM, the cluster geometry could change from a monocapped square antiprism (C4v) for empty [E9]4- cages to a tricapped trigonal prismatic geometry (D3h) for [TM@E9]n-. By using the energy decomposition analysis (EDA) method, the bonding properties between the endohedral TM and E9 cluster have been thoroughly investigated. It was found that the origin of stability of these clusters is from the large electrostatic attraction with significantly reduced Pauli repulsion. In the case of orbital interactions, the π back-donations from d orbitals of the TM to the cluster make important contributions. More interestingly, the 1D-chain and 2D-sheet nanostructures based on the [Ni@E9] cluster have been theoretically predicted. The band structure and density of states analysis revealed that all of these nanostructures are metallic and their excellent thermodynamic stability has been confirmed by using ab initio molecular dynamics (AIMD) simulations.

CoFe Nanoparticle-Decorated Reduced Graphene Oxide for the Highly Efficient Reduction of 4-Nitrophenol.

High-performance, nonprecious metal catalysts with special morphologies and easy-to-recycle properties are essential for the treatment of environmental pollutants. Herein, CoFe nanoparticle-decorated reduced graphene oxide (RGO) catalysts were designed and successfully fabricated, and the catalyst was then used to reduce 4-nitrophenol into 4-aminophenol. Outstanding catalytic properties with a reduction rate constant of 4.613 min-1 were achieved due to the synergistic properties of the CoFe metal alloy and the high-conductivity RGO components in the catalysts. In addition, the catalyst was conveniently recovered via magnets due to its inherent magnetic properties. The facile preparation, outstanding catalytic performance, structural stability, and low material costs make the CoFe/RGO nanocatalyst a promising candidate for potential applications in catalysis.

Stable Noble Gas Compounds Based on Superelectrophilic Anions [B12 (BO)11 ]- and [B12 (OBO)11 ].

Superelectrophilic monoanions [B12 (BO)11 ]- and [B12 (OBO)11 ]- , generated from stable dianions [B12 (BO)12 ]2- and [B12 (OBO)12 ]2- , show great potential for binding with noble gases (Ngs). The binding energies, quantum theory of atoms in molecules (QTAIM), natural population analysis (NPA), energy decomposition analysis (EDA), and electron localization function (ELF) were carried out to understand the B-Ng bond in [B12 (BO)11 Ng]- and [B12 (OBO)11 Ng]- . The calculated results reveal that heavier noble gases (Ar, Kr, and Xe) bind covalently with both [B12 (BO)11 ]- and [B12 (OBO)11 ]- with large binding energies, making them potentially feasible to be synthesized. Only [B12 (OBO)11 ]- could form a covalent bond with helium or neon but the small binding energy of [B12 (OBO)11 He]- may pose a challenge for its experimental detection.

Ultrafine RhNi Nanocatalysts Confined in Hollow Mesoporous Carbons for a Highly Efficient Hydrogen Production from Ammonia Borane.

Ammonia borane (AB) has received growing research interest as one of the most promising hydrogen-storage carrier materials. However, fast dehydrogenation of AB is still limited by sluggish catalytic kinetics over current catalysts. Herein, highly uniform and ultrafine bimetallic RhNi alloy nanoclusters encapsulated within nitrogen-functionalized hollow mesoporous carbons (defined as RhNi@NHMCs) are developed as highly active, durable, and selective nanocatalysts for fast hydrolysis of AB under mild conditions. Remarkable activity with a high turnover frequency (TOF) of 1294 molH2 molRh-1 min-1 and low activation energy (Ea) of 18.6 kJ mol-1 is observed at room temperature, surpassing the previous Rh-based catalysts. The detailed mechanism studies reveal that when catalyzed by RhNi@NHMCs, a covalently stable O-H bond by H2O first cleaves in electropositive H* and further attacks B-H bond of AB to stoichiometrically produce 3 equiv of H2, whose catalytic kinetics is restricted by the oxidation cleavage of the O-H bond. Compositional and structural features of RhNi@NHMCs result in synergic electronic, functional, and support add-in advantages, kinetically accelerating the cleavage of the attacked H2O (O-H bond) and remarkably promoting the catalytic hydrolysis of AB accordingly. This present work represents a new and effective strategy for exploring high-performance supported metal-based alloy nanoclusters for (electro)catalysis.

Stabilities, Electronic Structures, and Bonding Properties of 20-Electron Transition Metal Complexes (Cp)2TMO and their One-Dimensional Sandwich Molecular Wires (Cp = C5H5, C5(CH3)H4, C5(CH3)5; TM = Cr, Mo, W).

First-principles calculations have been carried out for the 20-electron transition metal complexes (Cp)2TMO and their molecular wires (Cp = C5H5, C5(CH3)H4, C5(CH3)5; TM = Cr, Mo, W). The calculation results at the BP86/def2-TZVPP level reveal that the ground state is singlet and the optimized geometries are in good agreement with the experimental values. The analysis of frontier molecular orbitals shows that two electrons in the highest occupied molecular orbital HOMO-1 are mainly localized on cyclopentadienyl and oxygen ligands. Furthermore, the nature of the TM-O bond was investigated with the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV). The attraction term in the intrinsic interaction energies ΔEint is mainly composed of two important parts, including electrostatic interaction (about 52% of the total attractive interactions ΔEelstat + ΔEorb) and orbital interaction, which might be the major determinant of the stability of these (Cp)2TMO complexes. All of the TM-O bonds should be described as electron-sharing σ single bonds [(Cp)2TM]+-[O]- with the contribution of 53-57% of ΔEorb and two π backdonations from the occupied p orbitals of oxygen ligands into vacant π* MOs of the [(Cp)2TM]+ fragments, which are 35-40% of ΔEorb. The results of bond order and interaction energy from EDA-NOCV calculations suggest the influence of the radius of TM and methyl in the interactions between TM and O in (Cp)2TMO. Additionally, the relativistic effects slightly amplify the strength of bonding with increasing ΔEorb for the EDA-NOCV calculations on three metal complexes (C5H5)2TMO. Finally, the geometries, electronic structures, and magnetics of infinitely extended systems, [(C5H5)TMO]∞, have also been explored. The results of the density of states (DOS) and band structure revealed that [(C5H5)CrO]∞ and [(C5H5)WO]∞ are semiconductors with the narrow bands, whereas [(C5H5)MoO]∞ behaves as metal.

Synthesis and Crystal-Phase Engineering of Mesoporous Palladium-Boron Alloy Nanoparticles.

Rational design and synthesis of noble metal nanomaterials with desired crystal phases (atomic level) and controllable structures/morphologies (mesoscopic level) are paramount for modulating their physiochemical properties. However, it is challenging to simultaneously explore atomic crystal-phase structures and ordered mesoscopic morphologies. Here, we report a simple synergistic templating strategy for the preparation of palladium-boron (Pd-B) nanoparticles with precisely controllable crystal-phases and highly ordered mesostructures. The engineering of crystal-phase structures at atomic levels is achieved by interstitially inserting metallic B atoms into face-centered cubic mesoporous Pd (fcc-mesoPd) confined in a mesoporous silica template. With the gradual insertion of B atoms, fcc-mesoPd is transformed into fcc-mesoPd5B, hcp-mesoPd2B with randomly distributed B atoms (hcp-mesoPd2B-r), and hcp-mesoPd2B with an atomically ordered B sequence (hcp-mesoPd2B-o) while preserving well-defined mesostructures. This synergistic templating strategy can be extended to engineer crystal-phase structures with various mesostructures/morphologies, including nanoparticles, nanobundles, and nanorods. Moreover, we investigate the crystal-phase-dependent catalytic performance toward the reduction reaction of p-nitrophenol and find that hcp-mesoPd2B-o displays much better catalytic activity. This work thus paves a new way for the synthesis of hcp-Pd2B nanomaterials with mesoscopically ordered structure/morphology and offers new insights of fcc-to-hcp evolution mechanisms which could be applied on other noble metal-based nanomaterials for various targeted applications.

Stabilities, Electronic Structures, and Bonding Properties of Iron Complexes (E1E2)Fe(CO)2(CNArTripp2)2 (E1E2=BF, CO, N2, CN-, or NO+).

The coordination of 10-electron diatomic ligands (BF, CO N2) to iron complexes Fe(CO)2(CNArTripp2)2 [ArTripp2=2,6-(2,4,6-(iso-propyl)3C6H2)2C6H3] have been realized in experiments very recently (Science, 2019, 363, 1203-1205). Herein, the stability, electronic structures, and bonding properties of (E1E2)Fe-(CO)2(CNArTripp2)2 (E1E2=BF, CO, N2, CN-, NO+) were studied using density functional (DFT) calculations. The ground state of all those molecules is singlet and the calculated geometries are in excellent agreement with the experimental values. The natural bond orbital analysis revealed that Fe is negatively charged while E1 possesses positive charges. By employing the energy decomposition analysis, the bonding nature of the E2E1-Fe(CO)2(CNArTripp2)2 bond was disclosed to be the classic dative bond E2E1→Fe(CO)2(CNArTripp2)2 rather than the electron-sharing double bond. More interestingly, the bonding strength between BF and Fe(CO)2(CNArTripp2)2 is much stronger than that between CO (or N2) and Fe(CO)2(CNArTripp2)2, which is ascribed to the better σ-donation and π back-donations. However, the orbital interactions in CN-→Fe(CO)2(CNArTripp2)2 and NO+→Fe(CO)2(CNArTripp2)2 mainly come from σ-donation and π back-donation, respectively. The different contributions from σ donation and π donation for different ligands can be well explained by using the energy levels of E1E2 and Fe(CO)2(CNArTripp2)2 fragments.

Polymeric Ligand-Mediated Regioselective Bonding of Plasmonic Nanoplates and Nanospheres.

Nanoparticle (NP) clusters are attractive for many applications, but controllable and regioselective assembly of clusters remains challenging. This communication reports a strategy to precisely assemble Ag nanoplates (NP-As) and Au nanospheres (NP-Bs) grafted with copolymer ligands into defined ABx clusters with controlled coordination number (x) and orientation of the NPs. The directional bonding of shaped NPs relies on the stoichiometric reaction of complementary reactive groups on copolymer ligands. The x value of NP clusters can be tuned from 1 to 4 by varying the number ratio of reactive groups on single NP-Bs to NP-As. The regioselective bonding of nanospheres to the edge or face of a central nanoplate is governed by the steric hindrance of copolymeric ligands on the nanoplate. The clusters exhibit distinctive plasmonic properties that are dependent on the bonding modes of NPs. This study paves a route to fabricating nanostructures with high precision and complexity for applications in plasmonics, catalysis, and sensing.

Wearable, stable, highly sensitive hydrogel-graphene strain sensors.

A stable and highly sensitive graphene/hydrogel strain sensor is designed by introducing glycerol as a co-solvent in the formation of a hydrogel substrate and then casting a graphene solution onto the hydrogel in a simple, two-step method. This hydrogel-based strain sensor can effectively retain water in the polymer network due to the formation of strong hydrogen bonding between glycerol and water. The addition of glycerol not only enhances the stability of the hydrogel over a wider temperature range, but also increases the stretchability of the hydrogel from 800% to 2000%. The enhanced sensitivity can be attributed to the graphene film, whereby the graphene flakes redistribute to optimize the contact area under different strains. The careful design enables this sensor to be used in both stretching and bending modes. As a demonstration, the as-prepared strain sensor was applied to sense the movement of finger knuckles. Given the outstanding performance of this wearable sensor, together with the proposed scalable fabrication method, this stable and sensitive hydrogel strain sensor is considered to have great potential in the field of wearable sensors.

Localized surface plasmon enhanced electrocatalytic methanol oxidation of AgPt bimetallic nanoparticles with an ultra-thin shell.

AgPt bimetallic hollow nanoparticles (AgPt-BHNPs) with an ultra-thin shell were synthesized. They show obvious localized surface plasmon resonance (LSPR) effects on electrocatalytic activity and CO poisoning tolerance in the methanol oxidation reaction (MOR) in alkaline media, which is attributed to the LSPR-induced localized photothermal effects and LSPR induced surface charge heterogeneity.

Ion-Induced Synthesis of Alginate Fibroid Hydrogel for Heavy Metal Ions Removal.

Design and synthesis of environmentally friendly adsorbents with high adsorption capacities are urgently needed to control pollution of water resources. In this work, a calcium ion-induced approach was used to synthesize sodium alginate fibroid hydrogel (AFH). The as-prepared AFH has certain mechanical strength, and the mechanical strength is enhanced especially after the adsorption of heavy metal ions, which is very convenient for the recovery. AFH exhibited excellent adsorption performances for Cu2+, Cd2+, and Pb2+ ions and displayed very high saturated adsorption capacities (Qe) of 315.92 mg·g-1 (Cu2+), 232.35 mg·g-1 (Cd2+), and 465.22 mg·g-1 (Pb2+) with optimized pH values (3.0-4.0) and temperature (303 K). The study of isotherms and kinetics indicated that adsorption processes of heavy metal ions fitted well with the pseudo-second-order kinetics model and the Langmuir model. Pb2+ was found to have the strongest competitiveness among the three heavy metal ions. Thus, AFH has great application prospects in the field of heavy metal ions removing from wastewater.

Surfactant-free synthesis of Cu2O yolk-shell cubes decorated with Pt nanoparticles for enhanced H2O2 detection.

Pt decorated yolk-shell Cu2O cubes are obtained using a surfactant-free and multiple-step method. Porous yolk-shell cubic structures, together with synergistic effects between Pt and Cu2O, endow the yolk-shell Pt-Cu2O based nonenzymatic H2O2 sensors with enhanced sensing performance.