Enhancing Zinc Electrode Stability Through Pre-Desolvation and Accelerated Charge Transfer via a Polyimide Interface for Zinc-Ion Batteries.

Aqueous zinc-based energy storage devices possess superior safety, cost-effectiveness, and high energy density; however, dendritic growth and side reactions on the zinc electrode curtail their widespread applications. In this study, these issues are mitigated by introducing a polyimide (PI) nanofabric interfacial layer onto the zinc substrate. Simulations reveal that the PI nanofabric promotes a pre-desolvation process, effectively desolvating hydrated zinc ions from Zn(H2O)6 2+ to Zn(H2O)4 2+ before approaching the zinc surface. The exposed zinc ion in Zn(H2O)4 2+ provides an accelerated charge transfer process and reduces the activation energy for zinc deposition from 40 to 21 kJ mol-1. The PI nanofabric also acts as a protective barrier, reducing side reactions at the electrode. As a result, the PI-Zn symmetric cell exhibits remarkable cycling stability over 1200 h, maintaining a dendrite-free morphology and minimal byproduct formation. Moreover, the cell exhibits high stability and low voltage hysteresis even under high current densities (20 mA cm-2, 10 mAh cm-2) thanks to the 3D porous structure of PI nanofabric. When integrated into full cells, the PI-Zn||AC hybrid zinc-ion capacitor and PI-Zn||MnVOH@SWCNT zinc-ion battery achieve impressive lifespans of 15000 and 600 cycles with outstanding capacitance retention. This approach paves a novel avenue for high-performance zinc metal electrodes.

Defect Engineering Centrosymmetric 2D Material Flexocatalysts.

In this study, the flexoelectric characteristics of 2D TiO2 nanosheets are examined. The theoretical calculations and experimental results reveal an excellent strain-induced flexoelectric potential (flexopotential) by an effective defect engineering strategy, which suppresses the recombination of electron-hole pairs, thus substantially improving the catalytic activity of the TiO2 nanosheets in the degradation of Rhodamine B dye and the hydrogen evolution reaction in a dark environment. The results indicate that strain-induced bandgap reduction enhances the catalytic activity of the TiO2 nanosheets. In addition, the TiO2 nanosheets degraded Rhodamine B, with kobs being ≈1.5 × 10-2 min-1 in dark, while TiO2 nanoparticles show only an adsorption effect. 2D TiO2 nanosheets achieve a hydrogen production rate of 137.9 µmol g-1 h-1 under a dark environment, 197% higher than those of TiO2 nanoparticles (70.1 µmol g-1 h-1 ). The flexopotential of the TiO2 nanosheets is enhanced by increasing the bending moment, with excellent flexopotential along the y-axis. Density functional theory is used to identify the stress-induced bandgap reduction and oxygen vacancy formation, which results in the self-dissociation of H2 O on the surface of the TiO in the dark. The present findings provide novel insights into the role of TiO2 flexocatalysis in electrochemical reactions.

Dual-plasmonic Au@Cu7S4 yolk@shell nanocrystals for photocatalytic hydrogen production across visible to near infrared spectral region.

Near infrared energy remains untapped toward the maneuvering of entire solar spectrum harvesting for fulfilling the nuts and bolts of solar hydrogen production. We report the use of Au@Cu7S4 yolk@shell nanocrystals as dual-plasmonic photocatalysts to achieve remarkable hydrogen production under visible and near infrared illumination. Ultrafast spectroscopic data reveal the prevalence of long-lived charge separation states for Au@Cu7S4 under both visible and near infrared excitation. Combined with the advantageous features of yolk@shell nanostructures, Au@Cu7S4 achieves a peak quantum yield of 9.4% at 500 nm and a record-breaking quantum yield of 7.3% at 2200 nm for hydrogen production in the absence of additional co-catalysts. The design of a sustainable visible- and near infrared-responsive photocatalytic system is expected to inspire further widespread applications in solar fuel generation. In this work, the feasibility of exploiting the localized surface plasmon resonance property of self-doped, nonstoichiometric semiconductor nanocrystals for the realization of wide-spectrum-driven photocatalysis is highlighted.

Investigating the role of undercoordinated Pt sites at the surface of layered PtTe2 for methanol decomposition.

Transition metal dichalcogenides, by virtue of their two-dimensional structures, could provide the largest active surface for reactions with minimal materials consumed, which has long been pursued in the design of ideal catalysts. Nevertheless, their structurally perfect basal planes are typically inert; their surface defects, such as under-coordinated atoms at the surfaces or edges, can instead serve as catalytically active centers. Here we show a reaction probability > 90 % for adsorbed methanol (CH3OH) on under-coordinated Pt sites at surface Te vacancies, produced with Ar+ bombardment, on layered PtTe2 - approximately 60 % of the methanol decompose to surface intermediates CHxO (x = 2, 3) and 35 % to CHx (x = 1, 2), and an ultimate production of gaseous molecular hydrogen, methane, water and formaldehyde. The characteristic reactivity is attributed to both the triangular positioning and varied degrees of oxidation of the under-coordinated Pt at Te vacancies.

Nafion/Silver Nanoparticles as an Electrochemically Sensitive Interface for the Detection of Ractopamine in Pork Liver.

Many countries have allowed farmers to feed ß-adrenergic receptor agonists, such as ractopamine (Rac), to animals to improve the quality of their meat. However, Rac consumption can cause health problems for humans; thus, detecting Rac in meat before its packaging is essential. Consequently, this study developed a simple and sensitive electrochemical sensor by modifying a glassy carbon electrode (GCE) with Nafion/silver nanoparticles (Nafion/AgNPs). When this electrochemical sensor is used to detect Rac, electrostatic interaction occurs between Nafion and Rac, and the AgNPs oxidize Rac; thus, the accumulation and electrochemical sensing of Rac are achieved. Differential pulse voltammetry indicated that the as-prepared Nafion/AgNP-GCE sensor exhibited suitable electrochemical sensing ability under optimum conditions (6.0 µL of 0.10% Nafion/AgNPs in a Britton-Robertson buffer solution with a pH of 1.8, an accumulation potential of -0.2 V, and a Rac accumulation duration of 300 s). Moreover, this sensor has an extremely low limit of detection and high sensitivity (1.60 × 10-3 ppm and 2.14 µA/ppm, respectively) in the Rac concentration range 7.50 × 10-3-1.00 ppm. The as-prepared sensor also exhibits satisfactory reproducibility and storage stability, with the corresponding relative standard deviations (RSDs) being 4.27% (n = 5) and 1.56% (n = 10), respectively. The proposed electrochemical sensor was successfully used to determine the Rac content in pig liver samples, with spiked recoveries of 95.2-101.8% and RSDs of 0.55-4.83% being achieved.

Electron Injection via Interfacial Atomic Au Clusters Substantially Enhance the Visible-Light-Driven Photocatalytic H2 Production of the PF3T Enclosed TiO2 Nanocomposite.

A hybrid composite of organic-inorganic semiconductor nanomaterials with atomic Au clusters at the interface decoration (denoted as PF3T@Au-TiO2 ) is developed for visible-light-driven H2 production via direct water splitting. With a strong electron coupling between the terthiophene groups, Au atoms and the oxygen atoms at the heterogeneous interface, significant electron injection from the PF3T to TiO2 occurs leading to a quantum leap in the H2 production yield (18 578 µmol g-1 h-1 ) by ≈39% as compared to that of the composite without Au decoration (PF3T@TiO2 , 11 321 µmol g-1 h-1 ). Compared to the pure PF3T, such a result is 43-fold improved and is the best performance among all the existing hybrid materials in similar configurations. With robust process control via industrially applicable methods, it is anticipated that the findings and proposed methodologies can accelerate the development of high-performance eco-friendly photocatalytic hydrogen production technologies.

Experimental Revelation of Surface and Bulk Lattices in Faceted Cu2 O Crystals.

Semiconductor crystals have generally shown facet-dependent electrical, photocatalytic, and optical properties. These phenomena have been proposed to result from the presence of a surface layer with bond-level deviations. To provide experimental evidence of this structural feature, synchrotron X-ray sources are used to obtain X-ray diffraction (XRD) patterns of polyhedral cuprous oxide crystals. Cu2 O rhombic dodecahedra display two distinct cell constants from peak splitting. Peak disappearance during slow Cu2 O reduction to Cu with ammonia borane differentiates bulk and surface layer lattices. Cubes and octahedra also show two peak components, while diffraction peaks of cuboctahedra are comprised of three components. Temperature-varying lattice changes in the bulk and surface regions also show shape dependence. From transmission electron microscopy (TEM) images, slight plane spacing deviations in surface and inner crystal regions are measured. Image processing provides visualization of the surface layer with depths of about 1.5-4 nm giving dashed lattice points instead of dots from atomic position deviations. Close TEM examination reveals considerable variation in lattice spot size and shape for different particle morphologies, explaining why facet-dependent properties are emerged. Raman spectrum reflects the large bulk and surface lattice difference in rhombic dodecahedra. Surface lattice difference can change the particle bandgap.

Pt-Mediated Interface Engineering Boosts the Oxygen Reduction Reaction Performance of Ni Hydroxide-Supported Pd Nanoparticles.

Fuel cells are considered potential energy conversion devices for utopia; nevertheless, finding a highly efficacious and economical electrocatalyst for the oxygen reduction reaction (ORR) is of great interest. By keeping this in view, we have proposed a novel design of a trimetallic nanocatalyst (NC) comprising atomic Pt clusters at the heterogeneous Ni(OH)2-to-Pd interface (denoted NPP-70). The as-prepared material surpasses the commercial J.M.-Pt/C (20 wt %) catalyst by ∼ 166 and ∼19 times with exceptionally high specific and mass activities of 16.11 mA cm-2 and 484.8 mA mgPt-1 at 0.90 V versus reversible hydrogen electrode (RHE) in alkaline ORR (0.1 M KOH), respectively. On top of that, NPP-70 NC retains nearly 100% performance after 10k accelerated durability test (ADT) cycles. The results of physical characterization and electrochemical analysis confirm that atomic-scale Pt clusters induce strong lattice strain (compressive) at the Ni(OH)2-to-Pd interface, which triggers the electron relocation from Ni to Pt atoms. Such charge localization is vital for O2 splitting on surface Pt atoms, followed by the relocation of OH- ions from the Pd surface. Besides, a sharp fall down in ORR performance (mass activity is 37 mA mgPt-1 at 0.90 V versus RHE) is observed when the Pt clusters are decorated on the surface of NiOx and Pd (denoted NPP-RT). In situ partial fluorescence yield mode X-ray absorption spectroscopy (PFY-XAS) was employed to reveal the ORR pathways on both configurations. The obtained results demonstrate that interface engineering can be a potential approach to boost the electrocatalytic activity of metal hydroxide/oxide-supported Pd nanoparticles and in turn allow Pd to be a promising alternative for commercial Pt catalysts.

Toward Perfect Surfaces of Transition Metal Dichalcogenides with Ion Bombardment and Annealing Treatment.

Layered transition metal dichalcogenides (TMDs) are two-dimensional materials exhibiting a variety of unique features with great potential for electronic and optoelectronic applications. The performance of devices fabricated with mono or few-layer TMD materials, nevertheless, is significantly affected by surface defects in the TMD materials. Recent efforts have been focused on delicate control of growth conditions to reduce the defect density, whereas the preparation of a defect-free surface remains challenging. Here, we show a counterintuitive approach to decrease surface defects on layered TMDs: a two-step process including Ar ion bombardment and subsequent annealing. With this approach, the defects, mainly Te vacancies, on the as-cleaved PtTe2 and PdTe2 surfaces were decreased by more than 99%, giving a defect density <1.0 × 1010 cm-2, which cannot be achieved solely with annealing. We also attempt to propose a mechanism behind the processes.

Atomic Scaled Depth Correlation to the Oxygen Reduction Reaction Performance of Single Atom Ni Alloy to the NiO2 Supported Pd Nanocrystal.

This study demonstrates the intercalation of single-atom Ni (NiSA ) substantially reduces the reaction activity of Ni oxide supported Pd nanoparticle (NiO2 /Pd) in the oxygen reduction reaction (ORR). The results indicate the transition states kinetically consolidate the adsorption energy for the chemisorbed O and OH species on the ORR activity. Notably, the NiO2 /Ni1 /Pd performs the optimum ORR behavior with the lowest barrier of 0.49 eV and moderate second-step barrier of 0.30 eV consequently confirming its utmost ORR performance. Through the stepwise cross-level demonstrations, a structure-Eads -ΔE correspondence for the proposed NiO2 /Nin /Pd systems is established. Most importantly, such a correspondence reveals that the electronic structure of heterogeneous catalysts can be significantly differed by the segregation of atomic clusters in different dimensions and locations. Besides, the doping-depth effect exploration of the NiSA in the NiO2 /Pd structure intrinsically elucidates that the Ni atom doping in the subsurface induces the most fruitful NiSA /PdML synergy combining the electronic and strain effects to optimize the ORR, whereas this desired synergy diminishes at high Pd coverages. Overall, the results not only rationalize the variation in the redox properties but most importantly provides a precision evaluation of the process window for optimizing the configuration and composition of bimetallic catalysts in practical experiments.

Unveiling the hybridization between the Cr-impurity-mediated flat band and the Rashba-split state of the α-Au/Si(111) surface.

Adsorption of foreign atoms onto 2D materials can either lead to ordinary electron doping or the emergence of new electronic effects including topology, superconductivity, and quantum anomalous Hall and Kondo states. We have investigated the effect of Cr doping on the electronic structure of the α-Au/Si(111)- surface and its adsorbate-modified family. It has been found that below a critical coverage of ∼0.05 monolayer, Cr adatoms penetrate beneath the Au and topmost Si layers and induce the occupied resonance flat band in the electronic spectrum as revealed by angle-resolved photoelectron spectroscopy. Further deposition of Cr leads to the growth of the 3D islands spoiling the surface homogeneity. Using density functional theory calculations, we have disclosed the effects of Cr doping on the electronic band structure and revealed the nature of hybridization between the Cr-induced magnetic-split band and the Au-induced Rashba-split surface state. We believe that the synthesized 2D phases and electronic effects produced by magnetic atom doping in the ultimate two-dimensional limit will stimulate further investigations related to the highly correlated phases and will find practical applications in nanoelectronic devices.

Rubbing-free liquid crystal electro-optic device based on organic single-crystal rubrene.

Liquid crystals (LCs) have been a vital component of modern communication and photonic technologies. However, traditional LC alignment on polyimide (PI) requires mechanically rubbing treatment to control LC orientation, suffering from dust particles, surface damage, and electrostatic charges. In this paper, LC alignment on organic single-crystal rubrene (SCR) has been studied and used to fabricate rubbing-free LC devices. A rubrene/toluene solution is spin-coated on the indium-tin-oxide (ITO) substrate and transformed thereafter to the orthorhombic SCR after annealing. Experimental result reveals that SCR-based LC cell has a homogeneous alignment geometry, the pretilt angle of LCs is low and the orientation of LCs is determined with capillary filling action of LCs. LC alignment on SCR performs a wider thermal tolerance than that on PI by virtue of the strong anchoring nature of LCs on SCR due to van der Waals and π-π electron stacking interactions between the rubrene and LCs. SCR-based LC cell performs a lower operation voltage, faster response time, and higher voltage holding ratio than the traditional PI-based LC cell. Organic SCR enables to play a role as weakly conductive alignment layer without rubbing treatment and offers versatile function to develop novel LC devices.

Tri-atomic Pt clusters induce effective pathways in a Cocore-Pdshell nanocatalyst surface for a high-performance oxygen reduction reaction.

The crux of the hot topic concerning the widespread replacement of fuel cells (FCs) with traditional petrochemical energy is to balance improving the oxygen reduction reaction (ORR) and reducing the cost. The present study employs density functional theory (DFT) to investigate the effect of Pt ensemble size regulation from a single atom to full coverage on the physio-chemical properties, oxygen adsorption energies and overall ORR efficiency of bimetallic nanocatalysts (NCs) with a Cocore-Pdshell structure. Our results reveal that the electronegativity difference and lattice strain between neighboring heteroatoms are enhanced to trigger a synergetic effect in local domains, with the Pt cluster size reduced from nanometers to subnanometers. They induce a directed and tunable charge relocation mechanism from deep Co to topmost Pt to optimize the adsorption energies of O2/O* and achieve excellent ORR kinetics performance with minimum Pt usage but maximum Pt atom utilization (i.e., Pt1 to Pt3) compared with benchmark Pt(111). Such a dependency between the cluster size and corresponding ORR performance for the established Co@Pd-Ptn system can be applied to accurately guide the experimental synthesis of ordered heterogeneous catalysts (e.g., other core@shell-clusters structures) toward low Pt, high efficiency and green economy.

Achieving large uniform tensile elasticity in microfabricated diamond.

Diamond is not only the hardest material in nature, but is also an extreme electronic material with an ultrawide bandgap, exceptional carrier mobilities, and thermal conductivity. Straining diamond can push such extreme figures of merit for device applications. We microfabricated single-crystalline diamond bridge structures with ~1 micrometer length by ~100 nanometer width and achieved sample-wide uniform elastic strains under uniaxial tensile loading along the [100], [101], and [111] directions at room temperature. We also demonstrated deep elastic straining of diamond microbridge arrays. The ultralarge, highly controllable elastic strains can fundamentally change the bulk band structures of diamond, including a substantial calculated bandgap reduction as much as ~2 electron volts. Our demonstration highlights the immense application potential of deep elastic strain engineering for photonics, electronics, and quantum information technologies.

Collaboration between a Pt-dimer and neighboring Co-Pd atoms triggers efficient pathways for oxygen reduction reaction.

The development of electrocatalysts with reconcilable balance between the cost and performance in oxygen reduction reaction (ORR) is an imperative task for the widespread adoption of fuel cell technology. In this study, we proposed a unique model of diatomic Pt-cluster (Pt-dimer) in the topmost layer of the Co/Pd bimetallic slab (Co@Pd-Pt2) for mimicking the Cocore@Pdshell nanocatalysts (NCs) surface and systematically investigating its local-regional collaboration pathways in ORR by density functional theory (DFT). The results demonstrate that the Pt-dimer produces local differentiation from both ligand and geometric effects on the Co@Pd surface, which forms adsorption energy (Eads) gradients for relocating the ORR-adsorbates. Our calculations for Eads-variations of ORR-species, reaction coordinates, and intraparticle charge injection propose and confirm a novel local synergetic collaboration around the Pt-dimer in the Co@Pd-Pt2 system with the best-performing ORR behavior compared with all reference models. With proper selection of the composition in intraparticle components, the proposed DFT assessments could be adopted for developing economical and high-performance catalysts in various heterogeneous reactions.

Unravelling the Role of Structural Geometry and Chemical State of Well-Defined Oxygen Vacancies on Pristine CeO2 for H2O2 Activation.

Although H2O2 has been often employed as a green oxidant for many CeO2-catalyzed reactions, the underlying principle of its activation by surface oxygen vacancy (Vo) is still elusive due to the irreversible removal of postgenerated Vo by water (or H2O2). The metastable Vo (ms-Vo) naturally preserved on pristine CeO2 surfaces was adopted herein for an in-depth study of their interplay with H2O2. Their well-defined local structures and chemical states were found facet-dependent affecting both the adsorption and subsequent activation of H2O2. It is concluded that a strong adsorption of H2O2 on ms-Vo may not guarantee its subsequent activation. The ms-Vo can be only free for the next catalytic cycle when the electron density of surface Ce is high enough to reduce/break the O-O bond of adsorbed H2O2. This explains the 211.8 and 35.8 times enhancement in H2O2 reactivity when the CeO2 surface is changed from (111) and (110) to (100).

Nanoisozymes: The Origin behind Pristine CeO2 as Enzyme Mimetics.

It is known that the interplay between molecules and active sites on the topmost surface of a solid catalyst determines its activity in heterogeneous catalysis. The electron density of the active site is believed to affect both adsorption and activation of reactant molecules at the surface. Unfortunately, commercial X-ray photoelectron spectroscopy, which is often adopted for such characterization, is not sensitive enough to analyze the topmost surface of a catalyst. Most researchers fail to acknowledge this point during their catalytic correlation, leading to different interpretations in the literature in recent decades. Recent studies on pristine Cu2 O [Nat. Catal. 2019, 2, 889; Nat. Energy 2019, 4, 957] have clearly suggested that the electron density of surface Cu is facet dependent and plays a key role in CO2 reduction. Herein, it is shown that pristine CeO2 can reach 2506/1133 % increase in phosphatase-/peroxidase-like activity if the exposed surface is wisely selected. By using NMR spectroscopy with a surface probe, the electron density of the surface Ce (i.e., the active site) is found to be facet dependent and the key factor dictating their enzyme-mimicking activities. Most importantly, the surface area of the CeO2 morphologies is demonstrated to become a factor only if surface Ce can activate the adsorbed reactant molecules.

Molecular doping of blue phosphorene: a first-principles investigation.

Using first-principles calculations, we show that p-doped blue phosphorene can be obtained by molecular doping with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) and 1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F6-TNAP), whereas n-doped blue phosphorene can be realized by doping with tetrathiafulvalene (TTF) and cyclooctadecanonaene (CCO). Moreover, the doping gap can be effectively modulated in each case by applying an external perpendicular electric field. The optical absorption of blue phosphorene can be considerably enhanced in a broad spectral range through the adsorption of CCO, F4-TCNQ, and F6-TNAP molecules, suggesting potential of the doped materials in the field of renewable energy.

The influence of dilute aluminum and molybdenum on stacking fault and twin formation in FeNiCoCr-based high entropy alloys based on density functional theory.

Stacking faults, as defects of disordered crystallographic planes, are one of the most important slipping mechanisms in the commonly seen lattice, face-centered cubic (FCC). Such defects can initiate twinning which strengthens mechanical properties, e.g. twinning-induced plasticity (TWIP), of high entropy alloys (HEAs) at cryogenic temperatures. In this work, by using density functional theory (DFT), the twinning initiated from stacking faults is discussed with regard to two different solute elements, Al and Mo, in the FeNiCoCr HEAs. Our results show that adding aluminum (Al) has noticeable enhancement of twinnability while molybdenum (Mo) only induces more stacking faults in the FeNiCoCr-based HEAs.

Tunable Schottky barrier in graphene/graphene-like germanium carbide van der Waals heterostructure.

The structural and electronic properties of van der Waals (vdW) heterostructrue constructed by graphene and graphene-like germanium carbide were investigated by computations based on density functional theory with vdW correction. The results showed that the Dirac cone in graphene can be quite well-preserved in the vdW heterostructure. The graphene/graphene-like germanium carbide interface forms a p-type Schottky contact. The p-type Schottky barrier height decreases as the interlayer distance decreases and finally the contact transforms into a p-type Ohmic contact, suggesting that the Schottky barrier can be effectively tuned by changing the interlayer distance in the vdW heterostructure. In addition, it is also possible to modulate the Schottky barrier in the graphene/graphene-like germanium carbide vdW heterostructure by applying a perpendicular electric field. In particular, the positive electric field induces a p-type Ohmic contact, while the negative electric field results in the transition from a p-type to an n-type Schottky contact. Our results demonstrate that controlling the interlayer distance and applying a perpendicular electric field are two promising methods for tuning the electronic properties of the graphene/graphene-like germanium carbide vdW heterostructure, and they can yield dynamic switching among p-type Ohmic contact, p-type Schottky contact, and n-type Schottky contact in a single graphene-based nanoelectronics device.