Critical Descriptor Research Articles

Non-sacrificial anionic surfactant with high HOMO energy level as a general descriptor for zinc anode

Hydrogen evolution and dendrite growth severely plague the implementation of aqueous zinc-ion batteries. The electrolyte regulation strategy is powerful to alleviate the excrescent reactions of the electrolyte to Zn anode. However, there lacks effective electrolyte approaches for regulating stable and reversible Zn plating/stripping chemistry. Herein, we propose a general principle through evaluating the highest occupied molecular orbital (HOMO) energy level of molecules and employ it as a critical descriptor to select non-sacrificial anionic surfactant electrolyte additives for stabilizing Zn anodes. Benefiting from the high HOMO energy level, the excellent coordination and adsorption effects of the non-sacrificial surfactant additive renders the modulated solvation structure and dynamic molecule-enriched layer on the Zn anode, realizing sustainable regulation effect. The optimized electrolyte reduces water activity, uniforms Zn2+ flux, and stabilizes 3D ion diffusion near the anode/electrolyte interface, leading to the inhibited parasitic reactions and homogenous Zn nucleation and growth. Consequently, a stable and reversible Zn anode is obtained, represented by an ultralong cycling lifespan over 3200 h at 2 mA cm−2/2 mAh cm−2 and high coulombic efficiency of 99.75 %. This study provides a general guidance for screening optimal electrolyte additives for high-performance aqueous zinc-ion batteries.

Spin‐Regulated Fenton‐Like Catalysis for Nonradical Oxidation over Metal Oxide@Carbon Composites

AbstractThe spin state of the transition metal species (TMs) has been recognized as a critical descriptor in Fenton‐like catalysis. The raised spin state of dispersed TMs in carbon will enhance the redox processes with adsorbed peroxides and improve the oxidation performance. Nevertheless, establishing the spin‐activity correlations for the encapsulated TM nanoparticles remains challenging because of the difficulties in fine‐tuning the spin state of TM species and the insufficient understanding of orbital hybridization states upon interaction with peroxides. Here, the advantage of the fast‐temperature heating/quenching of microwave thermal shock is taken to engineer the structure and spin state of encapsulated TMs within the N‐doped graphitic carbons. The reduced TMs particle size and enhanced TMs‐carbon coupling increase surface entropy and regulate eg electron filling of the high‐spin TM‐N coordination, endowing electrons with high mobility and facilitating peroxymonosulfate (PMS) adsorption. The strong interactions further uplift the PMS O 2p band position toward the Fermi level and thus elevate the oxidation potential of surface‐activated PMS (PMS*) as the dominant nonradical species for pollutant degradation. The deciphered orbital hybridizations of engineered high‐spin TM and PMS enlighten the smart design of spin‐regulated nanocomposites for advanced water purification.

An effective descriptor for the screening of electrolyte additives toward the stabilization of Zn metal anodes

In this work, the authors proposed desolvation activation energy as a critical descriptor for the screening of electrolyte additives, establishing a correlation between polarization and desolvation activation energy.

Lewis acidity/basicity of inorganic interlayers as a descriptor for inhibition of charge shuttling in DMPZ-based organic batteries

A disadvantage of organic battery electrode materials is their solubility in battery electrolytes, leading to the shuttle effect. One solution is to use an additional separator, the interlayer, to inhibit charge shuttling of the solubilized species. The work here aims to identify the interlayer material's properties critical to reducing the shuttle effect so as to provide some guidance on interlayer material selection. Using various alumina as interlayer materials in batteries with N,N′-dimethylphenazine (DMPZ) as cathode material, surface charge can be identified as the critical descriptor to inhibiting DMPZ shuttling, more so than morphological properties. Specifically, the interlayer material can be selected for shuttling prevention in the same way as how one chooses chromatography stationary phase for analyte retention. Based on further characterizations, short- and long-term shuttling inhibition can be attributed to the interlayer and the solid-electrolyte interface formed in situ, respectively.

Maximizing Electrostatic Polarity of Non‐Sacrificial Electrolyte Additives Enables Stable Zinc‐Metal Anodes for Aqueous Batteries

AbstractAlthough additives are widely used in aqueous electrolytes to inhibit the formation of dendrites and hydrogen evolution reactions on Zn anodes, there is a lack of rational design principles and systematic mechanistic studies on how to select a suitable additive to regulate reversible Zn plating/stripping chemistry. Here, using saccharides as the representatives, we reveal that the electrostatic polarity of non‐sacrificial additives is a critical descriptor for their ability to stabilize Zn anodes. Non‐sacrificial additives are found to continuously modulate the solvation structure of Zn ions and form a molecular adsorption layer (MAL) for uniform Zn deposition, avoiding the thick solid electrolyte interphase layer due to the decomposition of sacrificial additives. A high electrostatic polarity renders sucrose the best hydrated Zn2+ desolvation ability and facilitates the MAL formation, resulting in the best cycling stability with a long‐term reversible plating/stripping cycle life of thousands of hours. This study provides theoretical guidance for the screening of optimal additives for high‐performance ZIBs.

Maximizing Electrostatic Polarity of Non-Sacrificial Electrolyte Additives Enables Stable Zinc-Metal Anodes for Aqueous Batteries.

Although additives are widely used in aqueous electrolytes to inhibit the formation of dendrites and hydrogen evolution reactions on Zn anodes, there is a lack of rational design principles and systematic mechanistic studies on how to select a suitable additive to regulate reversible Zn plating/stripping chemistry. Here, using saccharides as the representatives, we reveal that the electrostatic polarity of non-sacrificial additives is a critical descriptor for their ability to stabilize Zn anodes. Non-sacrificial additives are found to continuously modulate the solvation structure of Zn ions and form a molecular adsorption layer (MAL) for uniform Zn deposition, avoiding the thick solid electrolyte interphase layer due to the decomposition of sacrificial additives. A high electrostatic polarity renders sucrose the best hydrated Zn2+ desolvation ability and facilitates the MAL formation, resulting in the best cycling stability with a long-term reversible plating/stripping cycle life of thousands of hours. This study provides theoretical guidance for the screening of optimal additives for high-performance ZIBs.

Unveiling the role of hydroxyl groups in glycerol as a critical descriptor for efficient electrocatalytic reforming of biomass molecules using PtCu alloy nanoparticle catalysts

Glycerol, one of the main byproducts of biodiesel production, has recently attracted attention since it can co-generate electricity and valuable chemicals via electrochemical glycerol oxidation reaction (EGOR). Due to the complexity of EGOR, there have been many arguments about its pathways to find the environmental conditions for producing targeted chemicals. The studies to find the representative descriptor that affects EGOR were performed, using a combination of ab-initio computational and experimental approaches. A novel porous carbon (PC) was employed as an effective support material to synthesize PtCu/PC catalysts, and then various electrochemical analyses were carried out. The adsorption energies of hydroxide and the binding strength of the hydroxyl groups in the glycerol on the catalysts were compared using a crystal orbital Hamilton population (COHP) analysis. Consequently, we found the tendency in the binding strength of hydroxyl group as a critical descriptor, rationalizing why the PtCu3/PC catalyst revealed the highest mass activity for EGOR.

Are formation and adsorption energies enough to evaluate the stability of surface-passivated tin-based halide perovskites?

Surface passivation is one of the effective and widely-used strategies to enhance the stability of halide perovskites with reduced surface defects and suppressed hysteresis. Among all existing reports, the formation and adsorption energies are popularly used as the decisive descriptors for screening passivators. Here, we propose that the often-ignored local surface structure should be another critically important factor governing the stability of tin-based perovskites after surface passivation, but has no detrimental effect on the stability of lead-based perovskites. It is verified that poor surface structure stability and deformation of the chemical bonding framework of Sn-I caused by surface passivation are ascribed to the weakened Sn-I bond strength and facilitated formation of surface iodine vacancy (VI). Therefore, the surface structure stability represented by the formation energy of VI and Sn-I bond strength should be used to accurately screen preferred surface passivators of tin-based perovskites.

Knowledge of genetic test results among caregivers and individuals with spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a progressive recessive genetic disease. Early identification is critical for achieving maximal treatment benefit. Survival motor neuron (SMN) 2 copy number may be a needed descriptor of disease severity than SMA type. Therefore, we assessed knowledge of SMN2 copy number among those with SMA and their caregivers via a phone survey. Only patients with SMA (or their caregivers) registered in the Cure SMA database with no SMN2 copy number on file were eligible. Descriptive results are reported. Backward stepwise multinomial logistic regressions determined if specific factors predicted knowledge of SMN2 copy number. Engagement with the SMA community (odds ratio [OR] 1.82; p<0.0001), ability to walk (OR 1.74; p = 0.006), and current age at time of survey (OR = 0.98; p<0.0001) each positively predicted knowledge of SMN2 copy number. Of 806 completed surveys, the majority (n = 452; 56.3%) did not know SMN2 copy numbers for themselves (n = 190; 62.5%) or their loved ones (n = 261; 52.4%). Of these, 66 respondents (8.2%) said genetic testing had not been done. Motor function increased linearly with increasing SMN2 copy number. SMN2 copy number is emerging as a critical descriptor of severity for SMA as type becomes more obsolete with early drug treatment. Communication of SMN2 copy numbers is recommended as a standard part of the treatment plan.

Rethinking the Design of Ionic Conductors Using Meyer–Neldel–Conductivity Plot

AbstractFrom the discovery of the first fast ionic conductor silver iodide in the early 20th century to the recent discovery of lithium fast ionic conductors with ionic conductivities surpassing those of liquid electrolytes, high ionic conductivity σ has often been associated with low activation energy Ea following the Arrhenius equation. However, the Meyer–Neldel rule (MNR) indicates that the Ea and prefactor σ0 are correlated, suggesting the relation between the Ea and σ is, in fact, complex. In this perspective, the use of the Meyer–Neldel–conductivity plot and a critical descriptor, Meyer–Neldel energy Δ0, to guide the search for fast ionic conductors is proposed. Reported lithium, sodium, and magnesium ionic conductors are categorized into three types, depending on the relative magnitude between the Δ0 and thermal energy (kBT) at the application temperature. The process by which σ can be optimized by tuning Ea for these types of ionic conductors is elaborated. This principle can be widely applied to all ionic conductors that obey the MNR at any application temperature. Furthermore, a pressure‐tuning approach to measure the Δ0 rapidly is developed. These findings establish a previously missing step for designing new ionic conductors with improved ionic conductivity.

The prediction of the turned machining induced residual stresses in Ti6Al4V: A Critical Surface Integrity Descriptor

The surface integrity of a turned machined surface is an essential indicator of the fatigue and corrosion performance of a component. A critical descriptor of this property is the residual stress, both on the surface and subsurface of a part. However, experimental determination of vital surface integrity parameters such as surface roughness, hardness, affected microstructure, and residual stresses is costly, time consuming, and involves the destruction of the part. Therefore, prediction of these parameters, such as residual stress versus depth, would be of great value and could aid in the correct machining parameters (cutting speed, feed rate, edge tool radius, rake angle, coolant) for the desired part performance. A study was initiated to determine the influence of a worn tool and multiple cuts on a wide range of cutting speeds on residual stresses induced by machining an outside-turned bar of Ti6Al4V titanium alloy. Thus, a project was initiated to develop a non-linear finite element model to predict the residual stresses thus developed due to the machining manufacturing process.

Voltammetric pH Measurements in Unadulterated Foodstuffs, Urine, and Serum with 3D-Printed Graphene/Poly(Lactic Acid) Electrodes.

The pH of a system is a critical descriptor of its chemistry-impacting reaction rates, solubility, chemical speciation, and homeostasis. As a result, pH is one of the most commonly measured parameters in food safety, clinical, and environmental laboratories. Glass pH probes are the gold standard for pH measurements but suffer drawbacks including frequent recalibration, wet storage of the glass membrane, difficulty in miniaturization, and interferences from alkali metals. In this work, we describe a voltammetric pH sensor that uses a three-dimensional (3D)-printed graphene/poly(lactic acid) filament electrode that is pretreated to introduce quinone functional groups to the graphene surface. After thoroughly characterizing the pretreatment parameters using outer-sphere and inner-sphere redox couples, we measured pH by reducing the surface-bound quinones, which undergo a pH-dependent 2e-/2H+ reduction. The position of the redox peak was found to shift -60 ± 2 mV pH-1 at 25 °C, which is in excellent agreement with the theoretical value predicted by the Nernst Equation (-59.2 mV pH-1). Importantly, the sensors did not require the removal of dissolved oxygen prior to successful pH measurements. We investigated the impact of common interfering species (Pb2+ and Cu2+) and found that there was no impact on the measured pH. We subsequently challenged the sensors to measure the pH of unadulterated complex samples, including cola, vinegar, an antacid tablet slurry, serum, and urine, and obtained excellent agreement compared to a glass pH electrode. In addition to the positive analytical characteristics, the sensors are extremely cheap and easy to fabricate, making them highly accessible to a wide range of researchers. These results pave the way for customizable pH sensors that can be fabricated in (nearly) any geometry for targeted applications using 3D printing.

A picture of pseudogap phase related to charge fluxes

Recently, charge density fluctuations or charge fluxes attract strong interests in understanding the unconventional superconductivity. In this paper, a new emergent configuration in cuprates is identified by density functional theory simulations, called the charge pseudoplane, which exhibits the property of confining the dynamic charge fluxes for higher superconducting transition temperatures. It further redefines the fundamental collective excitation in cuprates as pQon with the momentum-dependent and ultrafast localization-delocalization duality. It is shown that both pseudogap and superconducting phases can be born from and intertwined through the charge flux confinement property of the charge pseudoplane region. Our experimental simulations based on the new picture provide good agreements with previous angle resolved photoemission spectroscopy and scanning tunneling microscopy results. Our work thus opens a new perspective into the origin of the pseudogap phase and other related phases in cuprates, and further provides a critical descriptor to search and design higher temperature superconductors.

Allometric scaling of Lyapunov exponents in chaotic populations

AbstractChaos has been a central topic of research in ecology for decades, in part because of its implications for the predictability of population dynamics. Chaotic systems are characterized by low predictability at long timescales, as slight differences in initial conditions (e.g., the actual vs. the measured initial conditions) yield trajectories (e.g., the actual vs. the predicted trajectory) that diverge exponentially at a rate determined by the global Lyapunov Exponent (LE). The LE is therefore a critical descriptor of chaotic systems that sets the time horizon for predictability. Recent observations of chaos in populations or communities have shown that LEs vary by at least two orders of magnitude, yet the factors underlying this variability remain unclear. Here, we examine the drivers of heterogeneity in LEs among chaotic populations and communities. We show that LEs decline with increasing body size as a shallow power law (exponent −0.21), suggesting that LEs are inversely proportional to the populations' generation time (GT). However, this allometric scaling relationship holds only when considering the larger, slower growing populations in multispecies communities (the primary and secondary consumers), indicating that these populations constrain or determine LEs for the community. These results suggest that the rate at which the predictability of a chaotic time series declines over time generally reflects either the populations' GT, or that of a slower growing population in the community.

Designing Flexible Quantum Spin Hall Insulators through 2D Ordered Hybrid Transition-Metal Carbides

Quantum spin Hall (QSH) insulators have attracted much attention due to their potential applications ranging from electronic devices to quantum computing. In general, a large band gap is regarded as a critical descriptor in the design of QSH insulators; however, it faces challenges when additional factors such as strain and surface oxidation are involved in practical applications. In this work, taking M″2M′C2O2 (M′ = Ti, Zr, Hf; M″ = Mo, W) as a representative, results reveal that 2D ordered transition-metal carbides (MXenes) are promising candidates for flexible spintronic devices, which is ascribed to the mechanical flexibility and robust QSH states under strain. Although a large bulk band gap is shown in M″2HfC2O2, a strain-induced topological phase transition may limit its flexible application. On the contrary, M″2TiC2O2 has a smaller gap, and its topological nontrivial state survives under strain. When n changes from 0 to 4 in M″2TinCn+1O2, a topologically nontrivial–trivial phase transition is obser...

Surface Modulation of PdCu Nanocatalysts Via the Crystal Structure Change for Lithium-Oxygen Battereis

Palladium-copper (PdCu) alloys have two representative crystal structures; one is body-centered cubic (bcc), the other is face-centered cubic (fcc) even though both Pd and Cu originally have fcc crystal. The fcc PdCu alloys have disordered structure within which Pd and Cu have solid-solution in fcc lattice, whereas the bcc PdCu alloys have ordered structure which consists of alternative layers with either Pd or Cu atoms. In particular, bcc PdCu alloys have occasionally shown superior performance to fcc PdCu alloys since the unique ordered structure of bcc has isolated Pd on the surface. Most of bcc PdCu alloys have been synthesized for structural transformation by annealing or seed-growth method of fcc PdCu alloys with inevitable grain growth, uneven surface structure and particle size distribution. Despite these limitations, the Pd on the bcc surface which is provided charge flow from Cu serves as an active site for catalytic reaction, which is highly favorable for lithium-oxygen battery. However, the same size of fcc and bcc PdCu alloys is quite difficult to be obtained since the crystallites larger than 20 nm favor the ordered bcc structure with lower symmetry. Thus, bcc PdCu alloys in nanoscale have been rarely reported, consequently fcc and bcc PdCu nanoparticles (NPs) have never been properly compared until now. In this study, we successfully synthesize fcc and bcc PdCu alloys in nanoscale through precisely adjusting the driving force for reducing organometallic complex. The bcc PdCu NPs with higher surface energy govern the growth thermodynamics of discharge product and greatly improved battery performance based on density functional theory calculation and experimental proof. This study provides critical descriptor on material design in the perspective of modulating surface structure via crystal structure to tune its intrinsic properties.

Anisotropic Surface Modulation of Pt Catalysts for Highly Reversible Li–O2 Batteries: High Index Facet as a Critical Descriptor

The surface structure of solid catalysts has been regarded as a critical descriptor for determining the catalytic activities in various applications. However, structure-dependent catalytic activities have been rarely understood for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) within Li-O2 batteries. Here, we succeeded in the preparation of a Pt catalyst with an anisotropic structure and demonstrated its high catalytic activity in non-aqueous Li-O2 batteries. The cathode incorporating Pt exposed with high-index {411} facets showed greatly enhanced ORR and OER performance in comparison to commercial Pt/C cathode. The anisotropic Pt catalyst improved ORR activity with a large capacity of 12,985 mAh gcarbon-1, high rate performance, and stable cyclic retention up to 70 cycles with the capacity limited to 1,000 mAh gcarbon-1 of capacity. Furthermore, the anisotropic Pt catalyst exhibited high round-trip efficiency of ~87% with a low OER potential (3.1 V) at a current density of 200 m...

Surface Energy Modulation of PdCu Nanocatalysts Via the Crystal Structure Change for Lithium-Oxygen Battereis

Palladium-copper (PdCu) alloys have two representative crystal structures; one is body-centered cubic (bcc), the other is face-centered cubic (fcc) even though both Pd and Cu originally have fcc crystal. The fcc PdCu alloys have disordered structure within which Pd and Cu have solid-solution in fcc lattice, whereas the bcc PdCu alloys have ordered structure which consists of alternative layers with either Pd or Cu atoms. In particular, bcc PdCu alloys have occasionally shown superior performance to fcc PdCu alloys since the unique ordered structure of bcc has isolated Pd on the surface. Most of bcc PdCu alloys have been synthesized for structural transformation by annealing or seed-growth method of fcc PdCu alloys with inevitable grain growth, uneven surface structure and particle size distribution. Despite these limitations, the Pd on the bcc surface which is provided charge flow from Cu serves as an active site for catalytic reaction, which is highly favorable for lithium-oxygen battery. However, the same size of fcc and bcc PdCu alloys is quite difficult to be obtained since the crystallites larger than 20 nm favor the ordered bcc structure with lower symmetry. Thus, bcc PdCu alloys in nanoscale have been rarely reported, consequently fcc and bcc PdCu nanoparticles (NPs) have never been properly compared until now. In this study, we successfully synthesize fcc and bcc PdCu alloys in nanoscale through precisely adjusting the driving force for reducing organometallic complex. The bcc PdCu NPs with higher surface energy govern the growth thermodynamics of discharge product and greatly improved battery performance based on density functional theory calculation and experimental proof. This study provides critical descriptor on material design in the perspective of modulating surface structure via crystal structure to tune its intrinsic properties.

Critical Descriptor for the Rational Design of Oxide-Based Catalysts in Rechargeable Li–O2Batteries: Surface Oxygen Density

Li–O2 batteries provide high-capacity energy storage, but for aprotic Li–O2 batteries, it is reported that the charge–discharge efficiency is ultimately limited by the crystal growth of insoluble Li2O2 on the porous cathode. Catalysts have been reported to improve the nucleation and morphology of Li2O2, which helps achieve high energy densities. We provide a new insight into the catalytic mechanism of the oxygen reduction reaction (ORR) in aprotic Li–O2 batteries—the oxygen sites on the surface play a more important role than the exposed metal sites—via a study based on the density functional theory (DFT) examining α-MnO2 surfaces. Lithium ions from electrolytes are found to interact with the surface oxygen sites and form surface lithium sites, facilitating further growth of Li2O2. A larger number of initial growth points with uniform distribution makes Li2O2 well dispersed, forming small particles, which benefit both the ORR and oxygen evolution reactions (OER). This design concept for oxygen sites has b...

Selection on adult female body size in rhesus macaques

Body size is a critical descriptor of animal biology with many ecological, behavioral, and physiological correlates. Size differences among species or between populations are often explained by adaptive scenarios invoking the action of selection, although studies of selection in action on primate body size, or other phenotypic traits, are very rare. We document directional selection for larger skull and postcranial size in the skeletons of female semi-free ranging rhesus macaques ( Macaca mulatta) from Cayo Santiago, born between 1957 and 1982. Larger females live to later ages and consequently give birth to more offspring. Despite selection for larger size, there are indications of a trend toward generally smaller size in the same birth cohorts. This trend is provisionally attributed to increasing population density, though other environmental factors may play a role. Small selection differentials and low heritabilities also limit the genetic response to selection. Alternative explanations for increasing adult size in the skull and postcranium, such as continued adult growth or pathological bone deposition, do not adequately explain the observed age-related trends and are inconsistent with longitudinal studies of adult skeletal change.