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The sulfur reduction reaction (SRR) plays a central role in high-capacity lithium sulfur (Li-S) batteries. The SRR involves an intricate, 16-electron conversion process featuring multiple lithium polysulfide intermediates and reaction branches 1 – 3 . Establishing the complex reaction network is essential for rational tailoring of the SRR for improved Li-S batteries, but represents a daunting challenge 4 – 6 . Herein we systematically investigate the electrocatalytic SRR to decipher its network using the nitrogen, sulfur, dual-doped holey graphene framework as a model electrode to understand the role of electrocatalysts in acceleration of conversion kinetics. Combining cyclic voltammetry, in situ Raman spectroscopy and density functional theory calculations, we identify and directly profile the key intermediates (S 8 , Li 2 S 8 , Li 2 S 6 , Li 2 S 4 and Li 2 S) at varying potentials and elucidate their conversion pathways. Li 2 S 4 and Li 2 S 6 were predominantly observed, in which Li 2 S 4 represents the key electrochemical intermediate dictating the overall SRR kinetics. Li 2 S 6 , generated (consumed) through a comproportionation (disproportionation) reaction, does not directly participate in electrochemical reactions but significantly contributes to the polysulfide shuttling process. We found that the nitrogen, sulfur dual-doped holey graphene framework catalyst could help accelerate polysulfide conversion kinetics, leading to faster depletion of soluble lithium polysulfides at higher potential and hence mitigating the polysulfide shuttling effect and boosting output potential. These results highlight the electrocatalytic approach as a promising strategy for tackling the fundamental challenges regarding Li-S batteries. We investigate the mechanism underlying the sulfur reduction reaction that plays a central role in high-capacity lithium sulfur batteries, highlighting the electrocatalytic approach as a promising strategy for tackling the fundamental challenges associated with these batteries.

One of the long-standing challenges in experimental physics is the observation of room-temperature superconductivity . Recently, high-temperature conventional superconductivity in hydrogen-rich materials has been reported in several systems under high pressure . An  important discovery leading to room-temperature superconductivity is the pressure-driven disproportionation of hydrogen sulfide (H S) to H S, with a confirmed transition temperature of 203 kelvin at 155 gigapascals . Both H S and CH readily mix with hydrogen to form guest-host structures at lower pressures , and are of  comparable size at 4 gigapascals. By introducing methane at low pressures into the H S + H precursor mixture for H S, molecular exchange is allowed within a large assemblage of van der Waals solids that are hydrogen-rich with H inclusions; these guest-host structures become the building blocks of superconducting compounds at extreme conditions. Here we report superconductivity in a photochemically transformed carbonaceous sulfur hydride system, starting from elemental precursors, with a maximum superconducting transition temperature of 287.7 ± 1.2 kelvin (about 15 degrees Celsius) achieved at 267 ± 10 gigapascals. The superconducting state is observed over a broad pressure range in the diamond anvil cell, from 140 to 275 gigapascals, with a sharp upturn in transition temperature above 220 gigapascals. Superconductivity is established by the observation of zero resistance, a magnetic susceptibility of up to 190 gigapascals, and reduction of the transition temperature under an external magnetic field of up to 9 tesla, with an upper critical magnetic field of about 62 tesla according to the Ginzburg-Landau model at zero temperature. The light, quantum nature of hydrogen limits the structural and stoichiometric determination of the system by X-ray scattering techniques, but Raman spectroscopy is used to probe the chemical and structural transformations before metallization. The introduction of chemical tuning within our ternary system could enable the preservation of the properties of room-temperature superconductivity at lower pressures.

Zr2Fe alloy is a promising candidate as a tritium‐getter material for the International Thermonuclear Experimental Reactor (ITER), but its practical application is hindered by undesirable inverse disproportionation behavior and poor anti‐disproportionation properties. In this study, theoretical computational screening is utilized to predict the effects of partially substituting Fe with Co, Cu, and Ni on regulating the Zr2Fe1‐xMx (M = Co, Cu, Ni; x = 0.1–0.5) hydrogen storage systems. Experimentally, these modifications successfully correct the distorted inverse disproportionation reaction and achieve full reversibility in the Zr2Fe1‐xMx‐H systems. Notably, Zr2Fe0.8Cu0.2 and Zr2Fe0.7Ni0.3 alloys retain excellent hydrogen storage properties, while their kinetic energy barriers of hydriding disproportionation reaction increase significantly from 87.88 kJ mol−1 (Zr2Fe) to 184.35 kJ mol−1 (Zr2Fe0.8Cu0.2) and 192.32 kJ mol−1 (Zr2Fe0.7Ni0.3), respectively. The corresponding deceleration of hydriding disproportionation kinetics behaviors is clearly visualized by TEM observations. Combined density functional theory analyses reveal that the mechanism underlying enhanced anti‐disproportionation properties in the optimized Zr2Fe1‐xMx‐H systems involves the homogenization and stabilization of Zr─H bonds within the hydrogen storage interstices, along with the effective suppression of disproportionation‐favorable chemical environments. Undesirable phase transition behavior and anti‐disproportionation performance limit the hydrogen isotope storage of Zr2Fe alloy. With theoretical screening and experiments, partial Cu/Ni substitutions achieve full reversibility and significantly improve anti‐disproportionation properties. Modulation of charge redistribution and chemical environment, combined with thermodynamic suppression, synergistically enhance resistance to disproportionation.

Electroluminescence efficiencies and stabilities of quasi-two-dimensional halide perovskites are restricted by the formation of multiple-quantum-well structures with broad and uncontrollable phase distributions. Here, we report a ligand design strategy to substantially suppress diffusion-limited phase disproportionation, thereby enabling better phase control. We demonstrate that extending the π-conjugation length and increasing the cross-sectional area of the ligand enables perovskite thin films with dramatically suppressed ion transport, narrowed phase distributions, reduced defect densities, and enhanced radiative recombination efficiencies. Consequently, we achieved efficient and stable deep-red light-emitting diodes with a peak external quantum efficiency of 26.3% (average 22.9% among 70 devices and cross-checked) and a half-life of ~220 and 2.8 h under a constant current density of 0.1 and 12 mA/cm 2 , respectively. Our devices also exhibit wide wavelength tunability and improved spectral and phase stability compared with existing perovskite light-emitting diodes. These discoveries provide critical insights into the molecular design and crystallization kinetics of low-dimensional perovskite semiconductors for light-emitting devices. Quasi-2D halide perovskites are attracting increasing attention for light-emitting devices. Here, the authors demonstrated efficient and stable quasi-2D perovskite LEDs enabled by suppressed phase disproportionation with newly designed organic ligands.

Historically long accepted to be the singular root cause of capacity fading, transition metal dissolution has been reported to severely degrade the anode. However, its impact on the cathode behavior remains poorly understood. Here we show the correlation between capacity fading and phase/surface stability of an LiMn 2 O 4 cathode. It is revealed that a combination of structural transformation and transition metal dissolution dominates the cathode capacity fading. LiMn 2 O 4 exhibits irreversible phase transitions driven by manganese(III) disproportionation and Jahn-Teller distortion, which in conjunction with particle cracks results in serious manganese dissolution. Meanwhile, fast manganese dissolution in turn triggers irreversible structural evolution, and as such, forms a detrimental cycle constantly consuming active cathode components. Furthermore, lithium-rich LiMn 2 O 4 with lithium/manganese disorder and surface reconstruction could effectively suppress the irreversible phase transition and manganese dissolution. These findings close the loop of understanding capacity fading mechanisms and allow for development of longer life batteries. To unlock the potential of Mn-based cathode materials, the fast capacity fading process has to be first understood. Here the authors utilize advanced characterization techniques to look at a spinel LiMn 2 O 4 system, revealing that a combination of irreversible structural transformations and Mn dissolution takes responsibility.

With their broad range of properties, ABO 3 transition metal perovskite oxides have long served as a platform for device applications and as a testing bed for different condensed matter theories. Their insulating character and structural distortions are often ascribed to dynamical electronic correlations within a universal, symmetry-conserving paradigm. This view restricts predictive theory to complex computational schemes, going beyond density functional theory (DFT). Here, we show that, if one allows symmetry-breaking energy-lowering crystal symmetry reductions and electronic instabilities within DFT, one successfully and systematically recovers the trends in the observed band gaps, magnetic moments, type of magnetic and crystallographic ground state, bond disproportionation and ligand hole effects, Mott vs. charge transfer insulator behaviors, and the amplitude of structural deformation modes including Jahn-Teller in low temperature spin-ordered and high temperature disordered paramagnetic phases. We then provide a classification of the four mechanisms of gap formation and establish DFT as a reliable base platform to study the ground state properties in complex oxides. It is often stated that first principles studies of transition metal oxides require dynamically correlated methods to correctly produce gap formation, magnetism and structural distortions. Varignon et al. show instead that static correlations are sufficient to capture these features in the ABO 3 oxide series.

This article investigates the connection between the process parameters of solid hydrogenation, disproportionation (HD), desorption, and recombination (DR) (HDDR) in sintered (Nd,Pr,Gd)-Fe-B magnets, as well as their phase composition and degree of texture (DoT). During HD, hydrogen pressures of 10–50 kPa were applied at temperatures ranging from 700 to 785 °C for reaction times ranging from 3 to 11 h. DR was performed at 750–850 °C. The HD reaction was observed across the full range of hydrogen pressure and temperature. The phase composition of the disproportionation products depends on the depth in the sample. Applying HDDR treatment at a pressure of 10 kPa is an effective way to increase the DoT of magnets. Magnets are anisotropic following the HDDR treatment across the parameter ranges. The dependence of the DoT value on HDDR treatment parameters is complicated, with the main trend being a decline in DoT with increasing hydrogen pressure. The DoT is determined by the disproportionation and recombination temperatures, as well as the depth at 50 kPa pressure. The recombined phase is isotropic near the sample surface and highly anisotropic within the sample after 50 kPa is applied.

Realizing an efficient turnover frequency in the acidic oxygen evolution reaction by modifying the reaction configuration is crucial in designing high-performance single-atom catalysts. Here, we report a “single atom–double site” concept, which involves an activatable inert manganese atom redox chemistry in a single-atom Ru-Mn dual-site platform with tunnel Ni ions as the trigger. In contrast to conventional single-atom catalysts, the proposed configuration allows direct intramolecular oxygen coupling driven by the Ni ions intercalation effect, bypassing the secondary deprotonation step instead of the kinetically sluggish adsorbate evolution mechanism. The strong bonding of Ni ions activates the inert manganese terminal groups and inhibits the cross-site disproportionation process inherent in the Mn scaffolding, which is crucial to ensure the dual-site platform. As a result, the single-atom Ru-Ni-Mn octahedral molecular sieves catalyst delivers a low overpotential, adequate mass activity and good stability. Realizing an efficient turnover frequency by modifying the reaction configuration is crucial in designing single-atom catalysts. Here, authors report a “single atom–double site” concept, which involves activating inert atom redox chemistry.

Although Li–air rechargeable batteries offer higher energy densities than lithium-ion batteries, the insulating Li2O2 formed during discharge hinders rapid, efficient re-charging. Redox mediators are used to facilitate Li2O2 oxidation; however, fast kinetics at a low charging voltage are necessary for practical applications and are yet to be achieved. We investigate the mechanism of Li2O2 oxidation by redox mediators. The rate-limiting step is the outer-sphere one-electron oxidation of Li2O2 to LiO2, which follows Marcus theory. The second step is dominated by LiO2 disproportionation, forming mostly triplet-state O2. The yield of singlet-state O2 depends on the redox potential of the mediator in a way that does not correlate with electrolyte degradation, in contrast to earlier views. Our mechanistic understanding explains why current low-voltage mediators (<+3.3 V) fail to deliver high rates (the maximum rate is at +3.74 V) and suggests important mediator design strategies to deliver sufficiently high rates for fast charging at potentials closer to the thermodynamic potential of Li2O2 oxidation (+2.96 V).Ultra-high-capacity Li–air batteries have low Coulombic efficiency and degrade during re-charging, resulting in a poor cycle life. Redox mediators enable improvements but only at undesirably high potentials. The origin of this high potential and the impact of purported reactive intermediates has now been elucidated by resolving the charging mechanism using Marcus theory.

Electrodepositing insulating lithium peroxide (Li₂O₂) is the key process during discharge of aprotic Li–O₂ batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved lithium superoxide governs whether Li₂O₂ grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, better understanding governing factors for Li₂O₂ packing density and capacity requires structural sensitive in situ metrologies. Here, we establish in situ small- and wide-angle X-ray scattering (SAXS/WAXS) as a suitable method to record the Li₂O₂ phase evolution with atomic to submicrometer resolution during cycling a custom-built in situ Li–O₂ cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multiphase systems. Surprisingly, we find that features are absent that would point at a Li₂O₂ surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li₂O₂ platelets potentially forming large toroidal particles. Li₂O₂ solution growth is further justified by rotating ring-disk electrode measurements and electron microscopy. Higher discharge overpotentials lead to smaller Li₂O₂ particles, but there is no transition to an electronically passivating, conformal Li₂O₂ coating. Hence, mass transport of reactive species rather than electronic transport through a Li₂O₂ film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in weakly solvating electrolytes. The currently accepted Li–O₂ reaction mechanism ought to be reconsidered.