Search

Resource‐rich FeS2 is a promising anode for potassium‐ion batteries (PIBs). However, polysulfides emerge due to FeS2 conversion during discharging, which dissolve into the ether‐based electrolyte and cause the continuous capacity degradation in PIBs. To address the polysulfides dissolution in PIBs, a graphene–shell‐encapsulated FeS2 is fabricated and embedded in N/S codoped 3D hollow carbon spheres. As a protective pocket, the graphene–shell can effectively accommodate polysulfides inside the core–shell, inhibiting the polysulfides shuttle effect to enhance cycle stability of electrode. The density functional theory (DFT) calculations demonstrate that graphene–shells have a strong adsorption capacity for polysulfides, and the interfacial interaction between KFeS2 and graphene–shell can boost the K ion mobility. As a result, the composite exhibits superior‐rate properties (524 and 224 mA h g−1 at 0.1 and 8 A g−1, respectively) and long‐term cycle stability. This work demonstrates the promotion and protective effect of the graphene–shell for the FeS2 to storage K from both experimental and computational perspectives. These research outputs can provide guidance for designing other metal‐based sulfide electrodes for PIBs. [ABSTRACT FROM AUTHOR]

The magnetoelectric multiferroic materials with ferroelectric and magnetic orders have great attributed attention in the field of magnetoelectric memories and magnetic resonance devices. Here, we systematically investigated the optical and multiferroic properties of Fe-doped hybrid improper ferroelectricity Ca 3 Ti 2 O 7 prepared by sol-gel method. The distortion of TiO 6 octahedron changes with the content of oxygen vacancy introduced by Fe doping, thus realizing the adjustment of remnant ferroelectric polarization of the samples. The slight blue shift of the Raman band at 667 cm−1 reflected the introduces of oxygen vacancies by Fe doping. The optical bandgaps of the doped samples were reduced after doping, agreeing with the results of the first-principles calculations. With the introduction of Fe3+, the magnetism increases gradually. The first-principles calculation shows that magnetism origins from the Fe-3 d and their surrounding O-2 p orbitals. The Fe-doping Ca 3 Ti 2 O 7 materials realizing the introduction of magnetic properties while regulating its ferroelectric properties are expected to be applied in magnetoelectric memories, optoelectronic devices spintronics and magnetic response devices. [Display omitted] • The Fe-doped Ca 3 Ti 2 O 7 prepared with sol-gel possesses shows low coercivity field and large ferroelectric polarization. • The magnetism increases due to the introduces of Fe3+ in the doped samples, which is attributed to the spin splitting of Fe-3 d and their surrounding O atoms analyzed though first-principles calculations. • The slight blue shift of the Raman band upon Fe doping is attributed to the introduce oxygen vacancies, which also leads to a decrease of the bandgaps. • The O atom has the tendency to get more charge in Fe–O octahedral compared with that in Ti–O octahedral, leading to an enhanced electronegativity in doped Ca 3 Ti 2 O 7. [ABSTRACT FROM AUTHOR]

• The hierarchical CoRu-LDH/PANI nanowires was rationally designed via a facile hydrothermal-depositional strategy. • The PANI coating can elevate the valence states of Co/Ru atoms in CoRu/LDH and afford a superhydrophilic surface. • The CoRu-LDH/PANI exhibits a superior alkaline HER activity and stability at large current density. Promoting the dissociation of water and desorption of hydrogen are both crucial challenges for improving the hydrogen evolution reaction (HER) activity and stability in alkaline media, especially at large current densities. Herein, we demonstrate a polyaniline-coated CoRu-LDH (CoRu-LDH/PANI) nanowire array electrocatalyst for efficient and stable alkaline HER. Benefiting from the optimized electronic structure and surface properties, the as-prepared CoRu-LDH/PANI shows an excellent HER activity with low overpotentials of 250, and 275 mV, respectively, at large current densities of 500 and 1000 mA cm−2 in 1.0 M KOH, superior to the benchmark 20% Pt/C and the pristine CoRu-LDH. Furthermore, CoRu-LDH/PANI exhibits an unprecedented stability at a large current density of 500 mA cm−2 even after 50 h. The combined experimental and density functional theory (DFT) investigations reveal that PANI coating not only performs as an electronic regulator to lift the valence states and reduces the binding strength to hydrogen intermediates, leading to the superior HER performance, but also affords a superhydrophilic surface to promote the rapid transport of electrolytes and bubbles, which is crucial for the long-term stability at large current density. This work provides an effective guidance for engineering efficient alkaline HER eletrocatalysts towards practical water electrolysis. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to its unique properties, such as long carrier diffusion length and adjustable optical band gap, organic-inorganic hybrid perovskite has been a potentially strong photoelectric material for solar cells. However, the challenge of insufficient stability of perovskite materials has not been solved, which in turn, limits its commercial application. Inspired by the strong stability of C 3 N 2 H 5 PbI 3 (ImPbI 3), we present an innovative doped system, Im (1- x) Cs x PbI 3 (x = 0.25, 0.5, 0.75), based on the cation-doped strategy, to obtain both strong stability and excellent photoelectric performance. A new perovskite phase ImPbI 3 is proposed and verified rationality of existence through formation energy, ab initio molecular dynamics (AIMD), mean square displacement (MSD), and X-ray diffraction (XRD) based on density functional theory (DFT) calculations. For analyzing the photoelectric properties of Im (1- x) Cs x PbI 3 , the bandgap, charge distribution of the frontier molecular orbital, and projected density of states are investigated. To study the stability of Im (1- x) Cs x PbI 3 , geometric configuration, tolerance factor, crystal orbital Hamilton populations (COHP), and AIMD simulations are performed. The results show that the perovskite phase ImPbI 3 has strong thermodynamic stability and structural stability, and its optical bandgap value is lower than that of the hexagonal system. When the content of doped Cs does not exceed 50%, the stability of the perovskite phase ImPbI 3 is significantly improved. Comprehensive analysis shows that Im 0.5 Cs 0.5 PbI 3 exhibits encouraging performance with strong stability and high optical absorption coefficient. This theoretical study opens a new avenue for the design of robust organic-inorganic hybrid perovskite materials with strong stability and excellent photoelectric performance based on our findings from perovskite phase ImPbI 3 system. [Display omitted] • A new perovskite phase of C 3 N 2 H 5 PbI 3 (ImPbI 3) is proposed • An innovative doped system, Im (1- x) Cs x PbI 3 (x = 0.25, 0.5, 0.75) • Stability and photoelectric properties are improved through doping [ABSTRACT FROM AUTHOR]

Developing catalysts with high activity, durability, and water resistance for ozone decomposition is crucial to regulate the pollution of ozone in the troposphere, especially in indoor air. To overcome the shortcomings of metal oxide catalysts with respect to their durability and water resistance, Fe-Co double-atom catalyst (DAC) is proposed as a novel catalyst for ozone decomposition. Here, through a systematic study using density functional theory (DFT) calculations and microkinetic modeling, the adsorption and catalytic decomposition of O 3 on Fe-Co DAC have been examined based on adsorption configuration, orbital hybridization, and electron transfer. Based on Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction mechanisms, the mechanisms of ozone decomposition on Fe-Co DAC were explored by analyzing reaction paths and energy variations. To confirm the water-resistant of Fe-Co DAC, competitive adsorption behavior between O 3 and dominant environmental gases was discussed through ab initio molecular dynamic (AIMD) simulation. The dominant reaction mechanism of ozone decomposition is L-H and the rate-determining step is the desorption of the first oxygen molecule from the surface of Fe-Co DAC which has an energy barrier of 0.78 eV. Due to this relatively low energy barrier and high turnover frequency (TOF), the optimal operation window of catalytic O 3 decomposition on Fe-Co DAC is <500 K suggesting that catalytic decomposition of O 3 on Fe-Co DAC can occur at room temperature. This theoretical study provides new insights for designing novel catalysts for ozone decomposition and fundamental guidance for subsequent experimental research. [Display omitted] • A novel Fe-Co double-atoms catalyst for O 3 decomposition. • Fe-Co DACs with high low-temperature activity and strong water-resistant. • Reaction mechanism in atomic level and microkinetic modeling. [ABSTRACT FROM AUTHOR]