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To inhibit the agglomeration of tin-based nanomaterials and simplify the complicated synthesis process, a facile and eco-friendly self-formed template method is reported to synthesize tin submicron spheres dispersed in nitrogen-doped porous carbon (Sn/NPC) by pyrolysis of a mixture of disodium stannous citrate and urea. The vital point of this strategy is the formation of Na2CO3 templates during pyrolysis. This self-formed Na2CO3 acts as porous templates to support the formation of NPC. The obtained NPC provides good electronic conductivity, ample defects, and more active sites. Serving as anode for Li-ion batteries, the Sn/NPC electrode obtains a stable discharge capacity of 674.1 mAh/g after 150 cycles at 0.1 A/g. Especially, a high discharge capacity of 331.2 mAh/g can be achieved after 1100 cycles at 3 A/g. Additionally, a full cell coupled with LiCoO2 as cathode yields a discharge capacity of 524.8 mAh/g after 150 cycles at 0.1 A/g. In-situ XRD is implemented to investigate the alloying/dealloying reaction mechanisms. Density functional theory calculation ulteriorly explicates that NPC heightens intrinsic electronic conductivity, and NPC especially pyrrolic-N and pyridinic-N doping facilitates the Li-adsorption ability. Climbing image nudged elastic band method reveals low Li+ diffusion energy barrier in presence of N atoms, which accounts for the terrific electrochemical properties of Sn/NPC electrode.

Green synthesis of porous anode materials with high performance and low cost remains a great challenge for the lithium-ion battery industry at present. Herein, we propose a green strategy to synthesize Sn submicron spheres/porous carbon (denoted as Sn/PC) composites by the direct carbonization of disodium stannous citrate, which is composed of Sn submicron spheres supported by porous carbon. Self-generated Na2CO3 during carbonization serves as the template to support the formation of porous carbon. The obtained porous carbon can efficaciously constrain the aggregation of Sn and prevent the volume expansion of Sn submicron spheres. Such particular structural characteristics endow the Sn/PC electrode with high discharge capacity (588 mA h g−1 after 200 cycles at 100 mA g−1) and long cycle life (431.8 mA h g−1 after 2000 cycles at 1200 mA g−1). Meanwhile, the full cell paired with the LiCoO2 cathode affords a high discharge capacity of 511.4 mA h g−1. The in-depth insights into the lithium storage mechanisms of the electrode are investigated by in situ XRD technique. The conductivity performance for the heterointerface of Sn and C is systematically studied by density functional theory calculations. This green strategy can initiate new horizons for fabricating other anode materials with conspicuous volume expansion.

Metal halide perovskite quantum dots, with high light-absorption coefficients and tunable electronic properties, have been widely studied as optoelectronic materials, but their applications in photocatalysis are hindered by their insufficient stability because of the oxidation and agglomeration under light, heat, and atmospheric conditions. To address this challenge, herein, we encapsulated CsPbBr3 nanocrystals into a stable iron-based metal-organic framework (MOF) with mesoporous cages (∼5.5 and 4.2 nm) via a sequential deposition route to obtain a perovskite-MOF composite material, CsPbBr3@PCN-333(Fe), in which CsPbBr3 nanocrystals were stabilized from aggregation or leaching by the confinement effect of MOF cages. The monodispersed CsPbBr3 nanocrystals (4-5 nm) within the MOF lattice were directly observed by transmission electron microscopy and corresponding mapping analysis and further confirmed by powder X-ray diffraction, infrared spectroscopy, and N2 adsorption characterizations. Density functional theory calculations further suggested a significant interfacial charge transfer from CsPbBr3 quantum dots to PCN-333(Fe), which is ideal for photocatalysis. The CsPbBr3@PCN-333(Fe) composite exhibited excellent and stable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities in aprotic systems. Furthermore, CsPbBr3@PCN-333(Fe) composite worked as the synergistic photocathode in the photoassisted Li-O2 battery, where CsPbBr3 and PCN-333(Fe) acted as optical antennas and ORR/OER catalytic sites, respectively. The CsPbBr3@PCN-333(Fe) photocathode showed lower overpotential and better cycling stability compared to CsPbBr3 nanocrystals or PCN-333(Fe), highlighting the synergy between CsPbBr3 and PCN-333(Fe) in the composite.

Molybdenum disulfide, as an electronic highly-adjustable catalysts material, tuning its electronic structure is crucial to enhance its intrinsic hydrogen evolution reaction (HER) activity. Nevertheless, there are yet huge challenges to the understanding and regulation of the surface electronic structure of molybdenum disulfide-based catalysts. Here we address these challenges by tuning its electronic structure of phase modulation synergistic with interfacial chemistry and defects from phosphorus or sulfur implantation, and we then successfully design and synthesize electrocatalysts with the multi-heterojunction interfaces (e.g., 1T0.81-MoS2@Ni2P), demonstrating superior HER activities and good stabilities with a small overpotentials of 38.9 and 95 mV at 10 mA/cm2, a low Tafel slopes of 41 and 42 mV/dec in acidic as well as alkaline surroundings, outperforming commercial Pt/C catalyst and other reported Mo-based catalysts. Theoretical calculation verified that the incorporation of metallic-phase and intrinsic HER-active Ni-based materials into molybdenum disulfide could effectively regulate its electronic structure for making the bandgap narrower. Additionally, X-ray absorption spectroscopy indicate that reduced nickel possesses empty orbitals, which is helpful for additional H binding ability. All these factors can decrease Mo-H bond strength, greatly improving the HER catalytic activity of these materials., The understanding and regulation of the surface electronic structure of molybdenum disulfide-based catalysts for hydrogen evolution reaction (HER) remains a challenges. Here, the authors design and synthesize electrocatalysts with multi-heterojunction interfaces showing enhanced HER activities and stabilities.

Accurate determination of the atomic spatial configuration of Frenkel defects is important for understanding the mechanism and fully utilizing these defects to optimize the material properties. In this study, aberration-corrected scanning transmission electron microscopy (STEM) was used to identify the Fe vacancies and Fe Frenkel defect pairs, which have not been previously investigated, in NiFe2O4 (NFO). The spatial distribution of these point defects is determined by comparing the experimental and simulated images, where the experimental image intensities are consistent with the calculated image intensities. We confirmed the stabilities of the observed point defect configurations and calculated their electronic structures using density functional theory. A comprehensive understanding of the relationship between the Frenkel defect spatial configurations and electronic properties is obtained, which provides an alternative method to regulate the NFO performance.

Incomplete absorption of antibiotics leads to environmental damage, which has aroused strong and urgent attention. To solve this problem, in this paper, we first proposed oxygen vacancy (OVs) and Zn ion doping synergy BiOBr (Zn-VBOB) photocatalyst. The results show the degradation rate constants of Zn-VBOB for carbamazepine (CBZ) and sulfamethoxazole (SMX) were 10.15 and 2.5 times higher than that of undoped BiOBr, respectively, and higher than the single Zn-doped or OVs involved ones. Zn-VBOB can generate more types of radicals as the degradation active species in comparison of the single Zn or OVs introduced ones in which the mechanism was systematically studied by radical capture experiment and DFT calculation. The shortened band-gap resulted in the easier h+-e- separation, accounting for the more significant factor for the reactive radicals generation than by depressing the recombination trend, which proposed a new perspective for enhancing the degradation of broad-spectrum antibiotics

Anion exchange membranes (AEMs) are an important component in anion exchange membrane fuel cells, and their side chain structures have a significant impact on membrane performance. Here, we construct a series of poly(phenylene oxide) (PPO)-based AEMs with varied side chain structures and investigate the effects of alkyl or alkoxyl extenders (or “tail” of the cation) and spacers (or the link between backbone and cation head group) on AEM performance. Our investigations demonstrate that the simultaneous introduction of alkoxyl extender and spacer can significantly improve water absorption and ion conductivity of membrane; this is attributed to the good hydrophilicity of alkoxyl group and flexibility of spacer that benefit the formation hydrophilic domains. At an IEC (ion exchange capacity) of 1.13 mmol/g, the AEM containing both spacer and alkoxyl extender exhibits a hydroxide conductivity of 87.3 mS/cm (80 °C), which is much higher than that of other spacer-containing membranes at similar IECs. The H2/O2 single cell constructed with this membrane exhibits a good peak power density of 292 mW/cm2 at 60 °C. In addition, the steric hindrance of the extender gives rise to higher alkali stability of the AEM than that of the membrane which does not have the extender. Our work provides a meaningful direction of side chain design which can effectively improve conductivity and alkaline stability of AEMs.

Dual improvement on electronic conductivity and ionic conductivity of TiNb2O7 (TNO) is of great significance for realizing high-performance lithium-ion batteries. In this work, the V5+-doped TNO microspheres (denoted as Vx-TNOMs, x = 0, 0.015, 0.030 and 0.045) were synthesized via a simple solvothermal approach. X-ray diffraction coupled with Rietveld refinements and Raman spectra analyses verified that V5+ not simply possessed substitution doping mode but also inserted into the interstices of the TNOMs lattice. The density functional theory (DFT) calculations indicated that the improved electronic conductivity could originate from the formation of impurity bands after the V5+ doping. Meanwhile, the climbing image-nudged elastic band (CI-NEB) demonstrated that a TNOMs framework with faster ion transport pathways is achieved by the V5+ doping. Served as anode material of lithium-ion batteries, the V0.030-TNOMs electrode presents an impressive discharge capacity of 163.5 mAh/g at 10 C and long cycle life up to 2000 cycles with a capacity fading of merely 0.014% per cycle. Furthermore, the full battery employing V0.030-TNOMs as an anode and commercial LiCoO2 as a cathode exhibits superior electrochemical performances with promising application prospect. Our present study sheds new light on constructing high-performance electrodes for electrochemical energy storage.