Nanoscale Oxygenous Heterogeneity in FePC Glass for Highly Efficient and Reusable Catalytic Performance.

Metallic glass, with its unique disordered atomic structure and high density of low-coordination sites, is regarded as the most competitive new catalyst for environmental catalysis. However, the efficiency and stability of metallic glass catalysts are often affected by their atomic configuration. Thus, the design and regulation of the nanoscale structure of metallic glasses to improve their catalytic efficiency and stability remains a challenge. Herein, a non-noble component, Fe75 P15 C10 amorphous ribbon, is used as a precursor to fabricate a hierarchical gradient catalyst with nanoscale heterogeneous and oxygenous amorphous structure by simple annealing and acid-immersing. The resulting catalyst offers an ultrahigh catalytic ability of kSA• C0 = 3101 mg m-2  min-1 and excellent reusability of 39 times without efficiency decay in dye wastewater degradation. Theoretical calculations indicate that the excellent catalytic performance of the catalyst can be attributed to its unique heterogeneous nanoglass structure, which induces oxygen atoms. Compared to the FePC structure, the FeP/FePCO structure exhibits strong charge transferability, and the energy barrier of the rate-determining steps of the conversion of S2 O8 2- to SO4 -• is reduced from 2.52 to 0.97 eV. This study reveals that a heterogeneous nanoglass structure is a new strategy for obtaining high catalytic performance.

Superimposed Effect of La Doping and Structural Engineering to Achieve Oxygen-Deficient TiNb2O7 for Ultrafast Li-Ion Storage.

TiNb2O7 (TNO) is a competitive candidate of a fast-charging anode due to its high specific capacity. However, the insulator nature seriously hinders its rate performance. Herein, the La3+-doped mesoporous TiNb2O7 materials (La-M-TNO) were first synthesized via a facile one-step solvothermal method with the assistance of polyvinyl pyrrolidone (PVP). The synergic effect of La3+ doping and the mesoporous structure enables a dual improvement on the electronic conductivity and ionic diffusion coefficient, which delivers an impressive specific capacity of 213 mAh g-1 at 30 C. The capacity retention (@30C/@1C) increases from 33 to 53 and 74% for TNO, M-TNO, and La-M-TNO (0.03), respectively, demonstrating a step-by-step improvement of rate performance by making porous structures and intrinsic conductivity enhancement. DFT calculations verify that the enhancement in electronic conductivity due to La3+ doping and oxygen vacancy, which induce localized energy levels via slight hybridization of O 2p, Ti 3d, and Nb 4d orbits. Meanwhile, the GITT result indicates that PVP-induced self-assembly of TNO accelerates the lithium ion diffusion rate by shortening the Li+ diffusion path. This work verifies the effectiveness of the porous structure and highlights the significance of electronic conductivity to rate performance, especially at >30C. It provides a general approach to low-conductivity electrode materials for fast Li-ion storage.

Oxide Nanoclusters on Ti3 C2 MXenes to Deactivate Defects for Enhanced Lithium Ion Storage Performance.

The commercialization of MXenes as anodes for lithium-ion batteries is largely impeded by low initial coulombic efficiency (ICE) and unfavorable cycling stability, which are closely associated with defects such as Ti vacancies (VTi ) in Ti3 C2 MXenes. Herein, an effective strategy is developed to deactivate VTi defects by in situ growing Al2 O3 nanoclusters on MXenes to alleviate the irreversible electrolyte decomposition and Li dendrites formation trend induced by defects, improving ICE and cycling stability. Furthermore, it is revealed that excessively lithiophilic VTi defects would impede Li ions diffusion due to their strong adsorption, leading to a locally nonuniform Li flux to these "hot spots," setting scene for the formation of Li dendrites. The Al2 O3 nanoclusters anchored on VTi sites can not only improve Li diffusion kinetics but also promote the homogeneous solid electrolyte interphase formation with small charge transfer resistance, achieving uniform Li deposition in a smaller overpotential without formation of Li dendrites. As expected, Ti3 C2 @Al2 O3 -11 electrode delivers a high ICE of 76.6% and an outstanding specific capacity of 285.5 mAh g-1 after 500 cycles, which is much higher than that of pristine Ti3 C2 sample. This work sheds light on modulating defects for high-performance energy storage materials.

Metal-Organic Framework-Derived Nitrogen-Doped Cobalt Nanocluster Inlaid Porous Carbon as High-Efficiency Catalyst for Advanced Potassium-Sulfur Batteries.

Despite high theoretical capacity and earth-abundant resources, the potential industrialization of potassium-sulfur (K-S) batteries is severely plagued by poor electrochemical reaction kinetics and a parasitic shuttle effect. Herein, a facile low-temperature pyrolysis strategy is developed to synthesize N-doped Co nanocluster inlaid porous N-doped carbon derived from ZIF-67 as catalytic cathodes for K-S batteries. To maximize the utilization efficiency, the size of Co nanoparticles can be tuned from 7 nm to homogeneously distributed 3 nm clusters to create more active sites to regulate affinity for S/polysulfides, improving the conversion reaction kinetics between captured polysulfides and K2S3/S, fundamentally suppressing the shuttle effect. Cyclic voltammetry curves, Tafel plots, electrochemical impedance spectroscopy, and density functional theory calculations ascertain that 3 nm Co clusters in S-N-Cos-C cathodes exhibit superior catalytic activity to ensure low charge transfer resistance and energy barriers, enhanced exchange current density, and improved conversion reaction rate. The constructed S-N-Cos-C cathode delivers a superior reversible capacity of 453 mAh g-1 at 50 mA g-1 after 50 cycles, a dramatic rate capacity of 415 mAh g-1 at 400 mA g-1, and a long cycling stability. This work provides an avenue to make full use of high catalytic Co nanoclusters derived from metal-organic frameworks.

Encapsulating Ultrafine Sb Nanoparticles in Na+ Pre-Intercalated 3D Porous Ti3C2Tx MXene Nanostructures for Enhanced Potassium Storage Performance.

Taking into consideration the advantages of the highly theoretical capacity of antimony (Sb) and abundant surface redox reaction sites of Na+ pre-intercalated 3D porous Ti3C2Tx (Na-Ti3C2Tx) architectures, we elaborately designed the Sb/Na-Ti3C2Tx hybrid with Sb nanoparticles homogeneously distributed in 3D porous Na-Ti3C2Tx architectures through a facile electrostatic attraction and carbothermic reduction process. Na-Ti3C2Tx architectures with more open structures and larger active specific surface area not only could certainly alleviate volume changes and hinder the aggregation of Sb nanoparticles in the cycling process to improve the structural stability but also significantly strengthen the electron-transfer kinetics and provide unblocked K+ diffusion channels to promote ionic/electronic transport rate. Furthermore, the ultrafine Sb nanoparticles could efficiently shorten K+ transport distance and expose more accessible active sites to improve capacity utilization. DFT calculations further indicate that the Sb/Na-Ti3C2Tx anode effectively decreases the adsorption energy of K+ and accelerates the potassiation process. Benefiting from the synergistic effect, it exhibits an outstanding specific capacity of 392.2 mAh g-1 at 0.1 A g-1 after 450 cycles and a stable capacity reservation with a capacity fading rate of 0.03% per cycle at 0.5 A g-1. Our work may encourage further research on advanced MXene-based hybrid materials for high-performance PIBs.