CoFe -CoFe2O4/N-doped carbon nanocomposite derived from in situ pyrolysis of a single source precursor as a superior bifunctional electrocatalyst for water splitting

Self-assembled mesostructured Co0.5Fe2.5O4 nanoparticle superstructures for highly efficient oxygen evolution

Self-assembly of colloidal nanoparticles (NPs) into well-defined superstructures has been recognized as one of the most promising ways to fabricate rationally-designed functional materials for a variety of applications. Introducing hierarchical mesoporosity into NP superstructures will facilitate mass transport while simultaneously enhancing the accessibility of constituent NPs, which is of critical importance for widening their applications in catalysis and energy-related fields. Herein, we develop a colloidal co-assembly strategy to construct mesostructured, carbon-coated Co_0.5Fe_2.5O₄ NP superstructures (M-C@CFOSs), which show great promise as highly efficient electrocatalysts for the oxygen evolution reaction (OER). Specifically, organically-stabilized SiO₂ NPs are employed as both building blocks and sacrificial template, which co-assemble with Co_0.5Fe_2.5O₄ NPs to afford binary NP superstructures through a solvent drying process. M-C@CFOSs are obtainable after in situ ligand carbonization followed by the selective removal of SiO₂ NPs. The hierarchical mesoporous structure of M-C@CFOSs, combined with the conformal graphitic carbon coating derived from the native organic ligands, significantly improves their electrocatalytic performance as OER electrocatalysts when compared with nonporous Co_0.5Fe_2.5O₄ NP superstructures. This work establishes a new and facile approach for designing NP superstructures with hierarchical mesoporosity, which may find wide applications in energy storage and conversion.

Non-precious-metal catalysts for alkaline water electrolysis: operando characterizations, theoretical calculations, and recent advances

Advances of non-precious-metal catalysts for alkaline water electrolysis are reviewed, highlighting operando techniques and theoretical calculations in their development.

Porous Anatase-TiO2(B) Dual-Phase Nanorods Prepared from in Situ Pyrolysis of a Single Molecule Precursor Offer High Performance Lithium-Ion Storage

To overcome the problems faced by TiO₂ materials for lithium-ion batteries usage, such as easy nanoparticles agglomeration during cycling and poor cycling performance, in this study, TiO₂ nanorods with the controlled phase compositions are prepared via direct pyrolysis of single molecule precursors in combination with a simple washing process. By tuning the external cations in the single source precursors, three TiO₂ samples in a nanorod shape with the compositions of pure anatase, anatase-rutile dual phase, and anatase-TiO₂(B) dual phase are synthesized successfully. High-resolution transmission electron microscopy, X-ray powder diffraction, and Raman measurements confirm the phase structures and compositions of the three prepared samples. The electrochemical results manifest that all the three nanorod-shaped TiO₂ samples show the long-term cycling stability as negative materials for LIBs. Among them, the TiO₂ sample with the combination of the anatase and TiO₂-B phase shows the best performance, with the specific capacity of ∼184, 164, 140, 105, 80, and 60 mAh g^-1 at 0.1, 0.3, 0.5, 1.5, 3.0, and 5.0 A g^-1, respectively, and showing no capacity loss and low resistance after 1000 cycles at 1.5 A g^-1. By the analysis of the cyclic voltammetry results recorded from different scan rates, the lithium-ion storage mechanism is clarified, which is dominated by the semi-infinite linear diffusion (anatase phase) in combination with the partial surface pseudocapacitive contribution [TiO₂(B) phase]. As a result, this sample shows a great potential as a negative material for LIBs because of its electrochemical stability, high specific capacity, and superior rate capability. The proof-of-concept design of the anatase and TiO₂-B dual phase may provide a new strategy for the synthesis of high performance TiO₂-based anode material for LIBs.