Search

Owing to the clean and environment friendly advantages, electrochemical water splitting stands out among various hydrogen production strategies. Electrocatalysts play an important role in the hydrogen evolution reaction (HER). Hence, Pt-(Ni0.5Co0.5)2P/S-carbon fibers as electrocatalysts for highly efficient HER were prepared through the structural designing of CNF and heteroatom doping (sulfur (S) or boron (B)). First, three composites of the (Ni0.5Co0.5)2P/carbon fiber ((Ni0.5Co0.5)2P/CNF), (Ni0.5Co0.5)2P/porous carbon fiber ((Ni0.5Co0.5)2P/PCNF), and (Ni0.5Co0.5)2P/hollow porous carbon fiber ((Ni0.5Co0.5)2P/HPCNF) were fabricated via a facile electrospinning with a solvothermal method. (Ni0.5Co0.5)2P/PCNFs showed the smallest overpotential at a current density of 10 mA cm−2 among the three structures. (Ni0.5Co0.5)2P nanosheets loaded on the porous CNF with a large active surface area may expose active sites and shorten the ion transport channel. To improve the catalytic performance of (Ni0.5Co0.5)2P/PCNF, Pt nanoparticles were anchored on (Ni0.5Co0.5)2P/heteroatom doped-PCNF by the chemical reduction method. Pt-(Ni0.5Co0.5)2P/S doped-PCNF exhibited a small overpotential of 64 mV for the HER with 74.9 mV dec−1 Tafel slope and a good stability, which was attributed to the conductive S-doped PCNF facilitating electron transport, accompanying the synergistic effect between the bimetallic phosphide and Pt nanoparticles, thus providing a facile method for an efficient HER electrocatalysis. [ABSTRACT FROM AUTHOR]

Developing multicomponent hybrid materials is an effective method to achieve structurally stable anode materials for high-performance sodium-ion batteries (SIBs). In this work, mesoporous Fe2O3 nanospheres wrapped by heteroatom pre-intercalated Cl-terminated Ti3C2Tx MXene as SIB anode materials are designed. The Cl-terminated Ti3C2Tx MXene is obtained via a Lewis acidic etching route, which offers a green and practicable route to etching MAX precursors without HF. The MXene framework is pretreated with borohydride and thus turns into a 3D structure to better support Fe2O3 nanospheres. In order to obtain the Fe2O3@Ti3C2Tx anode, Fe2O3 nanospheres are distributed on the Ti3C2Tx MXene framework by virtue of the surfactant CTAB. Benefiting from the synergic effect of Fe2O3 nanospheres and a heteroatom-doped MXene framework, which can decrease the Na ion diffusion barrier, this unique structure provides abundant ionic transfer paths and active sites to accelerate the electrochemical process. Furthermore, the volume change of Fe2O3 nanospheres can be effectively alleviated during the sodiation/desodiation process. Herein, the resultant Fe2O3@Ti3C2Tx anode shows excellent sodium storage performance, high reversible capacity (350 mA h g−1 at 1.0 A g−1 after 200 cycles), considerable long-cycle stability (262.8 mA h g−1 at 2.0 A g−1 after 800 cycles) and calculated b values of the cathodic and anodic peaks are 0.89 and 0.94, respectively. All these analyses boost the commercial process of Fe2O3@MXene hybrids in SIBs. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs), especially cobalt-based sulfides have great potential use in battery anode materials. However, low coulombic efficiency and poor cycle stability limit their application in battery fabrication. In this work, a two-dimensional MOF material ZIF-9 was treated by a two-step calcination method that obtained a flower-shaped carbon skeleton coated with Co-vacancy, Co1−xS nanoparticles. The skeleton effectively restrains the volume expansion that happens on electrodes, which improved the electrical conductivity of the compound. The cobalt vacancy changes the local electronic structure and atomic populations; the DFT calculation also proves that this structure is beneficial to the migration of sodium ions and provides good cycling performance under high current density. According to our electronic experiments, Co1−xS@C exhibited good electrochemical performance, which maintains a capacity of about 300 mA h g−1 at a high current density of 5 A g−1 after 250 cycles. All results indicate the outstanding electrochemical performance of our composite material, especially under a high current density. This work may provide a method in MOFs-derived TMSs compounds to stimulate the potential of transition metal sulfide materials in energy storage. [ABSTRACT FROM AUTHOR]