P-doped cobalt carbonate hydroxide@NiMoO4 double-shelled hierarchical nanoarrays anchored on nickel foam as a bi-functional electrode for energy storage and conversion.

The rational structure design and controllable surface modification of electrode materials plays a decisive role in constructing high performance energy storage and conversion devices. Herein, the P-doped cobalt carbonate hydroxide@NiMoO4 (P-CoCH@NiMoO4) nanowires@nanosheets double-shell hierarchical structure is successfully fabricated on nickel foam. The unique nanowire@nanosheet structure with gradient porous distribution and hydrophilic nature can facilitate both the charge and electron transfer based on the synergetic effects with conductive NiMoO4 array. Importantly, the dopant of P element can enrich oxygen vacancies on the surface of CoCH nanowire, thus increase the effective active sites and enhance the electrocatalytic performance. Therefore, when act as the supercapacitor electrode, the bi-functional P-CoCH@NiMoO4/NF material achieves high areal capacitance (5.08 F cm-2 at 2 mA cm-2, 0.75 mAh cm-2) and good cyclic stability (82.7% capacitance retention after 2000 cycles). Meanwhile, when utilize as the hydrogen evolution electrode in alkaline solution, a low overpotential (115 mV at 10 mA cm-2) and Tafel slope (113.5 mV dec-1) can also be achieved.

A multidimensional rational design of nickel-iron sulfide and carbon nanotubes on diatomite via synergistic modulation strategy for supercapacitors.

Based on their characteristics, transition metal layered double hydroxides have been of great scientific interest for their use in supercapacitors. Up until now, severe aggregation and low intrinsic conductivity have been the major hurdles for their application. In this work, nickel-iron sulfide nanosheets (NiFeSx) and carbon nanotubes (CNTs) were synthesized on diatomite using chemical vapor deposition and a two-step hydrothermal method to overcome these challenges. Synthesis of this composite successfully exploits the synergistic effect of multicomponent materials to improve the electrochemical performance. Diatomite is selected as a substrate to provide preferable surroundings for the uniform dispersion of nanomaterial on its surface, which enlarges the active sites that come in contact with the electrolytes, significantly improving the electrochemical properties. Combined with high conductivity and a synchronous sulfurization effect, the NiFeSx@CNTs@MnS@Diatomite electrode delivered a high specific capacitance of 552F g-1 at a current density of 1 A g-1, a good rate capability of 68.4% retention at 10 A g-1, and superior cycling stability of 89.8% capacitance retention after 5000 cycles at 5 A g-1. Furthermore, an asymmetric supercapacitor assembled via NiFeSx@CNTs@MnS@Diatomite and graphene delivered a maximum energy density of 28.9 Wh kg-1 and a maximum power density of 9375 W kg-1 at a potential of 1.5 V. This research lays the groundwork for ideal material preparation as well as a rational design for the electrode material, including property enhancement of diatomite-based material for use in supercapacitors.

Morphology-controlled synthesis of CoMoO4 nanoarchitectures anchored on carbon cloth for high-efficiency oxygen oxidation reaction.

Novel CoMoO4 nanoarrays with different morphologies are anchored on a carbon cloth via a simple hydrothermal method by adjusting the Co/Mo atom ratio. The in situ growth and tight immobilization of the CoMoO4 nanocomposite on the carbon cloth can facilitate the electrolyte infiltration and electrons transfer rate at the contact interface. Therefore, the free-standing electrode of CoMoO4/carbon cloth with interconnected nanosheets shows superior electrocatalytic activity, and the overpotential of 286 mV is obtained at 15 mA cm-2 in alkaline solution. Moreover, the catalyst also exhibits a small Tafel slope of 67 mV dec-1 as well as good stability. The relationship between the active material morphology, contact interface and the electrocatalytic performance is also discussed. As the carbon cloth is commercially available, this simple but effective structural controlling method demonstrates a new large-scale practical electrode fabrication technique for high performance OER electrodes and large-scale water splitting.