Hierarchical FeCo/C@Ni(OH)2 heterostructures for enhanced oxygen evolution activity

Unveiling the Promotion of Fe in Ni3S2 Catalyst on Charge Transfer for the Oxygen Evolution Reaction

In recent years, catalysts based on transition metal sulfides have garnered extensive attention due to their low cost and excellent electrocatalytic activity in the alkaline oxygen evolution reaction. Here, the preparation of Fe-doped Ni3S2 via a one-step hydrothermal approach is reported by utilizing inexpensive transition metals Ni and Fe. In an alkaline medium, Fe-Ni3S2 exhibits outstanding electrocatalytic activity and stability for the OER, and the current density can reach 10 mA cm-2 with an overpotential of 163 mV. In addition, Pt/C||Fe-Ni3S2 is used as the membrane electrode of the anion exchange membrane water electrolyzer, which is capable of providing a current density of 650 mA cm-2 at a cell voltage of 2.0 V, outperforming the benchmark Ir/C. The principle is revealed that the doping of Fe enhances the electrocatalytic water decomposition ability of Ni3S2 by in situ Raman and in situ X-ray absorption fine structure. The results indicate that the doping of Fe decreases the charge density near Ni atoms, which renders Fe-Ni3S2 more favorable for the adsorption of OH- and the formation of *OO- intermediates. This work puts forward an effective strategy to significantly improve both the alkaline OER activity and stability of low-cost electrocatalysts.

Unveiling the Nature of Superior Sodium Storage in the CoSe2/rGO Nanocomposite

Sodium-ion batteries (SIBs) are considered the most promising alternatives to lithium-ion batteries (LIBs) due to the abundant availability of sodium and their cost-effectiveness. Transition metal selenides (TMSes) are considered promising anodes for SIBs due to their economic efficiency and high theoretical capacity. Nevertheless, overcoming the challenges of sluggish reaction kinetics and severe structural damage is crucial to improving cycle life and rate capability. Herein, a simple microwave hydrothermal process was used to synthesize a nanocomposite of CoSe2 nanoparticles uniformly anchored on reduced graphene oxide nanosheets (CoSe2/rGO). The influences of rGO on the structure and electrochemical performance and Na+ diffusion kinetics are investigated through a series of characterization and electrochemical tests. The resulting CoSe2/rGO nanocomposite exhibits a remarkable initial specific capacity of 544 mAh g-1 at 0.5 A g-1, impressive rate capability (368 mAh g-1 at 20 A g-1), and excellent cycle life and maintains 348 mAh g-1 at 5 A g-1 over 1200 cycles. In addition, the in situ electrochemical impedance spectroscopy (EIS), ex situ X-ray diffraction (XRD), and transmission electron microscopy (TEM) tests are selected to further investigate the sodium storage mechanism.

Coupling Interface Construction of Ni(OH)2/MoS2 Composite Electrode for Efficient Alkaline Oxygen Evolution Reaction

The transition metal-based catalysts have excellent electrochemical oxygen evolution reaction catalytic activity in alkaline electrolytes, attracting a significant number of researchers’ attention. Herein, we used two-step hydrothermal and solvothermal methods to prepare a Ni(OH)2/MoS2/NF electrocatalyst. The electrocatalyst displayed outstanding OER activity in 1.0 M KOH electrolyte with lower overpotential (296 mV at 50 mA·cm−2) and remarkable durability. Comprehensive analysis shows that reinforcement of the catalytic function is due to the synergistic effect between Ni(OH)2 and MoS2, which can provide more highly active sites for the catalyst. This also provides a reliable strategy for the application of heterogeneous interface engineering in energy catalysis.