Designing and constructing bifunctional electrocatalysts is vital for water splitting. Particularly, the rational interface engineering can effectively modify the active sites and promote the electronic transfer, leading to the improved splitting efficiency. Herein, free‐standing and defect‐rich heterogeneous MoS 2 /NiS 2 nanosheets for overall water splitting are designed. The abundant heterogeneous interfaces in MoS 2 /NiS 2 can not only provide rich electroactive sites but also facilitate the electron transfer, which further cooperate synergistically toward electrocatalytic reactions. Consequently, the optimal MoS 2 /NiS 2 nanosheets show the enhanced electrocatalytic performances as bifunctional electrocatalysts for overall water splitting. This study may open up a new route for rationally constructing heterogeneous interfaces to maximize their electrochemical performances, which may help to accelerate the development of nonprecious electrocatalysts for overall water splitting.

a great deal of research effort has been devoted on high energy density supercapacitors. According to the equation of energy density E = 1/2 CV 2 , the energy density (E) of supercapacitors can be enhanced by increasing either voltage window (V) or specific capacitance (C). [5] For high specific capacitance, one of the research efforts should concentrate on using transition metal oxides (TMO) (e.g., MnO 2 , RuO 2 ) as electrode materials. [6,7] They can provide great specific capacitance due to the pseudocapacitive characteristic. [8,9] Among TMO materials, MnO 2 is one of the most potential materials for supercapacitors due to its high theoretical specific capacitance, environmental friendliness, and the high practical voltage window (about 1 V). [2] However, it has suffered from intrinsically low conductivity and specific surface area, which severely restrict its further development in practical application of supercapacitors. In this regard, integrating nanostructured MnO 2 and conductive carbon materials to fabricate novel hybrid nanostructures is a plausible solution to overcome this obstacle. [4] Further, some research efforts have been accordingly performed to synthesize hybrid nanostructures electroactive materials for constructing supercapacitors with considerable performance. Some researchers accordingly synthesized highperformance nanostructured MnO 2 -carbon materials electrodes, whose specific capacitance is close to theoretical value. However, the undesirable contact resistances that produced by the weak and noncoherent TMO/conductor interfaces lead to sluggish kinetics for charge transport, which requires further improvement. [10,11] In order to further improve the energy density, some researchers have concentrated on enlarging the voltage window of supercapacitors. The applications of aqueous electrolytes have been limited by their theoretical voltage window (≈1.23 V) and the practical voltage window is mostly lower than about 1 V for supercapacitors. [12] To extend the voltage window, various techniques have been applied, such as dual shuttle-ion electrolytes, [13,14] pH adjustment of electrolytes, [15] and concentrated electrolytes. [16][17][18] All of these methods have complex processing technologies and sacrifice capacitance, so being difficult for practical applications. Recently, Zhu and co-workers

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We design V doped NiCoP nanosheets with P vacancies induced by Ar plasma as a cost-effective and bifunctional electrocatalyst for overall water splitting.

Developing low‐cost and high‐efficiency catalysts for sustainable hydrogen production through electrocatalytic hydrogen evolution reaction (HER) is crucial yet remains challenging. Here, a strategy is proposed to fill Ni‐vacancy (Niv) sites of dual‐deficient NiO (D‐NiO‐Pt) deliberately created by Ar plasma with homogeneously distributed Pt atoms driven by oxygen vacancies (Ov). The incorporated Pt atoms filling the Niv reduce the formation energy to increase crystal stability, and subsequently combine with additional Ov to tune the electronic structure of the surrounding Ni sites. Thus, a more ideal hydrogen adsorption free energy (ΔGH*) closer to 0 of Ni sites and Pt sites can be achieved. As a result, the D‐NiO‐Pt electrode achieves superior mass activity of ≈1600 mA mg−1 (normalized by platinum) and nearly negligible loss of activity during long‐term operation, which is much better than as‐prepared Pt‐containing NiO catalysts without plasma treatment. A low overpotential of 20 mV is required for the D‐NiO‐Pt at 10 mA cm−2 in alkaline HER, outperforming that of the commercial Pt/C. In addition, the universal access to the other Ni‐based compounds including nickel phosphide (Ni2P), nickel sulfide (Ni0.96S), and nickel selenide (NiSe2) is also demonstrated by employing a vacancy‐driven Pt filling mechanism.

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To realize high-performance and long life span supercapacitors, highly electrochemically active materials and rational design of structure are highly desirable.

We report a facile synthesis strategy for core-branched CoSe2/Ni0.85Se nanotube arrays directly on Ni foam by simply selenizing Co-precursor nanowires.