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Realizing efficient electrocatalysts is a stepping stone toward achieving high‐performance alkaline water/seawater electrolysis, but remains a crucial challenge. Herein, heterogeneous Mo2N/Ni3Mo3N electrocatalysts on nickel foam (denoted MN‐NMN/NF) that is stable and active for the hydrogen evolution reaction (HER) in both alkaline water/seawater are demonstrated. The optimized MN‐NMN09/NF achieves an ultralow HER overpotential of 11 mV@10 mA cm−2 in 1.0 m KOH electrolyte, which is not only superior to the benchmark Pt/C catalysts but also the best reported ever among NiMo‐based electrocatalysts in an alkaline environment. Successively, the optimized MN‐NMN09/NF electrocatalyst can drive HER current densities of 10 and 500 mA cm−2 using low overpotentials of 9.37 and 123 mV in 1.0 m KOH seawater electrolyte, which remains durable after 120 h long‐term electrolysis at a constant current density of 500 mA cm−2. In situ Raman analysis reveals that the enhanced performance is attributed to the accelerated H2O adsorption and OH dissociation processes on the MN‐NMN surfaces. Theoretical analysis further confirms that rapid H2O adsorption‐dissociation kinetics and H adsorption‐conversion kinetics on the Ni3Mo3N/NiOOH and Ni3Mo3N/MoOx surfaces result in boosted HER capability. This work depicts a significant potential for designing stable and efficient hydrogen production electrocatalysts for both alkaline water and seawater electrolysis. [ABSTRACT FROM AUTHOR]

The exploration of cost‐effective multifunctional electrodes with high activity toward energy storage and conversion systems, such as self‐powered alkaline water electrolysis, is very meaningful, although studies remain quite limited. Herein, a heterogeneous nickel‐molybdenum (NiMo)‐based electrode is fabricated for the first time as a trifunctional electrode for asymmetric supercapacitor (ASC), hydrogen evolution reaction, and oxygen evolution reaction. The trifunctional electrode consists of Ni4Mo and MoO2 (denoted Ni4Mo/MoO2) with hierarchical nanorod heterostructure and abundant heterogeneous nanointerfaces creating sufficient active sites and efficient charge transfer for achieving high performance self‐power electrochemical devices. The ASC consists of the as‐prepared Ni4Mo/MoO2 positive electrode, showing a broad potential window of 1.6 V, and a maximum energy density of 115.6 Wh kg−1, while the alkaline overall water splitting (OWS) assembled using the as‐prepared Ni4Mo/MoO2 as bifunctional catalysts only requires a low cell voltage of 1.48 V to achieve a current density of 10 mA cm−2 in aqueous alkaline electrolyte. Finally, by integrating the Ni4Mo/MoO2‐based ASC and OWS devices, an aqueous self‐powered OWS is assembled, which self‐power the OWS to generate hydrogen gas and oxygen gas, verifying great potential of the as‐prepared Ni4Mo/MoO2 for sustainable and renewable energy storage and conversion system. [ABSTRACT FROM AUTHOR]

A practical and effective approach to increase the energy storage capacity of lithium ion batteries (LIBs) is to boost their areal capacity. Developing thick electrodes is one of the most crucial ways to achieve high areal capacity but limited by sluggish ion/electron transport, poor mechanical stability, and high‐cost manufacturing strategies. Here we address these constraints by engineering a unique hierarchical‐networked 10 mm thick all‐carbon electrode, providing a scalable strategy to produce high areal capacity LIB electrodes. The hierarchical‐networked structure utilizes micrometer‐sized carbon fibers (MCFs) as building blocks, nano‐sized carbon nanotubes (CNTs) as good continuous network with excellent electrical conductivity, and pyrolytic carbon as the binder and active material with excellent storage capacity. The combination of the above features endows our HNT‐MCF/CNT/PC electrode with excellent performance including high reversible capacity of 15.44 mAh cm−2 at 2.0 mA cm−2 and exhibits excellent rate capability of 2.50 mAh cm−2 under 10.0 mA cm−2 current density. The Li‐ion storage mechanism in HNT‐MCF/CNT/PC involves dual‐storage mechanism including intercalation and surface adsorption (pseudocapacitance) confirmed by the cyclic voltammetry and symmetric cell analysis. This work provides insights into the construction of high mechanical stability thick electrode for the next generation high areal capacity LIBs and beyond. [ABSTRACT FROM AUTHOR]