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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]

Transition metal layered double hydroxides, especially nickel‐iron layered double hydroxide (NiFe‐LDH) shows significant advancement as efficient oxygen evolution reaction (OER) electrocatalyst but also plays a momentous role as a precursor for NiFe‐based hydrogen evolution reaction (HER) catalysts. Herein, a simple strategy for developing Ni‐Fe‐derivative electrocatalysts via phase evolution of NiFe‐LDH under controllable annealing temperatures in an argon atmosphere is reported. The optimized catalyst annealed at 340 oC (denoted NiO/FeNi3) exhibits superior HER properties with an ultralow overpotential of 16 mV@10 mA cm−2. Density functional theory simulation and in situ Raman analyses reveal that the excellent HER properties of the NiO/FeNi3 can be attributed to the strong electronic interaction at the interface of the metallic FeNi3 and semiconducting NiO, which optimizes the H2O and H adsorption energies for efficient HER and OER catalytic processes. This work will provide rational insights into the subsequent development of related HER electrocatalysts and other corresponding compounds via LDH‐based precursors. [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]

Flexible carbon fiber cloth (CFC) is an important scaffold and/or current collector for active materials in the development of flexible self‐supportive electrode materials (SSEMs), especially in lithium‐ion batteries. However, during the intercalation of Li ions into the matrix of CFC (below 0.5 V vs. Li/Li+), the incompatibility in the capacity of the CFC, when used directly as an anode material or as a current collector for active materials, leads to difficulty in the estimation of its actual contribution. To address this issue, we prepared Ni5P4 nanosheets on CFC (denoted CFC@Ni5P4) and investigated the contribution of CFC in the CFC@Ni5P4 by comparing to the powder Ni5P4 nanosheets traditionally coated on a copper foil (CuF) (denoted P‐Ni5P4). At a current density of 0.4 mA cm−2, the as‐prepared CFC@Ni5P4 showed an areal capacity of 7.38 mAh cm−2, which is significantly higher than that of the P‐Ni5P4 electrode. More importantly, theoretical studies revealed that the CFC has a high Li adsorption energy that contributes to the low Li‐ion diffusion energy barrier of the Ni5P4 due to the strong interaction between the CFC and Ni5P4, leading to the superior Li‐ion storage performance of the CFC@Ni5P4 over the pristine Ni5P4 sample. This present work unveils the underlying mechanism leading to the achievement of high performance in SSEMs. [ABSTRACT FROM AUTHOR]

Photoelectrochemical water splitting based on nanostructured bismuth vanadate (BiVO4) can be a promising strategy to produce low‐cost and green H2 to replace fossil fuels and realize carbon neutrality. Herein, a simple chemical way to realize in situ carbon doping into BiVO4 crystalline structure is designed and obtained carbon‐doped BiVO4, namely C‐BiVO4, can improve the electronic conductivity of BiVO4. In addition, the introduction of the synthesized carbon quantum dots (CQDs) as a co‐catalyst, immobilizes CQDs onto the C‐BiVO4 nanosheet and acquires the optimized C‐BiVO4/CQDs heterogeneous structure, which not only boosts light absorption, but also enhances the separation and transfer of the photo‐generated charges. Stemming from the dual carbon actions, the as‐prepared C‐BiVO4/CQDs photoanode exhibits an excellent photocurrent density of 4.83 mA cm−2 at 1.23 V versus the RHE without the use of any hole scavengers. To assure the practical application of the sensitive photocatalyst, a polyaniline layer is electroplated onto the C‐BiVO4/CQDs catalyst as a conducting, electroactive, and protective layer to sustain a remarkable long‐term photocurrent density of 2.75 mA cm−2 for 9 hours. This work suggests that the proposed low‐cost, environmentally friendly dual carbon actions can modify photocatalyst and achieve green production of H2. [ABSTRACT FROM AUTHOR]

Interfacial engineering and electronic modulation are some of the main components for enhancing the catalytic activity of electrocatalysts towards achieving efficient water splitting. Iron nitrides exhibit mediocre oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) due to their unsuitable d‐band energy level. In this work, we strongly boost the HER and OER catalytic performance of Fe2N for the first time by doping Co and Al, which could not only induce the formation of Fe2N/Fe3N hybrid interface but also tune the d‐band center position. The CoAl−Fe2N/Fe3N nanoparticles display HER and OER overpotential of 145 and 307 mV at 10 mA/cm2. XPS and DFT calculations confirm that tailoring the d‐band center position and interfacial engineering facilitates strong electronic interactions between Fe2N and Fe3N, synergistically optimize the electronic structure, which enriches H and H2O adsorption energy and oxygen‐containing intermediates. An alkaline electrolyzer based on CoAl−Fe2N/Fe3N requires an overall potential of 1.67 V at 10 mA/cm2, demonstrating the use of iron nitrides as a bifunctional electrocatalyst for water splitting activity. [ABSTRACT FROM AUTHOR]

Highlights from the article: Keywords: CO2 reduction reaction; Cu2O nanowires; heterostructures; in situ Raman; intermediates The hybridization of Cu SB 2 sb O/CuO nanowires and Ni nanoparticles improves the adsorption of COOH* intermediates to promote the CO conversion efficiency. CO2 reduction reaction, Cu2O nanowires, heterostructures, in situ Raman, intermediates.