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Designing efficient and bifunctional electrocatalysts for water splitting conforms to the concept of energy conservation and emission reduction but remains challenging now. Herein, the fabrication of a heterostructure by anchoring cobalt‐polyoxometalates (Co‐POM) on NiFe layered double hydroxide (NiFe‐LDH) nanoplates in situ on nickel foam (NF) is first reported (Co‐POM@LDH/NF). The surface area, electron transfer ability, and stability of the heterostructure are increased due to the synergistic effect between Co‐POM and NiFe‐LDH. Particularly, Co‐POM@LDH/NF can deliver a current density of 100 mA cm−2 with an overpotential of only 220 mV for hydrogen evolution reaction (HER) and 226 mV for oxygen evolution reaction (OER) in 1.0 m KOH electrolytes. Impressively, the outstanding stability of Co‐POMs in heterostructures is verified by the experimental observations after electrolysis, indicating the successful construction of stable POMs‐based heterogeneous electrocatalysts. More attractively, the electrolyzer composed by Co‐POM@LDH/NF as anode and cathode shows a much lower operating voltage of 1.51 V at the current density of 10 mA cm−2 for overall water splitting. This study provides a feasible and extensible idea for the design of the POM‐based heterostructures. [ABSTRACT FROM AUTHOR]

Water electrolysis is a compelling method for the production of environmentally friendly hydrogen, minimizing carbon emissions. The electrolysis of water heavily relies on an effective and steady oxygen evolution reaction (OER) taking place at the anode. Herein, we introduce a highly promising catalyst for OER called CoSe2@NiFeOOH arrays, which are supported on nickel foam. This catalyst, referred to as CoSe2@NiFeOOH/NF, is fabricated through a two-step process involving the selenidation of a Co-based porous metal organic framework and subsequent electrochemical deposition on nickel foam. The CoSe2@NiFeOOH/NF catalyst demonstrates outstanding activity for the OER in an alkaline electrolyte. It exhibits a low overpotential (η) of 254 mV at 100 mA cm−2, a small Tafel slope of 73 mV dec−1, and excellent high stability. The good performance of CoSe2@NiFeOOH/NF can be attributed to the combination of the high conductivity of the inner layer and the synergistic effect between CoSe2 and NiFeOOH. This study offers an effective method for the fabrication of highly efficient catalysts for an OER. [ABSTRACT FROM AUTHOR]

Electrochemical hydrogen evolution reaction (HER) with cost‐effectiveness, high performance, and repeatable scale‐up production hold promises for large‐scale green hydrogen generation technology. Herein, a convenient method for scaling up Cu2S@NiS@Ni/NiMo electrocatalysts on Cu foam with high geometric area over 100 cm2 is presented. The hybrid electrode exhibits high hydrogen evolution activity with 190 and 250 mV overpotential at 1000 mA cm−2 and superior stability with negligible overpotential loss after over 2000 h at 500 mA cm−2 under steady‐state conditions in both artificial seawater and real seawater. Detailed characterizations and simulations demonstrate that high intrinsic activity resulting from the unique boundary interface, enhance mass transport resulting from superaerophobic nanoarray architecture, and corrosion resistance resulting from polyanion‐rich passivating layers together lead to the outstanding performance. The practicability is also demonstrated in an alkaline seawater electrolyzer coupling with the hybrid electrode and stable commercial anode. [ABSTRACT FROM AUTHOR]

The preparation of a high performance and durability with low-platinum (Pt) loading oxygen reduction catalysts remains a challenge for the practical application of fuel cells. Alloying Pt with a transition metal can greatly improve the activity and durability for oxygen reduction reaction (ORR). In this work, we present a one-pot wet-chemical strategy to controllably synthesize carbon supported sub-5 nm PtNi nanocrystals with a ~3% Pt loading. The as-prepared PtNi/C-200 catalyst with a Pt/Ni atomic ratio of 2:3 shows a high oxygen reduction activity of 0.66 A mgpt−1 and outstanding durability over 10,000 potential cycles in 0.1 M KOH in a half-cell condition. The PtNi/C-200 catalyst exhibits the highest ORR activity, with an onset potential (Eonset) of 0.98 V and a half-wave potential (E1/2) of 0.84 V. The mass activity and specific activity are 3.89 times and 9.16 times those of 5% commercial Pt/C. More importantly, this strategy can be applied to the gram-scale synthesis of high-efficiency electrocatalysts. As a result, this effective synthesis strategy has a significant meaning in practical applications of full cells. [ABSTRACT FROM AUTHOR]

A pine-shaped Pt nanostructured electrode with under-water superaerophobicity for ultrahigh and steady hydrogen evolution reaction (HER) performance is successfully fabricated by a facile and easily scalable electrodeposition technique. Due to the lower bubble adhesive force (11.5 ± 1.2 μN), the higher bubble contact angle (161.3° ± 3.4°) in aqueous solution, and the smaller size of bubbles release for pine-shaped Pt nanostructured electrode, the incomparable under-water superaerophobicity for final repellence of bubbles from submerged surface with ease, is successfully achieved, compared to that for nanosphere electrode and for Pt flat electrode. With the merits of superior under-water superaerophobicity and excellent nanoarray morphology, pine-shaped Pt nanostructured electrode with the ultrahigh electrocatalytic HER performance, excellent durability, no obvious current fluctuation, and dramatically fast current density increase at overpotential range (3.85 mA mV−1, 2.55 and 13.75 times higher than that for nanosphere electrode and for Pt flat electrode, respectively), is obtained, much superior to Pt nanosphere and flat electrodes. The successful introduction of under-water superaerophobicity to in-time repel as-formed H2 bubbles may open up a new pathway for designing more efficient electrocatalysts with potentially practical utilization in the near future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heterogenous electrocatalytic epoxidation of cyclooctene directly using water as oxygen source was achieved. • Co 4 P 2 W 18 shows higher Faradic efficiency (∼36 %) for epoxide than CoPW 11 and other typical electrocatalysts. • The O atom directly transfer from water to adsorbed cyclooctene on the surface of Co 4 P 2 W 18. • The adjacent terminal O to Co site plays key role in adsorption and activation of water and cyclooctene. The electrocatalytic epoxidation directly using water as oxygen source is considered as a sustainable strategy to achieve epoxide production under ambient conditions. However, it is challenging to develop non-noble metal based heterogeneous electrocatalysts for efficient epoxidation with a deep understanding of the structure–activity relationships. In this work, we report a Weakley-polyoxometalate Na 10 [Co 4 (H 2 O) 2 (PW 9 O 34) 2 ] (Co 4 P 2 W 18) with high efficiency toward electrocatalytic epoxidation of cyclooctene via directly transfer oxygen atom from water. A significantly higher faradaic efficiency of cyclooctene oxide was achieved over Co 4 P 2 W 18 than a Keggin type Co substituted polyoxometalate Na 5 [Co(H 2 O)PW 11 O 39 ] (CoPW 11) and some other typical electrocatalysts including RuO 2 , IrO 2 , and Co 3 O 4 in our system. Experimental results and theoretical calculation indicate that the oxygen atom directly transfers from water for the epoxidation of cyclooctene via the cleavage of O−H of pre-adsorbed water as the rate-determined step. Further calculation demonstrates that the water and cyclooctene were adsorbed by Co site and their adjacent terminal oxygen atom during the epoxidation reaction. With the assistance of this terminal oxygen atom for adsorption and as an electron capture center, lower energy barriers for activation of water and cyclooctene are observed on Co 4 P 2 W 18 than on CoPW 11. Our study provides atomic insight into how structure affects catalytic activity, which benefits designing efficient electrocatalysts. [ABSTRACT FROM AUTHOR]

Exploring cheap, efficient and stable electro-catalysts for hydrogen evolution reaction (HER) is a vital technology for seawater splitting development. Herein, we demonstrate that constructing underlying Cu 2 S nanorod arrays is crucial for improving the HER activity of surface Ni catalyst. Electrochemical results reveal that nickel coated Cu 2 S nanoarrays (Cu 2 S@Ni) on copper foam exhibits a preferable HER activity (~500 mA cm−2 at <200 mV overpotential), outperforming Cu 2 O@Ni and pure Ni counterparts. Detailed analyses indicate that the enhanced HER activity of Cu 2 S@Ni can be attributed to Ni–S interaction between surface nickel and underlying Cu 2 S nanorods, which optimizes the adsorption energy of hydrogen on the surface. Moreover, the Cu 2 S@Ni nanoarray electrode shows a remarkable HER stability, highlighting its promising potential in alkaline seawater electrolysis. • Enhanced HER performance by Ni–S interaction. • Core-shell Cu 2 S@Ni nanorod arrays for alkaline seawater. • Preferable HER activity: ~500 mA/cm2 at <200 mV overpotential. • Favorable durability in alkaline seawater for hydrogen evolution. • Optimization of hydrogen adsorption energy on nickel. [ABSTRACT FROM AUTHOR]