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Hydrogen production from seawater remains challenging due to the deactivation of the hydrogen evolution reaction (HER) electrode under high current density. To overcome the activity-stability trade-offs in transition-metal sulfides, we propose a strategy to engineer sulfur migration by constructing a nickel-cobalt sulfides heterostructure with nitrogen-doped carbon shell encapsulation (CN@NiCoS) electrocatalyst. State-of-the-art ex situ/in situ characterizations and density functional theory calculations reveal the restructuring of the CN@NiCoS interface, clearly identifying dynamic sulfur migration. The NiCoS heterostructure stimulates sulfur migration by creating sulfur vacancies at the Ni3S2-Co9S8 heterointerface, while the migrated sulfur atoms are subsequently captured by the CN shell via strong C-S bond, preventing sulfide dissolution into alkaline electrolyte. Remarkably, the dynamically formed sulfur-doped CN shell and sulfur vacancies pairing sites significantly enhances HER activity by altering the d-band center near Fermi level, resulting in a low overpotential of 4.6 and 8 mV at 10 mA cm−2 in alkaline freshwater and seawater media, and long-term stability up to 1000 h. This work thus provides a guidance for the design of high-performance HER electrocatalyst by engineering interfacial atomic migration. Stable and efficient hydrogen production from seawater remains challenging. Here the authors engineer sulfur migration in NiCoS electrocatalyst via N-doped carbon encapsulation, generating S vacancies and S doped CN active sites at the interface that improves electrocatalytic hydrogen evolution activity and durability in both alkaline freshwater and seawater. [ABSTRACT FROM AUTHOR]

Summary: Aqueous zinc batteries (AZBs) hold great promise for advancing applications in next‐generation energy storage devices because of their high safety, high energy density, and low cost. However, zinc metal anodes have greatly impeded the application in AZBs due to their poor cycle performance. Short lifespan, which is caused by dendritic growth, deformation, corrosion, and competing hydrogen evolution, is very tricky. Herein, a stable Sn@Cu foam, prepared by plating tin on copper foam, is reported as the substrate of Zn anodes. We evaluate the quality of plating tin layers, which are prepared by using different tin salt solutions, and Na2SnO3 solution is eventually selected. Electrochemical tests show that Sn@Cu foam can not only inherit the merits of Cu foam but also suppress hydrogen evolution reaction and lower the initial heterogeneous nucleation barrier of deposited Zn. Moreover, in situ observation by optical microscope demonstrates that Zn dendrite growth on Sn layer is suppressed during the plating‐stripping process. As a result, a compact Zn layer on Sn@Cu foam is obtained (Zn/Sn@Cu foam), symmetrical cells display superior cycling life of 1800 h at 1 mA cm−2 for 1 mAh cm−2, and full cells with VO2 cathode deliver remarkably better cycling stability and longer lifespan. [ABSTRACT FROM AUTHOR]

Abstract: Insights into the relationship between the crystal planes of metal oxides and the catalytic activity of the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) are essential for developing efficient renewable energy technologies. Herein, spinel Co3O4 nanomaterials were synthesized controllably with the specified morphologies of nanocubes, nanosheets, and nanoplates with different exposed planes of {100}, {110}, and {111}, respectively. The effects of the crystal planes of Co3O4 on the activity for the OER, ORR, and HER were subsequently investigated in alkaline media. Different electrocatalytic performances are possibly attributed to the abundance ratios of Co3+/Co2+ over the different exposed planes. The surface Co3+ ions exhibit higher activity for the OER and HER, whereas the surface Co2+ ions exhibit better performance for the ORR; moreover, higher electroconductivity enhances the polarization current for ORR and HER except OER. [ABSTRACT FROM AUTHOR]

Studying the electrode activity and stability changes caused by the increasing ion concentration during the alkaline seawater electrolysis is crucial to exploit industrial-level seawater electrolyser. Herein, the concentration of hydroxide ion (OH−), chlorine ion (Cl−), and the other ions in alkaline seawater (OIAS) is investigated to understand the activity and stability for nickel foam (NF) electrodes as both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrodes. As a whole, the activity of HER electrode is mainly dropped with the increasing concentration of OH−, while the OER electrode is enhanced with the increasing concentration of OH− and Cl−. However, the all (OH−, Cl− and OIAS) increasing ion concentrations decrease the HER electrode stability, while the Cl− reduces, the OH− and OIAS enhances the stability of OER electrode. Moreover, the chloride evolution reaction (ClER) in 6 M NaOH with seawater can be ignored even though the concentration of salts in alkaline seawater reach to saturation. • The trends of activity and stability of HER and OER electrode changed with ion concentrations increasing. • The reasons for activity and stability changes with the increasing ion concentration. • The suggestions for alkaline seawater electrolysis operation. [ABSTRACT FROM AUTHOR]

In this work, a high-specific-energy magnesium/water battery (Mg/H 2 O battery) combining Mg oxidation with hydrogen evolution reaction (HER) is developed for full-depth ocean application. With the optimized platinum loading associated with moderate Ni(OH) 2 on nickel foam, the performance can be increased obviously. Coupled with AZ91 Mg alloy anode, the specific energy of Mg/H 2 O battery reaches a dramatic value of 1003 W h kg −1 . Moreover, ultrahigh pressure of 1100 bar in the deep-sea simulated condition brings negligible effects on the performance of battery and electrodes. The influence of low temperature can be reduced to an acceptable level under the application at low discharge current density. Stable discharge of the battery for 100 days is also obtained. This work provides a new idea to supply power source with high specific energy, excellent environment adaptability, good safety and low cost for underwater application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg anode in NaAc electrolyte exhibits uniform dissolution behavior. • Sufficiently inhibit the anodic hydrogen evolution corrosion of Mg anode. • Enhance the utilization efficiency of Mg anode up to 84% at 10 mA cm−2. • NaAc electrolyte is applied in a commercial Mg air battery. • Verify the anodic corrosion of Mg is related to its localized passive film rupture. Aqueous magnesium air batteries are promising energy conversion devices because of high theoretical energy density, inherent safety and low cost. However, their practical energy density is significantly limited due to the dramatic hydrogen evolution corrosion of Mg anode in conventional sodium chloride (NaCl) electrolyte. Herein, we suppress the hydrogen evolution reaction on the surface of Mg anode using sodium acetate (NaAc) electrolyte, in which Mg anode exhibits uniform anodic dissolution behavior without the notorious localized corrosion. It is demonstrated that acetate ion (Ac-) averts the localized passive film breakdown of Mg anode in virtue of its large diffusion energy barrier within the film. Therefore, the anodic hydrogen evolution phenomenon amid discharge is evidently repressed. This enables Mg anode to achieve a high utilization efficiency of 84 % at 10 mA cm−2 compared with 59 % in NaCl electrolyte. Mg air battery tests manifest that its specific energy based on the anode weight is boosted from 1370 to 1770 Wh kg−1. Finally, the practicality of NaAc electrolyte is confirmed in a commercial Mg air battery. This work provides a simple and scalable solution for high performance Mg air battery. [ABSTRACT FROM AUTHOR]

• The doping of Mn exposes more Co3+ active sites to enhance the ORR/OER activity. • The particle size of Mn-Co 3 O 4 nanoparticles was only about 5.5 nm. • Rechargeable ZAB displays a high-power density and superior cycling stability. High-performance and low-cost bifunctional electrocatalysts for ORR and OER are urgently required for rechargeable Zn-air batteries. Herein, a series of Mn-doped Co 3 O 4 nanoparticles grown on carbon nanotubes (Mn-Co 3 O 4 @CNTs) bifunctional electrocatalysts are designed. Owing to the moderate doped Mn atoms, the Mn-Co 3 O 4 heightens ORR activity via the synergistic effect between Co and Mn atoms, and more Co3+ active sites are exposed on the surface of Mn-Co 3 O 4 to enhance the OER rate. As a result, the 40% Mn-doped Mn-Co 3 O 4 @CNTs electrocatalyst exhibits higher ORR (E 1/2 = 0.84 V) and OER (η 10 = 356 mV at 10 mA cm−2) performance. More significantly, the Mn-Co 3 O 4 @CNTs equipped with rechargeable ZAB displays a high power density of 116 mW cm−2, a low charge-discharge voltage gap of 0.94 V at 10 mA cm−2, and superior cycling stability of over 425 h and 1200 cycles, being much more outperforming than Pt- and Ru-based ZABs. [Display omitted] [ABSTRACT FROM AUTHOR]

• Porous Ni(OH) 2 membrane resists phosphate but transfers OH− and H 2 • Phosphate ions directly participate in HER as reactant on Pt and Ni electrode • Phosphate ions enhance HER activity of Pt but lower HER activity for Ni electrode Phosphate buffer solution (PBS) is widely used in hydrogen evolution reaction (HER), however, the HER mechanism in PBS is still unclear whether the phosphate directly react with electrode like H 2 O. Herein, the porous and defective Ni(OH) 2 permselective membrane covered Pt and Ni electrode was fabricated by the electrodeposition method to identify the reaction mechanism. By obviously rejecting the phosphate and almost unimpededly transferring the OH−, H 2 O and H 2 , the membrane averts the contact of phosphate with the electrode surface without impeding of the necessary mass transfer of HER. Combining electrochemical analysis and theoretical calculation, the phosphate is found to be the HER reactant of Pt and Ni electrode in PBS. Detailly, the phosphate competes with H 2 O and accelerates the HER for Pt electrode, while poisons Ni electrode to deteriorate the HER performance. The Ni(OH) 2 membrane covered on HER electrode obviously rejects the transfer of phosphate, but almost unimpededly transfer the OH−, H 2 O and H 2 depending on the porous structure. These unique permselective feature helps to identify the HER mechanism in phosphate buffer solution. [Display omitted] [ABSTRACT FROM AUTHOR]