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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 Ni 3 S 2 -Co 9 S 8 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., (© 2024. The Author(s).)

In seawater, severe hydroxide-based precipitation on the hydrogen evolution reaction (HER) electrode surface is still a major stumbling block for direct seawater electrolysis. Here, we design a direct seawater HER electrode with excellent anti-precipitation performance based on an Ni(OH) 2 nanofiltration membrane in situ grown on nickel foam (NF) at room temperature. The positively charged Ni(OH) 2 membrane with nanometer-scale cracks realises an ion sieving function, which apparently hinders the transfer of Mg 2+ /Ca 2+ ions to suppress precipitation, while rapidly transporting OH - and H 2 O to ensure HER mass transfer. Therefore, the Ni(OH) 2 -membrane-decorated seawater HER electrode reduces precipitation by about 98.3% and exhibits high activity and stability. Moreover, in the application of a direct seawater electrolyser and magnesium seawater battery, the Ni(OH) 2 membrane-decorated electrode also shows low precipitation and high stability. This work highlights a potential strategy to solve HER electrode precipitation in seawater via an ingenious electrode structure design., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Integrating femtosecond lasers with electron microscopies has enabled direct imaging of transient structures and morphologies of materials in real time and space. Here, we report the development of a laser-free ultrafast electron microscopy (UEM) offering the same capability but without requiring femtosecond lasers and intricate instrumental modifications. We create picosecond electron pulses for probing dynamic events by chopping a continuous beam with a radio frequency (RF)-driven pulser with the pulse repetition rate tunable from 100 MHz to 12 GHz. As a first application, we studied gigahertz electromagnetic wave propagation dynamics in an interdigitated comb structure. We reveal, on nanometer space and picosecond time scales, the transient oscillating electromagnetic field around the tines of the combs with time-resolved polarization, amplitude, and local field enhancement. This study demonstrates the feasibility of laser-free UEM in real-space visualization of dynamics for many research fields, especially the electrodynamics in devices associated with information processing technology., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Rational electrode design is crucial to promote the performance of the hydrogen evolution reaction (HER) via further enhancing the activity, stability, and utilization of platinum (Pt) in an alkaline electrolyte. Herein, a binder-free low-Pt-content HER electrode, Pt (∼20 μg cm -2 ) decorated on nickel hydroxide grown on nickel foam (Pt-Ni(OH) 2 -2h-NF20), is fabricated at near room temperature in a test tube. To lower the ohmic resistance, for the first time, the Pt nanoparticles were location-selectively anchored on the bottom of height-controlled vertical Ni(OH) 2 nanosheets via utilizing the mass transfer resistance of the dense Ni(OH) 2 film for chloroplatinate. Furthermore, the excellent mass transfer, high specific surface area of Pt, synergistic effect between Pt with Ni(OH) 2 , and stable structure together prompt the resulting electrode with a special structure to exhibit superior HER electrocatalytic activity and stability in 1 M KOH. Typically, this electrode reaches a current density of 35.9 mA cm -2 at an overpotential of 100 mV, which is over 8 times higher than that of commercial Pt/C, and the overpotential only increases by 20 mV at 100 mA cm -2 over 150,000 s of stability test. Benefiting from the simple fabrication process, the electrode with an area of 840 cm 2 was successfully prepared with a steady overpotential of 370 mV at 1000 mA cm -2 and increased potential of 23 mV over 50 h of stability test.

The diamond amplifier (DA) is a new device for generating high-current, high-brightness electron beams. Our transmission-mode tests show that, with single-crystal, high-purity diamonds, the peak current density is greater than 400  mA/mm², while its average density can be more than 100  mA/mm². The gain of the primary electrons easily exceeds 200, and is independent of their density within the practical range of DA applications. We observed the electron emission. The maximum emission gain measured was 40, and the bunch charge was 50  pC/0.5  mm². There was a 35% probability of the emission of an electron from the hydrogenated surface in our tests. We identified a mechanism of slow charging of the diamond due to thermal ionization of surface states that cancels the applied field within it. We also demonstrated that a hydrogenated diamond is extremely robust.