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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 corrosive anions (e.g., Cl−) have been recognized as the origins to cause severe corrosion of anode during seawater electrolysis, while in experiments it is found that natural seawater (~0.41 M Cl−) is usually more corrosive than simulated seawater (~0.5 M Cl−). Here we elucidate that besides Cl−, Br− in seawater is even more harmful to Ni-based anodes because of the inferior corrosion resistance and faster corrosion kinetics in bromide than in chloride. Experimental and simulated results reveal that Cl− corrodes locally to form narrow-deep pits while Br− etches extensively to generate shallow-wide pits, which can be attributed to the fast diffusion kinetics of Cl− and the lower reaction energy of Br− in the passivation layer. Additionally, for the Ni-based electrodes with catalysts (e.g., NiFe-LDH) loading on the surface, Br− causes extensive spalling of the catalyst layer, resulting in rapid performance degradation. This work clearly points out that, in addition to anti-Cl− corrosion, designing anti-Br− corrosion anodes is even more crucial for future application of seawater electrolysis. It is known that chloride anions cause severe anode corrosion during seawater electrolysis. Here we found that bromide in seawater is even more harmful to Ni-based anodes, causing the spalling of the catalyst layer and the formation of shallow-wide pits on the substrate, leading to performance degradation. [ABSTRACT FROM AUTHOR]

Seawater electrolysis to produce hydrogen is a critical technology in marine energy projects; however, the severe anode corrosion caused by the highly concentrated chloride is a key issue should be addressed. In this work, we discover that the addition of sulfate in electrolyte can effectively retard the corrosion of chloride ions to the anode. We take nickel foam as the example and observe that the addition of sulfate can greatly improve the corrosion resistance, resulting in prolonged operating stability. Theoretical simulations and in situ experiments both demonstrate that sulfate anions can be preferentially adsorbed on anode surface to form a negative charge layer, which repulses the chloride ions away from the anode by electrostatic repulsion. The repulsive effect of the adsorbed sulfate is also applicable in highly‐active catalyst (nickel iron layered double hydroxide) on nickel foam, which shows ca. 5 times stability of that in traditional electrolyte. [ABSTRACT FROM AUTHOR]

The combination of solid oxide electrolysis cells (SOECs) with renewable electricity has enormous potential, but this requires the cells to be able to adapt to strong fluctuation conditions. This work directly combines fluctuating actual wind power with flat-tube Ni-YSZ/YSZ/LSCF-GDC SOECs to study the operational stability and energy consumption under wide fluctuation and constant current electrolysis. The results indicate that under an average electrolysis current density of 0.26 A cm−2, there is little difference in stability between fluctuation and constant current electrolysis. At a high current density of 0.58 A cm−2, the cells operating for 375 h under fluctuation conditions exhibit a larger degradation rate. The current density is dynamically switched between 0 and 0.93 A cm−2 to simulate actual wind turbine power fluctuations from 0 to 100 %. After rapid large-scale current switches for 2000 times in 375 h, little change is observed in the cell structure. Under fluctuating electrolysis, the minimum energy consumption for power-to-gas conversion in SOEC is 2.84 kWh/Nm3, while under constant current electrolysis, the lowest energy consumption is 2.67 kWh/Nm3. In summary, SOECs can efficiently and stably consume and store highly fluctuating renewable power and can also dynamically respond to wide power ranges from 0 to 100 %. • 100 % long-term actual wind power storage was simulated using SOEC. • 2000 rapid large-scale switches did not significantly damage the cell. • Energy consumption of 2.84 kWh/Nm3 was obtained in fluctuation steam electrolysis. • Degradation under fluctuation was significantly higher than constant in high current. [ABSTRACT FROM AUTHOR]

• Seawater without any treatment was directly used for hydrogen production. • High energy conversion efficiency and long-term stability were obtained. • The cell did not show any obvious change after operation for 400 h. Hydrogen production from seawater electrolysis provides a basis for clean and sustainable development of our energy system. However, in the existing seawater splitting techniques, it is difficult to overcome the damage to electrolyzers by the sea salt. In this work, solid oxide electrolysis was used to split untreated seawater, and its electrochemical performance and long-term stability were studied. The electrolysis was carried out at constant current density of 200 mA/cm−2 for 420 hrs with 183 mL/min hydrogen production and a degradation rate of 4.0%. Energy conversion efficiency of 72.47% was obtained even without reusing the high temperature exhaust gas. After 420 hrs of experiment, it was found that the structure and composition of the cell remained unchanged, showed that long-term operation had no obvious effect on the cell itself. This work shows that the performances of solid oxide electrolysis cell in seawater splitting are excellent, and provides a good choice for energy storage and hydrogen production from seawater. [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]