Developing exceedingly efficient, cost-effective, and environmentally friendly bifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) especially at high current density is crucial for realizing the industrial application of electrocatalytic overall water splitting. In this work, non-noble-metal bifunctional catalysts with single Ni atoms, single Fe atoms, and NiFe nanoalloys supported on carbon nanotubes (Ni SA Fe SA -Ni x Fe/CNT) are rationally designed and fabricated. In 1 M KOH, the optimized Ni SA Fe SA -Ni 50 Fe/CNT catalyst affords low overpotentials of 64 and 227 mV at 10 mA cm −2 for catalyzing the HER and OER, respectively. Moreover, the catalyst enables the overall water splitting at a low cell voltage of 1.49 V to achieve 10 mA cm −2 in 1 M KOH. At a cell voltage of 1.80 V, the current density is as high as 382 mA cm −2 , which surpasses those of most materials reported so far. After a simple two-step oxidation and rereduction procedure, the catalytic performances of the OER, HER, and overall water splitting recover completely to their original levels. This work not only provides a potential catalyst candidate for economically realizing water splitting but also shows a method for reactivatable catalyst design.

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High‐entropy‐alloy nanoparticles (HEA‐NPs) have attracted great attention because of their unique complex compositions and tailorable properties. Further expanding the compositional space is of great significance for enriching the material library. Here, a step‐alloying strategy is developed to synthesis HEA‐NPs containing a range of strongly repellent elements (e.g., Bi–W) by using the rich‐Pt cores formed during the first liquid phase reaction as the seed of the second thermal diffusion. Remarkably, the representative HEA‐NPs‐(14) with up to 14 elements exhibits extremely excellent multifunctional electrocatalytic performance for pH‐universal hydrogen evolution reaction (HER), alkaline methanol oxidation reaction (MOR), and oxygen reduction reaction (ORR). Briefly, HEA‐NPs‐(14) only requires the ultralow overpotentials of 11 and 18 mV to deliver 10 mA cm−2 and exhibits ultralong durability for 400 and 264 h under 100 mA cm−2 in 0.5 m H2SO4 and 1 m KOH, respectively, which surpasses most advanced pH‐universal HER catalysts. Moreover, HEA‐NPs‐(14) also exhibits an impressive peak current density of 12.6 A mg−1Pt in 1 m KOH + 1 m MeOH and a half‐wave potential of 0.86 V (vs RHE.) in 0.1 m KOH. The work further expands the spectrum of possible metal alloys, which is important for the broad compositional space and future data‐driven material discovery.

Metal sulfides are promising anodes for sodium-ion batteries because of their high theoretical capacities. However, they also suffer from the limitations of poor cycling stability and rate performance caused by volumetric strain. Here, trimetallic hybrid sulfide (Ni, Fe, Co)S x nanocrystals embedded into nitrogen-doped carbon nanocubes are successfully obtained with abundant channels for ion diffusion, high specific surface area for a pseudocapacitive effect, and enough voids to buffer volumetric strain. As anode material for a sodium-ion battery, the hybrid sulfides exhibit highly reversible specific capacity, good rate capability, and cycling performance. Such mixed-metal sulfides with novel physical or chemical properties may also be extended to other emerging fields.

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