The development of cost-effective, high-performance alkaline hydrogen evolution reaction (HER) catalysts is critical for advancing green hydrogen production. Although noble-metal-based high-entropy alloys (HEAs) show promise, their intrinsic activity and scalability remain constrained by particle size, elemental synergy, and scalable synthesis methods. Here, we present a general, facile and scalable impregnation method to synthesize quaternary medium-entropy alloys (MEAs) as well as quinary and senary high-entropy alloys (HEAs). The gram-scale production of high-performance senary HEA is first reported. The average size is less than 2.0 nm. It only required overpotentials of 4.9/149.3 mV to achieve current densities of 10/1000 mA·cm^–2 with an ultralow noble metal loading of 0.12 mg·cm^–2. Its Pt mass activity at –10 mV overpotential is 0.652 A·mg^–1, 13.4-fold higher than commercial Pt/C. Remarkably, it endures over 100 h at 1 A·cm^–² with negligible degradation. Systematic spectroscopic investigations indicate the importance of an optimal electronic modulation via appropriate alloying to enhance the catalytic activity. Density functional theory (DFT) calculations reveal that optimized synergistic interactions among multi-principal elements reduce the hydrogen-adsorption free energy, enhancing intrinsic HER activity. This work not only establishes a scalable pathway for synthesizing high-performance HEAs but also provides new mechanistic insights into electronic-modulating strategy, opening a new avenue to cost-efficient, industrially viable electrocatalysts for green hydrogen production.

Effective electrochemical conversion of CO₂ to value-added liquid multi-carbon products driven by renewable energy is a promising approach to alleviate excessive CO₂ emission and achieve large-scale renewable energy storage. However, the selectivity and catalytic activity towards liquid multi-carbon products of CO₂ electroreduction reaction are still unsatisfactory due to the sluggish C–C coupling process and the formation of complex oxygen-containing intermediates. Hence, designing and fabricating highly effective electrocatalysts is crucial for practical applications in this field. Here, we developed Cl-modified Cu catalyst (Cu-Cl) for efficient electrochemical reduction of CO₂ to ethanol. The optimal Faradaic efficiency and partial current density of ethanol on the Cu-Cl sample reached 26.2% and 343.2 mA·cm⁻² at −0.74 V (vs. reversible hydrogen electrode (RHE)), which were 1.66 and 1.76 times higher than those of the catalyst without Cl decoration, outperforming those in most previously reported works. Density functional theory (DFT) calculations revealed that the Cl-modified Cu surface suppressed the parasitic hydrogen evolution reaction (HER) and reduced the energy barrier for the C–C coupling process, making the formation of key intermediates favorable for ethanol production. Thus, the decoration of Cl on the Cu surface facilitated ethanol formation.