Hierarchical Porous Nonprecious High-entropy Alloys for Ultralow Overpotential in Hydrogen Evolution Reaction.

Water electrolysis is considered the cleanest method for hydrogen production. However, the widespread popularization of water splitting is limited by the high cost and scarce resources of efficient platinum group metals. Hence, it is imperative to develop an economical and high-performance electrocatalyst to improve the efficiency of hydrogen evolution reaction (HER). In this study, a hierarchical porous sandwich structure is fabricated through dealloying FeCoNiCuAl2 Mn high-entropy alloy (HEA). This free-standing electrocatalyst shows outstanding HER performance with a very small overpotential of 9.7 mV at 10 mA cm-2 and a low Tafel slope of 56.9 mV dec-1 in 1 M KOH solution, outperforming commercial Pt/C. Furthermore, this electrocatalytic system recorded excellent reaction stability over 100 h with a constant current density of 100 mA cm-2 . The enhanced electrochemical activity in high-entropy alloys results from the cocktail effect, which is detected by density functional theory (DFT) calculation. Additionally, micron- and nano-sized pores formed during etching boost mass transfer, ensuring sustained electrocatalyst performance even at high current densities. This work provides a new insight for development in the commercial electrocatalysts for water splitting.