Surface reconstruction of high-entropy FeCoNiCrMn: exploring oxygen-activated amorphous/crystalline heterostructure for robust H2 generation

Transition metal-based electrocatalysts with desirable surface oxophilicity and robust substrate adhesion can greatly lower the water dissociation barrier and enhance hydrogen evolution reaction (HER) activity. Among several candidates, FeCoNiCrMn high-entropy alloy (HEA) with its high corrosion resistance and tunable electronic structure has been regarded as particularly promising for water splitting. In this work, it is shown that artificial surface reconstruction of FeCoNiCrMn electrodes (HEA) that are activated via high-temperature oxidation can regulate the formation of Co-Mn-Fe amorphous layers (HEA/O 2 ) with high mechanical stability. We designed an amorphous/crystalline heterostructure consisting of amorphous Co-Mn-Fe nanosheets and an FeCoNiCrMn substrate that is able to modulate electron redistribution. This electronic modulation facilitates substantial charge transfer during the HER. Consequently, the obtained HEA/O 2 electrode exhibits a low overpotential driven electrocatalysis for HER in alkaline condition: 137.9 mV at 10 mA cm − 2 and 275.7 mV at 500 mA cm − 2 , respectively. Remarkably, the electrode also maintains stable HER performance for 500 h at 500 mA cm − 2 . Even in simulated seawater, the HEA/O 2 electrode exhibits extraordinary stability with negligible activity decay for 500 h. This study demonstrates a novel strategy to drive the self-formation of active/passive layers on transition metal-based electrodes for stable and efficient HER.