Dual-Optimized Medium-Entropy Alloy Heterojunction: Synergistically Enhancing Surface Kinetics and Interfacial Mass Transfer for Hydrazine-Assisted Hydrogen Evolution.

Abstract

To address the prominent "bubble shielding" effect at high current densities during hydrazine oxidation reaction (HzOR) as a replacement for the traditional oxygen evolution reaction (OER), this study successfully designed a medium-entropy heterojunction electrocatalyst (Co0.226Fe0.277Ni0.209Mo0.288/MoS2/CC) featuring discontinuous three-phase contact lines through a topological transformation strategy. The catalyst exhibits unique superwetting properties (superhydrophilic/superaerophobic), significantly enhancing bubble detachment efficiency during gas evolution. In situ microscopic observations reveal that the bubble sizes released from the surface are markedly smaller than those form Pt/C/CC under current densities of 10 and 100 mA cm-2. In addition, the Co0.226Fe0.277Ni0.209Mo0.288/MoS2/CC achieves dual optimization of reaction kinetics and interfacial mass transfer through the synergistic effect of enhanced N2H4 adsorption capacity and reduced H* desorption energy barrier, achieves outstanding bifunctional performance in hydrazine-assisted water electrolysis system, requiring overpotential of only 28 mV for HER and work-potential of -6 mV for HzOR to reach a current density of 10 mA cm-2. Furthermore, a membrane-free overall hydrazine splitting (OHzS) system with Co0.226Fe0.277Ni0.209Mo0.288/MoS2/CC as an electrode requires only 0.247 V to deliver 100 mA cm-2. This work provides novel insights for designing efficient and stable gas-evolving electrocatalysts, contributing significantly to advancing sustainable energy conversion technologies.