CuNiFe Alloy‐Modified MWCNTs Derived from Waste Battery Leachate for Enhanced Photocatalytic H₂ Evolution Over ZnIn₂S₄

Abstract The application of ZnIn 2 S 4 (ZIS) in photocatalytic water splitting is hindered by rapid charge carrier recombination and photocorrosion. To address these challenges, this study introduces multi‐walled carbon nanotubes (MWCNTs) as a dual‐functional platform for enhancing ZIS performance. First, MWCNTs are activated for efficient adsorption of metal ions from waste battery leachate, followed by hydrogen reduction method to construct highly dispersed CuNiFe multi‐metallic alloys as co‐catalysts. Second, ZIS is grown in situ on the MWCNTs through a one‐step synthesis process. The conductive MWCNTs facilitate efficient charge transfer and suppress photocorrosion, while the CuNiFe alloy co‐catalysts further improve catalytic activity. The optimized M‐C‐ZIS composite achieves a hydrogen evolution rate of 327.6 µmol h −1 , 4.47 times higher than pristine ZIS, with excellent stability over multiple cycles. This work demonstrates the dual functionality of MWCNTs as both an ion adsorbent and a conductive medium, bridging resource recovery and photocatalysis. It provides a scalable and cost‐effective strategy for developing noble‐metal‐free photocatalysts with high efficiency and stability, paving the way for sustainable hydrogen production