Crystalline-amorphous Cu0.81Ni0.19@CoN/Mo2N heterostructure nanosheets for carbon-free flexible Zn-air batteries-driven water electrolysis

Designing carbon-free electrocatalysts that can efficiently drive hydrogen evolution (HER), oxygen evolution (OER), and zinc-air battery (ZAB) reactions in alkaline media remains difficult because of the different kinetic requirements of each process. Herein, we demonstrates a carbon-free crystalline-amorphous (C-A) Cu 0.81 Ni 0.19 @CoN/Mo 2 N heterostructured nanosheets synthesized through a single-step annealing method that simultaneously forms a crystalline alloy core and an amorphous nitride shell. This direct route eliminates carbon supports and avoids multi-stage alloying or nitridation, resulting in tightly coupled C–A interfaces that accelerate charge transfer and stabilize active sites. The catalyst delivers low overpotentials of 43 mV for HER and 297 mV for OER at 10 mA cm −2 , enabling an overall water splitting (OWS) low voltage of 1.56 V. It also maintains excellent durability under harsh electrochemical conditions owing to the absence of carbon, mitigating agglomeration and degradation. Density functional theory calculations reveal that the Cu 0.81 Ni 0.19 /CoN optimizes hydrogen adsorption, while the Cu 0.81 Ni 0.19 /Mo 2 N promotes oxygen intermediate formation. Integrated into a flexible ZAB, the catalyst exhibits a high specific capacity of 811.6 mAh g −1 , a small voltage gap of 1.15 V at 50 mA cm −2 , and 150 h of stable cycling. A self-powered system coupling this flexible ZAB-OWS system further demonstrates the practical viability of this one-step-engineered C–A heterostructure for sustainable energy applications.