Long‐Range Conductive Pathways Boost High‐Performance Polymer‐Based Composite for Decoupled Water Electrolysis

Abstract Renewable‐energy‐driven electrolysis for green hydrogen production is pivotal to sustainable energy strategies. However, conventional water electrolysis systems suffer from gas crossover risk due to the simultaneous hydrogen and oxygen evolution. Here, a polymer/carbon nanotube composite (PCNT) is designed and synthesized as a solid‐state redox mediator to decouple H 2 and O 2 production in acidic water electrolysis. Owing to the strong π–π interactions between polymer and carbon nanotubes and the long‐range conductive architectures, the PCNT electrode delivers outstanding rate capability (137 mAh g −1 at 100 A g −1 ) and excellent cycling stability (76% capacity retention after 25 000 cycles at 10 A g −1 ). When combined with photovoltaic panel, the system can decouple the H 2 and O 2 production at different times without a membrane, realizing direct conversion of renewable energy into high‐purity hydrogen.