Membrane-free two-step water electrolysis enabled by a stable organic redox mediator

, just 3.12 s), and exceptional cyclability over 30 000 cycles. More importantly, two-step water electrolysis under high P-ACD loading achieves a remarkable coulombic efficiency of nearly 100% even after 600 consecutive cycles, whilst concurrently exhibiting favorable cycle stability for hydrogen production that surpasses 184 h. Consequently, this system provides a new avenue for achieving operational flexibility and membrane-free hydrogen production.