Probing Under‐Utilized Melem as Host Scaffold with Strategic Modulation of Cobalt Oxidation State to Accelerate Alkaline Water Splitting

Abstract The potential of cobalt catalysts for sustainable, carbon‐neutral hydrogen production through water splitting can be fully achieved by fundamental understanding‐driven strategic tuning of metal oxidation states on a uniform scaffold. In pursuit of a stable scaffold that can enhance electrocatalytic activity through metal‐N synergism and envisaging that g‐C₃N₄ has inherited its properties from its structurally distinct predecessor, Melem; a comprehensive exploration of s‐heptazine (Melem, M) is furnished as host for strategic tuning of cobalt electrocatalysts having variable oxidation states. Co(II)‐doped heptazine (Co^II@M) catalyzed oxygen evolution reaction (OER) with an overpotential of 302 mV achieving 50 mA cm⁻² current density, with minimal charge‐transfer resistance (0.41 Ω). Co(0)‐doped heptazine nanotube (Co⁰@M) facilitated the arduous H‐O‐H bond cleavage for alkaline hydrogen evolution reaction (HER), achieving 50 mA cm⁻² current density at 206 mV overpotential, with low charge‐transfer resistance of 0.66 Ω, attesting to the scaffold's assistance to electron transfer. The Co^II@M||Co⁰@M assembly shows low cell voltage (1.637 V @ 10 mA cm⁻²) and promising stability (114 h) for total water splitting. s‐heptazine scaffold ensured finer dispersion and stabilization of cobalt active sites in a corrosive environment. The scaffold's substantial stability, attributes to its nitrogen‐rich core and extensive H‐bonding, unlocks the potential of under‐explored melem‐based systems for electrocatalytic applications.