Self-Reconstructing Cobalt Hydroxide on Graphite: A Binder-Free Electrode for Alkaline Oxygen Evolution

Binder-free oxygen evolution electrodes with strong catalyst-support integration are important for practical alkaline water electrolysis. Here, a cobalt hydroxide catalytic layer was grown directly on graphite through a simple open-vessel aqueous deposition route exploiting the evolving air-liquid interface during solvent evaporation. During solvent evaporation, the receding solution level establishes a moving meniscus that confines nucleation along the waterline, producing a spatially defined cobalt hydroxide band without polymer binders, surfactants, or high-pressure processing. This establishes growth environment as an independent design variable, one that governs catalyst placement and substrate coupling without compositional modification. Scanning electron microscopy reveals a platelet-dominated nanosheet morphology characteristic of the brucite-type cobalt hydroxide framework, forming a mechanically integrated catalytic layer directly on the conductive graphite substrate. In 1.0 M KOH, the electrode reaches 10 mA cm -2 at an overpotential of 339.9 mV, with an onset potential of 1.459 V vs RHE and a Tafel slope of 75.55 mV dec -1 indicating a functional electrode-electrolyte interface, and chronopotentiometry at 10 mA cm -2 over 24 h confirms stable operation. Raman spectroscopy on the intact electrode surface confirms the deposited phase as β-Co(OH) 2 and reveals partial Co(OH) 2 →CoOOH surface reconstruction after OER operation. Sequential cyclic voltammetry over 20 cycles shows a brief initial dip followed by progressive activation to a stable plateau by cycle 16, and a repeat polarization curve recorded after activation confirms this improvement directly, with the overpotential at 10 mA cm⁻² decreasing from 339.9 to 313 mV. A drop-cast control electrode of matched catalyst loading, evaluated to isolate the contribution of the electrode architecture, shows a consistently higher overpotential, Tafel slope, and charge-transfer resistance, together with net degradation rather than improvement over 24 h. X-ray photoelectron spectroscopy corroborates this at the surface level, showing substantially greater Co²⁺-to-Co³⁺ conversion on the directly grown electrode after operation and confirming its binder-free composition. These results demonstrate that evaporation-front-mediated deposition is a viable, single-step strategy for fabricating directly integrated binder-free cobalt hydroxide electrodes with effective interfacial charge-transfer characteristics and electrochemical activation behaviour governed by interfacial reconstruction dynamics.