Cobalt-Intercalated Natural Montmorillonite Clay as a Multifunctional Platform for Alkaline Water Splitting and...

Montmorillonite (MMT), a layered silicate mineral is a promising potential catalytic support for water splitting and supercapacitor applications because of its large surface area, affordability, thermal stability, and ion exchange capacity. In this study, we introduce MMT clay modified with different weight percentages of Co (3, 5, 10, and 15wt%) that modulate the alumina-silica framework. Tandemly, it facilitates the stacked layers of clay and generates numerous active sites. The Co-MMT5 exhibited excellent HER and OER performance at an overpotential of 153 mV (at 20 mAcm^-2) and 347 mV (at 10 mAcm^-2), respectively. Moreover, we assessed overall water splitting with the Co-MMT5 catalyst, which required a cell potential of 1.73 V to achieve 10 mAcm^-2 of current density. Beyond catalysis, Co-MMT5 also functions as a high-performance pseudocapacitive electrode, delivering a specific capacitance of 330 F/ g at 1 A/g, driven by reversible Co²⁺/Co³⁺ redox reactions within the clay matrix. The shared cobalt redox chemistry underlying both electrocatalysis and charge storage provides a unified mechanistic origin for the multifunctionality of this material. This work establishes cobalt-intercalated natural clay as a scalable and sustainable materials platform for integrated hydrogen production and electrochemical energy storage.