2D CaWO4 nanosheets derived from scheelite minerals for enhanced electrocatalysis in oxygen evolution reaction

Scheelite (CaWO4) mineral holds promise as a cost-effective and efficient catalyst for the oxygen evolution reaction (OER) crucial in renewable energy technologies. However, challenges such as limited active site exposure and low electrocatalytic performance need addressing. In this work, we have fabricated two-dimensional (2D) CaWO4 nanosheets from scheelite minerals via a straightforward ultrasonic exfoliation method and evaluated their efficacy as OER catalysts. Compared to scheelite powders, these 2D nanosheets exhibited superior crystallinity and a 1.26-fold increase in electrochemical surface area, promoting active site exposure. The 2D CaWO4 nanosheet electrode demonstrated outstanding OER catalytic performance, achieving a current density of 20 mA/cm2 at an overpotential of 290 mV in alkaline conditions, which was lower than that of bulk CaWO4 electrodes (similar to 340 mV). Density functional theory calculations attributed this enhanced catalytic performance to moderate adsorption of oxygenated intermediates (*OH, *O, and *OOH) on the W sites of 2D CaWO4 nanosheets. In situ electrochemical atomic force microscopy tests also confirmed the catalytic enhancement by 2D CaWO4 nanosheets during OER. These findings demonstrate the potential of affordable and abundant mineral resources in advancing electrochemical catalysts for oxygen evolution, highlighting their broader application in sustainable energy technologies.