Role of acid-treated clay minerals in improving electrochemical pseudocapacitance of nickel boride composites

Clay minerals have become a preferred alternative to conventional high-cost electrode due to their environmental sustainability and cost-effectiveness. However, their constrained active sites and specific surface area constrain their practical applications. The modification treatment has been shown to effectively regulate the specific surface area, porosity, and number of active sites of the material. In this work, the etching of clay minerals was achieved through the utilization of varying concentrations of strong and weak acids. In this work, we investigated the effects of strong and weak acid etching at different concentrations on the electrochemical performance of Ni₃B composites with various clay minerals (montmorillonite, vermiculite, halloysite, sepiolite, talc) after liquid-phase reduction. Results indicate that moderate acid etching increases specific surface area and exposes more active sites, promoting Ni₃B dispersion and enhancing pseudocapacitive performance. Among the composites, vermiculite etched with 3 M H₂SO₄ (3eVermiculite@Ni₃B) exhibited the best performance, demonstrating a high specific capacitance of 1430 F g −1 at a current density of 0.5 A g −1 and excellent cycling stability (85.64% capacity retention after 3000 cycles at the current density of 1 A g −1 ). The assembled asymmetric supercapacitor (3eVermiculite@Ni₃B//AC) achieved a high energy density of 93.85 W h kg −1 at a power density of 374.99 W kg −1 , demonstrating the application potential of acid-etched clay minerals in advanced energy storage systems.