PVA-based interface engineering of activated porous carbon for enhanced capacitance in aqueous supercapacitors

Activated porous carbon (APC) is widely used as a supercapacitor electrode, yet its practical charge-storage performance is critically dependent on electrolyte access to ion-storage sites at the carbon interface. Conventional strategies for APC-based electrodes mainly focus on increasing specific surface area, tailoring pore structures, or introducing additional active/dielectric components, whereas interfacial accessibility and dynamic charge-storage utilization are less explicitly addressed. Here, we introduce a novel polyvinyl alcohol (PVA)-based post-treatment strategy to ameliorate the capacitance performance of the electrode in aqueous supercapacitors by regulating the electrode-electrolyte interface. The novelty of this work lies in using a hydroxyl-rich PVA interfacial layer to enhance electrolyte accessibility and interfacial charge-storage dynamics without redesigning the carbon framework. Systematic analyses indicate that, despite a reduced specific surface area (SSA) and an increased dielectric response, PVA-coated APC delivers the highest capacitance under otherwise identical conditions. Indeed, such enhancement originates primarily from enhanced infiltration and molecular mobility within the PVA layer, thereby increasing the fraction of electrochemically effective charge-storage sites and enhancing the capacitance of the electrode. The findings reported in this work provide a new strategy for interface engineering of APC-based electrodes for supercapacitors.