Interfacial Assembly of GO@ZIF-8 Composite for High-Performance Supercapacitors: Mechanistic Insights from Dunn’s Method

The rapid demand for sustainable energy storage materials has drawn significant attention to zeolitic imidazolate framework-8 (ZIF-8). Despite its promise, the intrinsically low electrical conductivity of ZIF-8 restricts efficient charge transport, thereby limiting its overall supercapacitor (SC) performance. To overcome this drawback, ZIF-8 was hybridized with graphene oxide (GO) through an interfacial assembly strategy. The resulting GO@ZIF-8 composite electrode delivered an exceptional specific capacity of 824 F g–1 at 0.5 A g–1, far surpassing that of pristine GO (71.6 F g–1) and ZIF-8 (191 F g–1). When configured into a symmetric supercapacitor (SSC), the optimized composite achieved a capacitance of 372 mF cm–2 at 1.75 mA cm–2, while maintaining 91.1% of its initial capacity over 7000 cycles, underscoring its excellent cycling durability and demonstrating efficient surface utilization and outstanding rate capability. The device also delivered favorable energy and power densities, confirming its practical applicability. The superior electrochemical behavior arises from the synergistic combination of the high surface area and porosity of ZIF-8 with the conductive GO framework, which collectively enhances ion accessibility and charge transfer. Importantly, mechanistic analysis using Dunn’s method revealed that charge storage in the GO@ZIF-8 electrode and SSC involves both diffusion-controlled and capacitive processes, with surface-controlled capacitive reactions becoming predominant at higher scan rates. This balance between bulk ion diffusion and fast surface-confined processes underpins the hybrid material’s high-rate performance, confirming its potential as a high-performance electrode for next-generation SCs.