Energy Storage Performance of Geopolymer-Based Structural Capacitors Regulated by H2O2-Induced Pore Structure Evolution

To investigate the effects of H2O2 chemical foaming on the pore structure and overall performance of geopolymer materials, foamed geopolymers were prepared using fly ash (FA) and ground granulated blast furnace slag (GBFS) as the primary raw materials. The foaming behavior was regulated by varying the H2O2 content (1 wt% and 2 wt%) and pre-curing temperature (30, 60, and 90 °C). The effects of foaming parameters on the mechanical properties, electrochemical performance, and microstructural characteristics of the materials were systematically evaluated through compressive strength tests, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS). The results demonstrated that increasing the H2O2 content and pre-curing temperature promoted pore formation and enhanced pore connectivity, resulting in a gradual decrease in compressive strength, while the areal capacitance and ionic conductivity were significantly improved. SEM observations revealed that elevated pre-curing temperatures accelerated pore development, while higher H2O2 content further enlarged pores and promoted pore interconnectivity. FTIR analysis indicated that all specimens exhibited similar characteristic absorption peaks, suggesting that H2O2 foaming did not alter the fundamental gel structure of the geopolymer matrix but primarily affected pore structure evolution. EIS results showed that increasing the foaming degree reduced both the equivalent series resistance and charge transfer resistance, thereby enhancing ion transport capability. These findings demonstrate that pre-curing temperature and H2O2 content jointly regulate pore structure development and the balance between mechanical and electrochemical properties. This study provides valuable insights into the structural design and functional applications of foamed geopolymer materials.