Low-Humidity Sorption Thermal Storage Enhancement via Activated Carbon Oxidative Modification: from Light Experiments to Multiscale Simulations and Theoretical Predictions

Sorption thermal energy storage has become a key pathway for integrating renewable energy due to its reversible thermochemical storage properties. The activated carbon (AC)-water vapor system faces a core bottleneck of insufficient thermal energy storage density under low relative humidity. Current approaches often rely on trial-and-error methods to blindly enhance performance, resulting in substantial resource wastage. To address this issue, this study proposes an innovative “light experiment-multiscale simulation-thermodynamic model” strategy. This approach aims to quantify the adsorption structure–function relationship, enabling the targeted design of physicochemical properties based on desired material performance objectives. The experiment first established that 10 wt % H2O2 modification represents the optimal threshold concentration, enhancing the heat storage density of ACF by 78.80% under 25 °C & 30–40% RH. The 17 Å slit pore model qualitatively captures the adsorption trends of water vapor. Building upon this, multiscale simulations reveal that carboxyl (possessing the strongest water adsorption energy of −58.21 kJ/mol) and hydroxyl (increasing adsorption site density and stabilizing the adsorption network) are the key functional groups enhancing adsorption. More importantly, by leveraging the Do–Do finite simplified model and Dubinin-Polanyi adsorption thermodynamics theory, this study achieved continuous prediction of heat storage density across the entire humidity range. This provides both the theoretical basis and implementation pathway for top-down design of materials. The resource-efficient material design framework developed in this study holds promise for extension to fields such as refrigeration, dehumidification, and atmospheric water harvesting involving AC-water vapor adsorption system.