Expanded Graphite/Cement Composites for Large-Scale Energy Harvesting: Structural Control and Thermoelectric...

Area of Science:

• Materials Science
• Energy Harvesting
• Thermoelectric Materials

Background:

• Building structures accumulate significant low-grade thermal energy from prolonged sun exposure.
• Cement-based composites with expanded graphite (EG) offer thermoelectric potential for heat harvesting.
• The impact of EG particle size and cement mineral composition on thermoelectric properties remains unclear.

Purpose of the Study:

• To investigate the effect of multi-particle size expanded graphite (EG) on the thermoelectric properties of EG/cement-based composites.
• To explore the synergistic influence of C2S and C4A3S̅ cement clinker minerals on thermoelectric performance.
• To optimize EG/cement-based composites for efficient large-scale heat harvesting and energy supply.

Main Methods:

• Preparation of EG/cement-based composites using acid-etched EG of varying particle sizes.
• Incorporation of high-purity C2S and C4A3S̅ cement clinker monominerals.
• Characterization of thermoelectric properties, including electrical conductivity and Seebeck coefficient.

Main Results:

• Synergistic effect of multi-particle size EG significantly improved the connectivity of the EG conductive network.
• The combination of C2S and C4A3S̅ enhanced carrier mobility in the EG/cement-based composites.
• Achieved peak thermoelectric properties: 7.43 S/cm electrical conductivity, -65.69 μV/K Seebeck coefficient, and 3.23 μW m⁻² K⁻² power factor.

Conclusions:

• Multi-particle size EG and synergistic cement mineral composition are key to enhancing thermoelectric properties.
• EG/C2S-C4A3S̅ composites demonstrated significantly improved power factors compared to composites with single minerals.
• This research highlights a promising pathway for developing efficient thermoelectric materials for building-integrated energy harvesting.