Bio-inspired thermoelectric cement with interfacial selective immobilization towards self-powered buildings

Buildings and infrastructure significantly contribute to global energy consumption and CO₂ emissions. Transforming cement, the most widely used construction material, into a functional medium for heat harvesting presents a promising avenue to offset the energy demands of buildings. The disparity in diffusion rate between cations and anions within cement pore solution due to variations in interactions with pore walls, endows cement with inherent ionic thermoelectric properties. However, the isolation of pores by the dense cement matrix hinders the rapid transportation of ions with superior diffusion rates, impeding the enhancement of mobility difference between ions and limiting the enhancement of Seebeck coefficient. Inspired by the stem structure of plants, we present a cement-polyvinyl alcohol (PVA) composite (CPC) featuring aligned cement and PVA hydrogel layers. While PVA hydrogel layers provide ion diffusion highways for OH^- ions, cement-PVA interfaces establish strong coordination bonds with Ca²⁺ ions and weaker interactions with OH^- ions, enabling selective immobilization, which amplifies the diffusion rate disparity between Ca²⁺ and OH^-. The CPC's multilayer structure yields abundant interfaces, providing ample interaction sites that maximize the contribution of cement ions to thermoelectric performance. The as-prepared composite achieves an impressive Seebeck coefficient of -40.5 mV/K and a figure of merit (ZT) of 6.6 × 10^-2. Due to the engineered multilayer structure, the CPC also demonstrates superior mechanical strength and intrinsic energy storage potential, which has been assembled into a self-powered architecture. The biomimetic structure and interfacial selective immobilization mechanism may pave the way for the design and fabrication of high-performance ionic thermoelectric materials.