Enhancing the thermoelectric characteristics of thermoelectric cement matrix composites by (Ca0.87Ag0.1La0.03)3Co4O9 binary metal oxide

In recent years, the expansion of urban buildings has caused buildings and road surfaces to absorb large amounts of heat energy during the summer, exacerbating the heat island effect. The application of thermoelectric cement matrix composites can convert the surface heat energy of roads and buildings into electrical energy. The performance enhancement for thermoelectric cementitious composites is shown by the addition of carbon materials and metal oxides, and great research progress has been made. The current research on metal oxides as functional fillers is mostly for monomeric metal oxides and less for binary metal oxides. In this study, (Ca0.87Ag0.1La0.03)3Co4O9 was produced by co-precipitation, and a strategy to enhance the thermoelectric characteristics of thermoelectric cement matrix composites was suggested. To reduce surface defects, this approach involved pretreating the (Ca0.87Ag0.1La0.03)3Co4O9 with hydrochloric acid. Using acid etching to transform the metal oxides' morphology from granular to layered, the interface was expanded, improving carrier scattering and, in turn, the Seebeck coefficient. The thermoelectric characteristics of cement substrates with low content, acid-treated (Ca0.87Ag0.1La0.03)3Co4O9, and a fixed mass fraction of expanded graphite were compared to a control group without acid treatment. The results showed that the method resulted in an increase of the Seebeck coefficient to −100.5 μV/°C and the introduction of nano-silver inclusions caused an increase of the conductivity to 13.5S/cm. The improvement of the Seebeck coefficient and electrical conductivity has increased the power factor to 13.8μWm−1K−2. This study proposes a method to improve the thermoelectric properties of cement matrix composites.