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The application of erythritol to medium-temperature latent heat energy storage systems is limited by its low thermal conductivity and large supercooling. Three types of graphite foams (GFs) with different thermal conductivities were used as the porous skeleton for encapsulating erythritol via vacuum impregnation, and the erythritol/GF composites were investigated using different methods to solve the aforementioned problems. The GF pores were effectively filled with erythritol via vacuum impregnation, and the filling rate of erythritol reached more than 90%. The thermal conductivity of the erythritol/GF composites was 73.80, 35.05, and 13.30 W/m·K. The thermal conductivity of the erythritol/GFs was improved by 26–158 times over that of pure erythritol. The subcooling degree of the erythritol/GF composites was reduced from 64.1 °C to 59.4 °C, facilitating the release of latent heat. The erythritol/GF composites had remarkably boosted thermal stability compared with that of pure erythritol. The developed erythritol/GF phase-change composite material exhibits excellent heat transfer and storage properties, and it has broad prospects in the field of phase-change heat storage at intermediate temperatures. • Ery/GF with high filling rate of erythritol was prepared by vacuum impregnation. • Thermal conductivity of Ery/GF composites were enhanced by 26–158 times. • Subcooling degree of Ery/GF composites were reduced from 64.1 °C to 59.4 °C. [ABSTRACT FROM AUTHOR]

In situ XRD, in situ Raman and TPSR were used to investigate the effect of Na promoter on the evolution of iron and carbon species and direct evidence for the Na promoter tuning the product distribution were obtained. The particle size of Fe 5 C 2 were decreased and the surface graphitic carbon species distribution were regulated, which favors the improvement of the stability of Fe 5 C 2 and inhibition of hydrogenation of carbon species to paraffins. • In situ XRD shows the addition of Na promoter inhibits the hydrogenation of Fe 5 C 2. • In situ Raman shows Na promoter inhibits the hydrogenation of surface carbon species. • TPSR indicates Na promoter increases the ratio of surface graphite carbon species. This study unravels the effect of Na promoter on the distribution of surface carbon species and the regulation of the chemical and structural evolution of Fe nanoparticles through in situ technologies, and illustrates the modification of carbon and iron species for olefins formation during CO 2 hydrogenation. With the contents of Na promoter increasing from 0 wt% to 0.5 wt%, the ratio of olefins to paraffins ranging from C 2 -C 7 rose greatly from 0.70 to 5.67. The increase in the density of Na on the Fe 5 C 2 surface improved the stability of Fe 5 C 2 by suppressing the further hydrogenation of Fe 5 C 2 , which could be directly confirmed by that the Fe 5 C 2 cannot be reduced by H 2 (450 °C, 0.1 MPa, 2 h) with the content of Na increasing of from 0% to 0.5%. In situ Raman spectra and temperature programed profiles have demonstrated that the presence of Na promoter has also proved to facilitate the carbon deposits by dissociation of CO and inhibit the reduction of surface carbon species by H 2 (350 °C, 0.1 MPa, 6 h). Consequently, the formation of olefins was enhanced by the inhibition hydrogenation of intermediate carbon species. [ABSTRACT FROM AUTHOR]