Effect of in-situ synthesized nano hexagonal boron nitride on thermal properties of chloride salts for thermal energy storage

Chloride salts are regarded as promising candidates for thermal energy storage in concentrated solar power systems, but their low thermal conductivity and specific heat capacity limit their further development and application. Herein, utilizing sodium tetraborate decahydrate and melamine as precursors, nano hexagonal boron nitride (h-BN) was synthesized in situ within NaCl-KCl through spray drying to obtain modified salts. The results indicated that in-situ synthesized h-BN nanosheets (∼50 nm) were uniformly dispersed without obvious agglomeration and exhibited excellent chemical compatibility. Remarkably, modified salts showed a non-linear specific heat capacity increase, reaching a maximum 40.5% enhancement at 1.5 wt.%. Molecular dynamics simulations attribute this to the formation of cation-enriched interfacial layers surrounding h-BN. Simultaneously, the thermal conductivity of modified salts was enhanced from 0.78 to 1.41 W/(m·K) at the optimal loading. Modified salts maintained good thermal properties after 50 thermal cycles, indicating their promising applications in solar thermal energy storage.