A novel shape stabilized phase change material based on Co/Zn co-modified porous carbon for thermal storage and photothermal conversion

Thermal storage technology is an efficient way to elevate the utilization efficiency of renewable energy and promote building decarbonization. Organic phase change material (PCM) is a typical medium in thermal storage system with the advantages of low supercooling degree, non-toxicity and ideal chemical stability. However, the practical application of organic PCM is limited by the melting leakage and low thermal conductivity. To this end, in situ N-doped carbon (ACN2) derived from chitin is prepared by CoCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/ZnCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> co-modification. Subsequently, stearic acid (SA) is encapsulated into ACN2 via the method of vacuum-assisted impregnation to synthesize SSPCM (ACN2/SA). Prepared ACN2/SA possesses superior shape stability with a phase change enthalpy of 117.49 J/g, supercooling degree of 0.35 °C and thermal conductivity of 0.41 W/(m•K). Results of characterizations indicate that ZnCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/CoCl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> co-modification can construct mesopore structure in ACN2, which provides capillary force and storage space to prevent SA leakage. Moreover, ACN2 shows an improved graphitization degree owing to the catalysis of cobalt during carbonization, which is the reason for the enhancement of thermal conductivity. ACN2/SA also demonstrates excellent photothermal conversion efficiency of 71.2 %, and its thermal properties remain stable after 200 heating/cooling cycles. Therefore, a novel strategy for preparing shape stabilized PCM with ideal thermal storage performance and photothermal conversion is put forward in this work, and the mechanism of interaction between support and PCM is revealed. ACN2/SA is potential using in the field of renewable energy and building decarbonization.