Cu2+-polydopamine coordination enabled superior solar-thermal-electric conversion of boron nitride-based phase change composites

The application of phase change materials (PCMs) in solar energy harvesting and storage is restricted by low thermal conductivity, liquid leakage, and insufficient solar-thermal conversion efficiency. Previous enhancement strategies often suffered from nanoparticle aggregation and limited control over nanoparticle growth. Herein, we utilized Cu2+-polydopamine (PDA) coordination to enable efficient in-situ growth of copper nanoparticles (CuNPs) on boron nitride (BN). The resulting BN/PDA/Cu carrier exhibited a robust surface, with CuNPs forming a dense, coral-like multilayered nanocoating that significantly reduced interfacial thermal resistance. By adsorbing polyethylene glycol (PEG) with the carrier, the prepared PEG/BN/PDA/Cu composite exhibited a remarkable thermal conductivity of 5.741 W/(m∙K), 17.9 times higher than that of pure PEG. In addition, the composite exhibited a melting enthalpy of 170.8 J/g, excellent thermal reliability over 500 cycles, and maintained shape stability without leakage at 70°C. Furthermore, the synergy of PDA and CuNPs substantially enhanced the solar-thermal-electric conversion performance of the composite. Under 100 mW/cm2 sunlight, the composite achieved an outstanding solar-thermal conversion efficiency of 95.1% and a stable current output of 62 mA. Compared to the conventional solution deposition method, the PDA-enabled in-situ growth method significantly improved both the quality and quantity of CuNPs anchored on the carrier surface, thereby further enhancing the thermal conductivity and solar-thermal conversion efficiency of the composite. Moreover, our method used CuNPs as a cost-effective enhancer and prevented their aggregation and settling during long-term thermal cycles. The developed phase change composites showcased great potential for advanced solar energy harvesting and thermal management.