Photothermal-healing, and record thermal stability and fire safety black phosphorus–boron hybrid nanocomposites: mechanism of phosphorus fixation effects and charring inspired by cell walls

Abstract

Inspired by the structure and good thermal resistance of cell walls in plants, we herein develop a life-cycle safe multifunctional nanocomposite of a polycarbonate/black phosphorus–boron nanohybrid (PC/BP–B) with properties of photothermal-healing, thermal stability and fire safety. In the first place, the photothermal conversion capability of PC/BP–B_1.0, evidently increases with the irradiation power (r² > 0.994), which indicates a 99.28% recovery of tensile strength. Secondly, by studying the chemical responses of BP to heat, we find that PC/BP–B exhibits self-assembly behavior driven by fire where BPO₄ serves as a node inspired by the cell wall. This unique structure can not only bridge carbonate groups and fix phosphorus compounds, but also capture pyrolysis products and catalyze charring. It helps PC/BP–B_1.0 achieve better thermal stability and fire safety with a 57.16 °C increase in T_−1% and a 70.50% decrease in the heat release rate. Furthermore, the pyrolysis products of polycarbonate-based polymers and black phosphorus-based hybrids (CO₂ and P₄, P₃, and P₂) in the gas phase are also analyzed in this research. Finally, PC/BP–B_1.0 can fully keep phosphorus in the condensed phase, which provides a nature-inspired strategy for reducing the release of phosphorus compounds during pyrolysis that may be detrimental to human health and the ecological environment. This work paves a general path for the design and application of nanocomposites with superior properties of crack healing, thermal stability and fire safety.