Sprayable superblack photothermal coating on flexible cellulose paper for high-efficiency anti-icing applications

Flexible superblack materials are essential for stray light management in optical systems and hold great promise for solar-energy harvesting. However, their development is often limited by complex fabrication processes, high costs, and poor compatibility with flexible non-planar surfaces. Here, we demonstrated a novel sprayable strategy to create a high-performance, flexible superblack photothermal coating by directly engineering the inherent spongy fibrous network microporous structure of cellulose DF (dust-free) paper, which acts as an efficient light-trapping geometry. This unique structure is functionalized by uniformly integrating carbon black (CB) nanoparticles within the cellulose matrix, forming a continuous, three-dimensional photon-absorbing spongy network that minimizes reflection through multiple internal scattering within the sp² hybrid orbital and interlayer of CB as well as particle/particle and particle/fiber interface gaps on the molecular level and nanoscale level, respectively. Further, this modification confers excellent superhydrophobicity (water contact angle > 157°) to the paper due to the synergistic effects of the hydrophobic agents and micro-nano structures on the surface of the paper. The resulting paper-based composite exhibits an outstanding solar-weighted absorptance of 98.2% across the 200–2500 nm spectrum and presents efficient photothermal conversion behavior, rapidly reaching 119 °C from ambient temperature under 1 sun irradiation within 60 s. The synergistic combination of broadband light absorption, efficient heat generation, and water-repellent properties enables effective photothermal anti-icing functionality (a freezing delay of 420 s, −20 °C, and 1 sun). This work provides a simple and scalable approach to fabricate mechanically flexible, multifunctional superblack materials by leveraging the natural structure of cellulose paper, opening new avenues for their applications in flexible solar thermal management.