Optical Design and Preparation of WZr–SiZrO Nanocermet-Based Solar Selective Absorbing Coatings for High-Temperature Photothermal Conversion

The urgent need for next-generation concentrated solar power drives the pursuit of highly efficient, thermally stable, and scalable solar selective absorbing coatings (SSACs). So far, the commercially available nanocermet-based SSACs (such as Mo–SiO2, Mo–Al2O3, and W–Al2O3 coatings) suffer from optical performance degradation due to structural collapse under a high-temperature and weak oxidizing atmosphere. To address this challenge, the SiZrO dielectric and WZr–SiZrO nanocermet are developed and employed to construct SSACs. In order to obtain excellent optical performance [using the photothermal conversion efficiency (η) as the criterion], we first utilize theoretical simulations to determine the structural parameters of the target coatings. With this guidance, the WZr–SiZrO nanocermet-based SSACs are experimentally prepared, demonstrating high solar absorptance (96.8%), low emittance (14.0%@500 °C), and incident light angle insensitivity (0–56°). Benefiting from the improved thermal stability and oxidation resistance of the component materials, the prepared SSACs have enhanced high-temperature durability, maintaining η = 84.3% even after annealing at 650 °C in 0.2 Pa for 635 h. These results suggest that the well-designed WZr–SiZrO nanocermet-based SSAC is promising for use in high-temperature photothermal conversion.