Bimetallic cobalt-nickel oxide textured coatings for high-temperature concentrated solar power

This study reports a novel coating with enhanced solar absorptance and reduced thermal emittance with high efficiency at elevated temperature for next-generation concentrated solar power (CSP) plants, with targeted operating temperatures around 750 °C. Highly textured cobalt-nickel oxide (CNO) coatings were electrodeposited onto Inconel substrate by systematically varying the molarity of cobalt and nickel nitrate aqueous electrolytes and the relative percentage of the two metals. The optimized CNO coating exhibited micro-to-nano structures designed to match the wavelengths in the visible region of the solar spectrum. These structures facilitate resonant absorption of solar radiation, significantly boosting solar absorption and accommodating thermal stress during high temperature exposure. A high solar absorptance of about 0.97 and a low thermal emittance of 0.66 were achieved for the optimized coatings, which remained robust (absorptance of 0.95 and emittance of 0.43) after 100 h of isothermal exposure to 750 °C in air. The innovative approach presented in this study demonstrates the potential for tailoring air-stable solar absorber coatings to achieve high absorption, low emittance, and excellent high-temperature endurance, meeting the rigorous demands of next-generation CSP systems. •Presents novel fractal-textured solar absorber coatings of cobalt nickel oxide.•Coatings are fabricated by low-cost electrodeposition.•Coatings feature a high solar absorptance of 0.97 and low emittance.•Coatings do not require an anti-reflective layer.•Optical properties are durable under prolonged exposure at 750 °C in air for 100 h.