Investigation of optical absorption and photothermal conversion characteristics of binary CuO/ZnO nanofluids

This work aimed at studying the optical absorption and photothermal conversion of binary CuO/ZnO nanofluids that can be used as catalysts in methanol reforming hydrogen production. A series of different component CuO/ZnO composite nanoparticles were prepared via a co-precipitation method, and showed the features of uniform diameter distribution, high crystallinity and single crystal structure. The optical absorption, thermal conductivity and photothermal conversion of the composite oxide nanofluids based on water were investigated. The transmission spectrum tests show that the optical absorption properties of the composite oxide nanofluids are effectively enhanced with the introduction of ZnO in visible light band. And the thermal conductivity tests indicate that the thermal conductivity of the binary CuO/ZnO composite nanofluids is higher than that of the pure CuO. The photothermal conversion results show that, due to the addition of ZnO, the photothermal conversion performance of the CuO/ZnO composite nanofluids has been enhanced, and the maximum temperature of the nanofluid reaches about 72.649 degrees C with the volume fraction of 0.01%, which possesses the highest photothermal efficiency of 97.35% at 30 degrees C and 34.70% at 70 degrees C. This implies a simple approach to enhance photothermal conversion for efficient solar energy utilization.