Systematic investigating on the broadband solar absorption and photo-thermal conversion performance of TiN@rGO plasmonic nanofluids

Strong solar capture and high heat transfer are extremely vital for designing solar-to-heat absorber to improve photo-thermal conversion efficiency in direct absorption solar collectors (DASCs). In this paper, the plasmonic nanofluids containing reduced graphene oxides (rGO) decorated with titanium nitride (TiN) nanoparticles were prepared. Their superior solar-thermal conversion efficiency and heat transfer property was based on the synergy between the Localized Surface Plasmon Resonances (LSPR) effect of TiN and the high thermal conductivity of rGO. The optical properties of plasmonic nanofluids were investigated with the concentration and penetration depth, which indicated that the existence of TiN on graphene could improve the light-capture ability. The results indicated that the TiN@rGO plasmonic nanofluids could be used for DASCs applications, even under the low mass concentrations. Specifically, the maximum photo-thermal conversion efficiency of the plasmonic nanofluids was 66.74% at 40 ppm concentration, which was about 23% higher than that of pure water. And, the experimental results show that the photothermal conversion efficiency will be reduced if the nanofluid concentration is higher than the optimal concentration. This work exhibited the potential application of plasmonic-graphene nanofluids in DASCs.