Engineering and Optimization of Stable 2-Dimensional MXene-Based Nanofluid for Direct Absorption Photothermal Energy Conversion

The world is striving to design renewable energy systems to reduce reliance on finite fossil fuels and minimize environmental impacts. Photothermal nanofluids (NFs) in solar energy harvesting center on achieving a delicate balance between effective solar absorption, light-to-heat thermal conversion, dispersion stability, and viscosity. This study focuses on the formulation of high-performance stable NFs by incorporating different mass fractions of sodium ascorbate-treated ultrathin 2-dimensional (2D) Ti₃C₂T_x MXene nanosheets (SA-TMS) in ethylene glycol (EG) base fluid. Optical and photothermal characterization of the NF, including dispersion, suspension stability, viscosity, and photothermal conversion, were thoroughly examined for the prepared series. Interestingly, compared to pure EG, adding 0.0018 wt % of SA-TMS improved the photothermal performance of EG by 68.73%, credited to the large extinction coefficient of 64.4 l/(g·cm) and localized surface plasmon resonance effect of high conductive ultrathin SA-TMS nanosheets. Furthermore, the optimized SA-TMS/EG^o NF was semitransparent with a minimum effective viscosity of 18.88 mPa·s because of its exceptional self-lubricating properties. In addition to having a good cycling life, the recruited SA-TMS/EG NFs showed no signs of sedimentation after 90 d and showed promising shelf stability. Furthermore, the photothermal conversion performance study proved that large-size 2D sheets are more efficient than smaller-size sheets. This comprehensive study opens an exciting regime to design stable and efficient 2D material-based NFs for direct solar energy harvesting, leveraging their enhanced thermal conductivity and optically semitransparent nature.