Efficient Photo-Thermo-Electric Conversion Using Polyoxovanadate in Ionic Liquid for Low-Grade Heat Utilization.

A large fraction of energy, including solar energy, is dissipated into ambient atmosphere as low-grade waste heat. Efficient utilization of such energy is critical to address the current energy crisis and global warming issue. Herein, the efficient near-IR (NIR)-photothermal, thermoelectric, and thus photo-thermo-electric conversion of polyoxovanadate compound {[Ni(1,10-phenanthroline)3 ][V14 O34 Cl]Cl, NiV14 } in ionic liquid was achieved. The solution displayed a NIR-photothermal efficiency of 16.04 and 23.43 % at 808 and 1064 nm, respectively. Taking advantage of the synergetic thermodiffusive and thermogalvanic effects of various ion species in NiV14 solution, an open circuit voltage of approximately 0.45 V was obtained at ΔT=70 K generated by physical heating or NIR irradiation, indicating a large Seebeck coefficient of 6.38 mV K-1 and an optimized thermal power at 1.2 W m-2 . The polyoxovanadate-ionic liquid system offers a new platform for efficiently utilizing not only low-grade thermal energy but also solar energy for electricity generation.