Self-enhancing photothermal conversion of 2D Weyl semimetal WTe2 with topological surface states for efficient solar vapor generation

To improve the performance of solar energy-driven water generation, two-dimensional (2D) photothermal materials requisite to be optimized by some strategies such as alloying, combination of plasmonic and defect modulation. However, the challenges faced in practical utilization are the complex preparation process and insufficient solar spectrum absorption. Herein, we propose a strategy of self-enhancing photothermal performance induced by topological surface states (TSSs). 2D WTe2 is fabricated on the mixed cellulose ester (MCE) for photothermal device. Compared to the MCE and pure water, WTe2 @MCE has an excellent photothermal evaporation rate of 1.09 kg center dot m(-2)center dot h(-1) upon 1 sun irradiation, promoting 6.1 and 3.1 times, respectively. It can be attributed to the characteristics of 2D Weyl semimetal WTe2 with TSSs bringing about high optical absorption capacity, low thermal diffusivity, specific heat capacity, and high carrier density, which are strongly proved by experiments and calculation. More importantly, the contribution of TSSs to the enhancement of optical absorption for efficient solar water generation is revealed by the comparative experiment between 2D WTe2 with TSSs and that without TSSs. Furthermore, photothermal conversion mechanism is explored in-depth understanding that the photoexcited electrons recombinate with the holes through nonradiative mode for releasing thermal energy by phonons emission via multiple pathway. This work promotes the application of Weyl semimetal material with TSSs in solar water evaporation.

Automated summary

In order to improve the performance of solar energy-driven water generation, optimization strategies such as alloying and combination of plasmonic and defect modulation are required for two-dimensional (2D) photothermal materials. However, the complex preparation process and insufficient solar spectrum absorption pose challenges in practical utilization. This study proposes a self-enhancing photothermal performance strategy induced by topological surface states (TSSs). By fabricating 2D WTe2 on mixed cellulose ester (MCE), a photothermal device with WTe2 @MCE exhibits an excellent photothermal evaporation rate, 1.09 kg·m(-2)·h(-1), which is 6.1 and 3.1 times higher than MCE and pure water, respectively. This improvement can be attributed to the characteristics of 2D Weyl semimetal WTe2 with TSSs, including high optical absorption capacity, low thermal diffusivity, specific heat capacity, and high carrier density, which are supported by experiments and calculations. The contribution of TSSs to the enhancement of optical absorption for efficient solar water generation is revealed through comparative experiments. Furthermore, the photothermal conversion mechanism is explored, revealing that the photoexcited electrons recombine with the holes through nonradiative mode, releasing thermal energy through phonon emission via multiple pathways. This work promotes the application of Weyl semimetal material with TSSs in solar water evaporation.