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·m⁻²·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.