Efficient solar-driven interfacial steam-hydropower co-generation by high-quality carbon nanotube from discarded polyolefin separator

Abstract

Converting discarded polyolefin separators into valuable carbon nanotubes (CNTs) not only contributes to the high-value utilization of discarded separators, but also offers a green approach to construct advanced CNT-based generators. However, the controlled carbonization of discarded polyolefin separators into high-quality CNTs remains challenging, and the mechanism of electricity generation in CNTs remains obscure. Herein, we report the “all-in-one” catalytic strategy using multi-component Ni/Mo/Mg catalysts to realize the controllable carbonization of discarded polyolefin separators into high-quality CNTs. By adding Mo and Mg to Ni in a molar ratio of 5/0.1/0.5 (Ni/Mo/Mg), the catalyst displays high catalytic activity, dispersion, and stability, and achieves a CNT yield of 57.4 wt%. Thanks to the good photothermal conversion capability and excellent wettability, the CNT evaporator achieves an evaporation rate of 2.73 kg m^-2 h^-1, a photo-to-thermal efficiency of 95.4%, and an open-circuit voltage of 0.221 V under laboratory conditions, which ranks as one of the most efficient evaporators/generators. In practical experiments, the total water production and voltage output are 2.51 kg m^-2 over 5 h and 0.215-0.265 V, respectively. Molecular dynamics simulation results show that the surface functional groups interact more strongly with H⁺ than with OH^-. With the continuous evaporation of bulk water, H⁺ moves faster upward along the nanochannel than OH^-, thus forming a potential difference. This study provides an eco-friendly route for synthesizing advanced carbon nanomaterials and co-generating freshwater and electricity.

Keywords

Interfacial solar steam generation / freshwater-electricity co-generation / carbon nanotube / solar-to-thermal conversion / discarded polyolefin separators

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