High-performance solar vapor generation of Ni/carbon nanomaterials by controlled carbonization of waste polypropylene

Solar vapor generation is emerging as a promising technology using solar energy for various applications including desalination and freshwater production. However, from the viewpoints of industrial and academic research, it remains challenging to prepare low-cost and high-efficiency photothermal materials. In this work, we report the controlled carbonization of polypropylene (PP) using NiO and poly(ionic liquid) (PIL) as combined catalysts to prepare a Ni/carbon nanomaterial (Ni/CNM). The morphology and textural property of Ni/CNM are modulated by adding a trace amount of PIL. Ni/CNM consists of cup-stacked carbon nanotubes (CS-CNTs) and pear-shaped metallic Ni nanoparticles. Due to the synergistic effect of Ni and CS-CNTs in solar absorption, Ni/CNM possesses an excellent property of photothermal conversion. Meanwhile, Ni/CNM with a high specific surface area and rich micro-/meso-/macropores constructs a three-dimensional (3D) porous network for efficient water supply and vapor channels. Thanks to high solar absorption, fast water transport, and low thermal conductivity, Ni/CNM exhibits a high water evaporation rate of 1.67 kg m-2 h-1, a solar-to-vapor conversion efficiency of 94.9%, and an excellent stability for 10 cycles. It also works well when converting dye-containing water, seawater, and oil/water emulsion into healthy drinkable water. The metallic ion removal efficiency of seawater is 99.99%, and the dye removal efficiency is >99.9%. More importantly, it prevails over the-state-of-art carbon-based photothermal materials in solar energy-driven vapor generation. This work not only proposes a new sustainable approach to convert waste polymers into advanced metal/ carbon hybrids, but also contributes to the fields of solar energy utilization and seawater desalination.