Photocatalytic Solar\nHydrogen Generation by SWCNT-Supported\nNickel Oxide Nanoparticles Wrapped by Polypyrrole

High-performance and noble metal-free green hydrogen\ngeneration\nfrom water by photocatalysis is a reliable and sustainable approach\nto solving energy and environmental problems. We report a study on\na hybrid nanocomposite photocatalyst of polypyrrole (PPy), nickel\n[nickel oxide (NiO)], and single-walled carbon nanotubes (SWCNTs)\nthat was produced cost-effectively. The optimal design of the catalyst\nwith the incorporation of 4 wt % of SWCNTs is sensitive to the crystallite\nsize and lattice strain, which tune the optical energy gap for solar\nirradiation activity. Also, NiO acts as a conducting channel between\nthe PPy-coated SWCNTs, facilitating high charge transportability.\nThe photoexcited charge separation efficiency is accelerated in the\npresence of SWCNTs. Finally, cooperative agreement on the energy levels\nof the individual component promotes remarkable hydrogen (H<sub>2</sub>) generation, harnessing the full band spectrum of simulated sunlight\nin the presence of only 1 vol % methanol as a photosensitizer. The\nsolar H<sub>2</sub> evolution rate is improved by factors of 22.4\nand 5.6 compared to that of the pristine PPy and PPy-NiO (PNC0) hybrid.\nThis work delivers a facile and simple approach to developing a highly\nefficient noble metal-free carbon-based organic–inorganic composite\nsystem for solar photocatalytic H<sub>2</sub> generation.