Waste to Wealth:\nDiscarded Cigarette Butt-Derived\nMetal-Free N‑Rich Carbon Catalysts for the Selective Catalytic\nOxidation of Hydrogen Sulfide to Sulfur

The selective catalytic oxidation of toxic gas H<sub>2</sub>S to\nelemental sulfur (H<sub>2</sub>S-SCO) is a promising desulfurization\nprocess known for its dual benefits of recovering valuable sulfur\nresources and mitigating environmental pollution. Nevertheless, developing\ncost-effective and efficient catalysts for H<sub>2</sub>S-SCO remains\na significant challenge. In this study, we synthesized a low-cost\nand metal-free nitrogen-rich carbon catalyst (NrCC) by copyrolyzing\ndiscarded cigarette butts (organic solid wastes that are difficult\nto degrade naturally) with urea for the continuous H<sub>2</sub>S-SCO\nprocess at a relatively low temperature. The NrCC exhibited exceptional\ncatalytic performance, achieving complete H<sub>2</sub>S conversion\nto sulfur at 180 °C, and demonstrated excellent stability in\nhumid (RH = 80%) and high CO<sub>2</sub> concentration environments.\nThe catalyst succeeded due to its developed pore structure (specific\nsurface area as high as 2267.77 m<sup>2</sup>·g<sup>–1</sup>) and abundant pyridine-N sites. DFT calculations showed that the\npyridine-N neighbor carbon sites were the active sites promoting H<sub>2</sub>S adsorption and dissociation. This study presents a novel\n“waste control by waste” strategy that integrates the\nutilization of organic solid waste resources with air pollution control\nmeasures, showcasing the potential for sustainable environmental solutions.