Synergistic pyridinic N and Fe sites in electrospun carbon nanofibers for economical catalytic synthesis of high-value COS from low-concentration H₂S

Abstract

The efficient upgrading of low-concentration H₂S into valuable chemicals remains an unresolved economic challenge, as conventional catalytic processes have difficulty handling low-concentration H₂S. Herein, we develop a new decoupled sulfidation-reduction catalytic cycle strategy that transforms low-concentration H₂S in blast furnace gas into high-value carbonyl sulfide (COS). To implement this strategy, we designed a novel Fe-modified carbon nanofiber catalyst (Fe-CNF-15) for efficient H₂S enrichment, followed by a reduction step utilizing the CO present in blast furnace gas to produce COS. Fe-CNF-15 delivers a sulfur capacity of 0.926 mmol∙g_cat.^–1 and achieves a high COS yield of up to 96.13% over three consecutive cycles, demonstrating significant potential for high-value COS synthesis. The high performance of Fe-CNF-15 is attributed to the synergistic interplay between pyridinic nitrogen species and dispersed Fe sites, which creates favorable coordination environments for sulfur conversion. Density functional theory calculations reveal that the Fe₃NC motif enables strong Fe-S interaction through Fe-d and S-p orbital coupling, regulates the adsorption of sulfur-containing intermediates, and promotes the overall H₂S-to-COS conversion pathway. This work provides a feasible strategy for the conversion of low-concentration H₂S and offers valuable insights for the design of efficient catalysts.

Graphical abstract

Keywords

low-concentration H₂S conversion / carbonyl sulfide synthesis / Fe-modified carbon nanofibers / pyridinic nitrogen active sites / sulfidation-reduction cycling

References

[1] Huang R , Yan H P , Shen L J , Lei G C , Zheng X H , Wang S P , Zhan Y Y , Liang S J , Jiang L L . Highly selective and stable hydrogenation of CO₂/H₂S to methyl mercaptan over a synergistic Cu-Mo catalyst. ACS Catalysis, 2026, 16(12): 11135–11146

[2] Zheng X H , Cai J M , Zhao W T , Liang S J , Zheng Y , Cao Y N , Shen L J , Xiao Y H , Jiang L L . Porous α-Fe₂O₃/SnO₂ nanoflower with enhanced sulfur selectivity and stability for H₂S selective oxidation. Chinese Chemical Letters, 2021, 32(7): 2143–2150

[3] Sun L X , Li Q X , Li K Y , Chu J C , Li Y S , Wang M T , Chen Z , Ma X H , Yi S L . State-of-the-art polymeric membranes and polymer derived membranes for simultaneous CO₂ and H₂S removal from sour natural gas. Frontiers of Chemical Science and Engineering, 2025, 19(5): 40

[4] Aminuddin M S , Bustam M A , Johari K . Latest technological advances and insights into capture and removal of hydrogen sulfide: a critical review. RSC Sustainability, 2024, 2(4): 757–803

[5] Chan Y H , Loy A C M , Cheah K W , Chai S Y W , Ngu L H , How B S . Hydrogen sulfide (H₂S) conversion to hydrogen (H₂) and value-added chemicals: progress, challenges and outlook. Chemical Engineering Journal, 2023, 458: 141398

[6] Li X , Wang X Q , Yuan L , Wang L L , Ma Y X , Wu Y , Xie Y B , Cao R , Xiong Y R , Ning P . COS and H₂S simultaneous removal from blast furnace gas over a tailored Cu/Zr Co-doped K@TiO₂ bifunctional catalyst under low temperature. Chemical Engineering Journal, 2023, 471: 144573

[7] Yu M , Chang M W , Kosinov N , Hensen E J M . Alkali catalyzes methanethiol synthesis from CO and H₂S. Journal of Catalysis, 2022, 405: 116–128

[8] Ren X X , Filot I A W , Hensen E J M . A density functional theory study of the formation of COS from CO and H₂S on cesium sulfide. Journal of Catalysis, 2024, 438: 115731

[9] Batool S R , Fabbiani M , Novikov A , Ghassemi R , Zareghorbaei S , Lauwaert J , Pinard L , Retot H , Thybaut J W , Valtchev V . Acid gas valorization through a carbonyl sulfide (COS) intermediate over Na-containing FAU and LTA zeolites. Catalysis Today, 2026, 466: 115660

[10] Zhao C Q , Huang K Y , Xu Z X , Zhao Q , Xu H Q , Wu Y T , Shi M Z , Zhang X M . Carbonyl-functionalized hydrophobic ionic liquids for the efficient capture and conversion of H₂S. AIChE Journal, 2026, 72(7): e70385

[11] Cao R , Wang X Q , Wang L L , Cao F X , Li X , Wang L , Xiang J H , Ning P . Construction of La/Al₂O₃ nanorod-like catalyst with rich basic sites: enabling efficient conversion of COS-superior selectivity and theoretical insights. Chemical Engineering Journal, 2024, 499: 155752

[12] Georgiadis A G , Charisiou N D , Goula M A . Removal of hydrogen sulfide from various industrial gases: a review of the most promising adsorbing materials. Catalysts, 2020, 10(5): 521

[13] Pu H Y , Liu Y R , Xu Z Z , Fang J , Song T P , Qin C Y , Lu J C , Luo Y M . Synergistic control and resource utilization of carbonyl sulfur (COS) and hydrogen sulfide (H₂S) over oxidized K-Mo materials. Environmental Science & Technology, 2026, 60(23): 17037–17050

[14] Yu T , Zheng J Y , Su S K , Wang Y D , Xu J H , Liu Z D . Zinc oxide nanoclusters encapsulated in MFI zeolite as a highly stable adsorbent for the ultradeep removal of hydrogen sulfide. JACS Au, 2024, 4(3): 985–991

[15] Yin M X , Pillai S C , Wang H L , Fan F Y , Hou H . Enhanced H₂S removal efficiency using CuO/Al₂O₃ catalyst impregnated with Ca(NO₃)₂: influence of calcination temperature and mechanistic insights. Process Safety and Environmental Protection, 2024, 192: 1543–1553

[16] Guo M M , Wang R Y , Gu J N , Feng Y , Guo F R , Zhan G M , Wang L J , Li K , Li H , Jia J P . et al. Oxygen-deficient Fe₂O₃ bearing pyridine n moieties for spatially decoupled selective H₂S oxidation into sulfur at intermediate temperatures. Journal of Hazardous Materials, 2026, 502: 140982

[17] Hong G R , Kim K J , Shin B G , Roh H S . Revealing sulfur-resistant Pt-CeO₂ interfacial sites for water-gas shift catalysts toward waste-to-hydrogen. Green Chemistry, 2026, 28(18): 8004–8016

[18] Wang X Z , Boukhvalov D W , Ahmadi Y , Younis S A , Szulejko J E , Ali Maitlo H , Kim K H . Reactive adsorption and catalytic oxidation of gaseous hydrogen sulfide using a prototype air purifier built with bismuth-doped titanium dioxide. Journal of Hazardous Materials, 2024, 478: 135412

[19] Chen L Y , Ma J , Peng J , Song T , Liu K L . Effect of CuO addition on the performance of V₂O₅-based oxygen carriers for chemical-looping oxidation of H₂S for efficient sulfur recovery from natural gas. Fuel, 2023, 337: 126898

[20] Altalhi A A , Mohamed E A , Negm N A . Recent advances in layered double hydroxide (LDH)-based materials: fabrication, modification strategies, characterization, promising environmental catalytic applications, and prospective aspects. Energy Advances, 2024, 3(9): 2136–2151

[21] Yang J T , Cui S , Zhao F , Wang F , Feng J Y , Ning P , Jia L J . Waste to wealth: discarded cigarette butt-derived metal-free N-rich carbon catalysts for the selective catalytic oxidation of hydrogen sulfide to sulfur. Environmental Science & Technology, 2024, 58(45): 20267–20276

[22] Dong Q , Chen S W , Lv C M , Wang J T , Ma C , Qiao W M , Ling L C . Hierarchical porous nitrogen-doped carbon nanosheets modified with sodium hydroxide for efficient removal of hydrogen sulfide at room temperature. Industrial & Engineering Chemistry Research, 2025, 64(20): 9960–9973

[23] Feng J Y , Zhao F , Xiang H , Wang F , Cui S , Pan Z B , Cao R , Ning P , Jia L J . Nitrogen sites induce homogeneous dispersion of iron species on biochar for enhanced hydrogen sulfide removal in a low-temperature anaerobic environment. Bioresource Technology, 2026, 440: 133496

[24] Liu X , Fu H Q , Xu C , Xu B , Liu Z Q , Giambastiani G , Pham-Huu C , Liu Y F . Stable and active axial N-coordinated Ni single-atom catalyst for catalytic desulfurization. ACS Catalysis, 2026, 16(5): 4690–4700

[25] Malik W , Victoria Tafoya J P , Doszczeczko S , Jorge Sobrido A B , Skoulou V K , Boa A N , Zhang Q , Ramirez Reina T , Volpe R . Synthesis of a graphene-encapsulated Fe₃C/Fe catalyst supported on sporopollenin exine capsules and its use for the reverse water-gas shift reaction. ACS Sustainable Chemistry & Engineering, 2023, 11(44): 15795–15807

[26] Krishnan S G , Bose B A , Kalarikkal N , Thomas S , Nzihou A . Effect of structural defects on electrical conductivity of graphitic biocarbon. ACS Omega, 2025, 10(39): 45323–45333

[27] Gao W Q , Meng Y , Zhang X R , Liu L Q , Zhang Y J , Zhou J , Sun Z F . Synthesis of Fe-CNFs and mechanistic insights into carbon-water reaction. Nanomaterials, 2026, 16(11): 700

[28] Mokhtari F , Groetsch T , Heidarian P , Maghe M , Varley R J . Functionalizing PAN carbon nanofibers using Ti₃C₂T_x MXene for improved thermal and electrochemical behavior. Macromolecular Rapid Communications, 2025, 46(21): e2500489

[29] Zhang Y S , Yang X M , Bao J P , Qian H , Sui D , Wang J S , Xu C C , Huang Y F . Electrospun porous carbon nanofibers derived from bio-based phenolic resins as free-standing electrodes for high-performance supercapacitors. Frontiers of Chemical Science and Engineering, 2023, 17(5): 504–515

[30] Li S X , Xing G Y , Zhao S , Peng J , Zhao L F , Hu F , Li L L , Wang J Z , Ramakrishna S , Peng S J . Fe-N Co-doped carbon nanofibers with Fe₃C decoration for water activation induced oxygen reduction reaction. National Science Review, 2024, 11(10): nwae193

[31] Yang N , Xue J R , Ji Y X , Zhang J Y , Zhang W Y , He X X , Li Q , Lei Z B , Liu Z H , Sun J . Self-supporting poly (3,4-ethylenedioxythiophene) and Fe₃C co-decorated electrospun carbon nanofibers as Li₂S supporters for lithium–sulfur batteries. Nanoscale, 2025, 17(13): 7877–7887

[32] Zhao Y X , Lai Q X , Wang Y , Zhu J J , Liang Y Y . Interconnected hierarchically porous Fe, N-codoped carbon nanofibers as efficient oxygen reduction catalysts for Zn-air batteries. ACS Applied Materials & Interfaces, 2017, 9(19): 16178–16186

[33] Wang J , Li B , Li Y , Fan X B , Zhang F B , Zhang G L , Peng W C . Facile synthesis of atomic Fe-N-C materials and dual roles investigation of Fe-N₄ sites in Fenton-like reactions. Advanced Science, 2021, 8(22): 2101824

[34] Lei G C , Zhao W T , Shen L J , Liang S J , Au C , Jiang L L . Isolated iron sites embedded in graphitic carbon nitride (g-C₃N₄) for efficient oxidative desulfurization. Applied Catalysis B: Environmental, 2020, 267: 118663

Rights & permissions

Higher Education Press