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Deprotonated 2-thiolimidazole serves as a metal-free electrocatalyst for selective acetylene hydrogenation



Metal-free catalysts offer a desirable alternative to traditional metal-based electrocatalysts. However, metal-free catalysts, featuring defined active sites, rarely show activities as promising as metal-based materials. Here we report 2-thiolimidazole as an efficient metal-free catalyst for selective electrocatalytic hydrogenation of acetylene into ethylene. Under alkaline conditions, the sulfhydryl and imino groups of 2-thiolimidazole are spontaneously deprotonated into dianions. Deprotonation thus enriches the negative charges of pyridinic N sites in 2-thiolimidazole to enhance the adsorption of electrophilic acetylene through the σ-configuration. Ethylene partial current densities show a volcano relationship with the negative charges of the pyridinic N sites in various imidazole derivatives. Consequently, the deprotonated 2-thiolimidazole exhibits an ethylene partial current density and faradaic efficiency competitive with metal-based catalysts like Cu and Pd. This work highlights the tunability and promising potential of metal-free molecules in electrocatalysis.

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Fig. 1: Comparison of electrocatalytic performance for 2TIm and metal-based electrocatalysts in a three-electrode flow cell.
Fig. 2: Electrocatalytic acetylene semihydrogenation catalysed by 2TIm in a two-electrode flow cell.
Fig. 3: Mechanistic investigations.
Fig. 4: Mechanistic studies with different imidazole derivatives.

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Data availability

The data that support the findings of this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.


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This work was financially supported by the National Natural Science Foundation of China (52373308 (J.Z.), 22005245 (J.Z.), 52101271 (L.Z.) and 22202123 (Z.W.)), the Key Research and Development Program of Shaanxi Province (2023-YBGY-284 (J.Z.) and 2024GX-YBXM-379 (L.Z.)), the Fundamental Research Funds for the Central Universities (G2022KY0606 (J.Z.) and G2020KY05306 (L.Z.)) and the Guangdong Basic and Applied Basic Research Foundation (2020A1515111017 (L.Z.)). We thank C. Liu at Shanxi University for help with the simulations.

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Authors and Affiliations



L.Z. and J.Z. conceived and designed the experiments. J.Z. supervised the project. L.Z. and R.B. carried out experiments and analysed the results. J.L. and Z.L. performed the characterization of the catalyst. J.B. optimized the electrochemical and product analysis set-ups. S.A. contributed to the electrochemical measurements. Z.W. conducted the grand canonical calculations. L.Z. and J.Z. assembled the figures and cowrote the manuscript. All authors discussed the results and commented on the paper.

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Correspondence to Zhihong Wei or Jian Zhang.

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Nature Chemistry thanks Liang Yu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Zhang, L., Bai, R., Lin, J. et al. Deprotonated 2-thiolimidazole serves as a metal-free electrocatalyst for selective acetylene hydrogenation. Nat. Chem. 16, 893–900 (2024).

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