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.

无金属催化剂为传统金属基电催化剂提供了理想的替代品。然而，具有明确活性位点的无金属催化剂很少表现出像金属基材料那样有前景的活性。在这里，我们报道 2-硫代咪唑作为一种有效的无金属催化剂，用于乙炔选择性电催化加氢成乙烯。在碱性条件下，2-硫代咪唑的巯基和亚氨基自发地去质子化成二价阴离子。因此，去质子化富集了2-硫代咪唑中吡啶N位点的负电荷，从而通过σ构型增强了亲电子乙炔的吸附。乙烯分电流密度与各种咪唑衍生物中吡啶N位点的负电荷表现出火山关系。因此，去质子化的2-硫代咪唑表现出与铜和钯等金属基催化剂相媲美的乙烯分电流密度和法拉第效率。这项工作强调了无金属分子在电催化中的可调性和有前景的潜力。