Electroreduction of aqueous CO₂ is a sustainable approach to produce tunable syngas, which demands the rational design of dual-active-sites catalysts for individual CO₂ reduction reaction (CRR) and hydrogen evolution reaction (HER). Here, the self-supporting nickel@nitrogen-doped carbon nanotubes grown on carbon nanofiber (Ni@NCNTs-CNF) is developed with Ni single atoms (SAs) and nanoparticles (NPs) functioning as CRR and HER sites respectively. Benefiting from the hierarchical nanostructures for effective electron transport and mass diffusion, as well as the high accessibility of dual-active sites, Ni@NCNTs-CNF catalysts can mediate aqueous CO₂ into CO/H₂ (2:1) with a 100 % Faraday efficiency and a high current density (25 mA cm⁻²) at low working potential (-0.8 V). By manipulating the Ni SAs/Ni NPs ratio, the CO/H₂ proportion is easily modulated in a wide range from 1:4 to 5:1, independence of the working potential (-0.6 to -0.8 V). Our findings provide fresh insights into the design of dual-active-sites catalysts.

CO ₂水溶液的电还原是生产可调谐合成气的可持续方法，它要求针对单个CO ₂还原反应（CRR）和析氢反应（HER）合理设计双活性中心催化剂。在这里，在碳纳米纤维（Ni @ NCNTs-CNF）上生长的自支撑镍@掺杂碳纳米管被开发为分别具有Ni单原子（SAs）和纳米颗粒（NPs）充当CRR和HER位点。Ni @ NCNTs-CNF催化剂得益于有效的电子传输和质量扩散的分层纳米结构，以及双活性位点的高度可及性，可以将含水的CO ₂以100％的比例介导到CO / H ₂（2：1）中法拉第效率和高电流密度（25 mA cm^-2）在低工作电位（-0.8 V）下。通过控制Ni SAs / Ni NPs的比例，可以很容易地在1：4至5：1的宽范围内调节CO / H _2的比例，而不受工作电位的影响（-0.6至-0.8 V）。我们的发现为双活性中心催化剂的设计提供了新的见解。