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Ammonia is an effective feedstock for chemicals, fertilizers, and energy storage. The electrocatalytic nitrogen reduction reaction (NRR) is an alternative, efficient, and clean technology for ammonia production, relative to the traditional Haber−Bosch method. Singlemetal catalysts are widely studied in the field of NRR. However, very limited conclusions have been made on how to precisely modulate the coordination environment of the single-metalatom sites to boost catalytic NRR performance. Herein, we report a 5,7-membered carbon ringinvolved porous carbon (PC) preparation toward single-atom Ru-embedded PCs. As electrocatalysts, such materials exhibit surprisingly promising catalytic NRR properties with an NH 3 yield rate of up to 67.8 ± 4.9 μg h −1 mg cat −1 and a Faradaic efficiency of 19.5 ± 0.6%, exceeding those of most of the reported single-atom NRR catalysts. Extended X-ray absorption fine structure demonstrates that the presence of topological defects increases the Ru−N bond from 1.48 to 1.56 Å, modulating the coordination environment of the single-atom Ru active sites. Density functional theory-calculated results demonstrate that the adsorption of N 2 onto single-atom Ru surrounded by topological defects extends the N�N bond to 1.146 Å, weakening the strength of N�N and making it susceptible to the NRR. All in all, this work provides a new design strategy by involving topological defects and corresponding large polarization around the Ru single atom to boost the catalytic NRR performance. Such a concept can also be applied to many other kinds of catalysts for energy storage and conversion.

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Ammonia (NH 3 ) is a key component in fertilizers, plastics, medicine, and many other chemical products. [1] Since 1908, the dominant method of industrial large-scale ammonia synthesis has been the Haber-Bosch process, which requires extreme conditions (temperature: 400-500 °C, pressure: 200-300 atm) and consumes a tremendous amount of energy (1% of total worldwide power consumption [2] ). Greenhouse gas emissions, the ineffective conversion rate of raw material, and complex and costly equipment maintenance have meant the unsustainability of the Haber-Bosch process. [2,3] Even high-efficiency ammonia production that was using potassium-hydride-intercalated graphite [4] at 250-400 °C and 1 MPa in a home-built, fixed-bed reactor also consumes considerable power. The clean-energy-driven ENRR is a potential candidate to replace Ammonia is a key chemical feedstock worldwide. Compared with the wellknown Haber-Bosch method, electrocatalytic nitrogen reduction reaction (ENRR) can eventually consume less energy and have less CO 2 emission. In this study, a plasma-enhanced chemical vapor deposition method is used to anchor transition metal element onto 2D conductive material. Among all attempts, Ru single-atom and Ru-cluster-embedded perovskite oxide are discovered with promising electrocatalysis performance for ENRR (NH 3 yield rate of up to 137.5 ± 5.8 µg h −1 mg cat −1 and Faradaic efficiency of unexpected 56.9 ± 4.1%), reaching the top record of Ru-based catalysts reported so far. In situ experiments and density functional theory calculations confirm that the existence of Ru clusters can regulate the electronic structure of Ru single atoms and decrease the energy barrier of the first hydrogenation step (*NN to *NNH). Anchoring Ru onto various 2D perovskite oxides (LaMO-Ru, MCr, Mn, Co, or Ni) also show boosted ENRR performance. Not only this study provides an unique strategy toward transition-metal-anchored new 2D conductive materials, but also paves the way for fundamental understanding the correlation between cluster-involved single-atom sites and catalytic performance.