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Atomically dispersed and nitrogen-coordinated single Ni sites ( i.e. , NiN x moieties) embedded in partially graphitized carbon have emerged as effective catalysts for CO 2 electroreduction to CO. However, much mystery remains behind the extrinsic and intrinsic factors that govern the overall catalytic CO 2 electrolysis performance. Here, we designed a high-performance single Ni site catalyst through elucidating the structural evolution of NiN x sites during thermal activation and other critical external factors ( e.g. , carbon particle sizes and Ni content) by using Ni–N–C model catalysts derived from nitrogen-doped carbon carbonized from a zeolitic imidazolate framework (ZIF)-8. The N coordination, metal–N bond length, and thermal wrinkling of carbon planes in Ni–N–C catalysts significantly depend on thermal temperatures. Density functional theory (DFT) calculations reveal that the shortening Ni–N bonds in compressively strained NiN 4 sites could intrinsically enhance the CO 2 RR activity and selectivity of the Ni–N–C catalyst. Notably, the NiN 3 active sites with optimal local structures formed at higher temperatures ( e.g. , 1200 °C) are intrinsically more active and CO selective than NiN 4 , providing a new opportunity to design a highly active catalyst via populating NiN 3 sites with increased density. We also studied how morphological factors such as the carbon host particle size and Ni loading alter the final catalyst structure and performance. The implementation of this catalyst in an industrial flow-cell electrolyzer demonstrated an impressive performance for CO generation, achieving a current density of CO up to 726 mA cm −2 with faradaic efficiency of CO above 90%, representing one of the best catalysts for CO 2 reduction to CO.
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This content will become publicly available on October 17, 2026
Operando Elucidation of Filamentous Carbon Gasification Kinetics and Mechanisms on a Spent Ni/CeO 2 Catalyst
Coking is the leading cause of catalyst deactivation in many important hydrocarbon conversion technologies. Understanding regeneration mechanisms is critical for developing effective carbon removal strategies that improve catalyst longevity and reduce operational costs. Here, we present a spatially resolved operando investigation of the regeneration of a spent Ni/CeO2 catalyst under industrially relevant air-like conditions, using in-situ environmental transmission electron microscopy (ETEM) combined with semantic segmentation. By deconvoluting competing gasification events for filamentous carbon removal, we found three distinct gasification modes─while fast catalytic gasification was expected, less steady noncatalytic combustion and cooperative gasification were also present and even more prevalent. Microstructure-informed kinetics directly linked the maximum gasification rates to axial filament consumption through either Ni/carbon contact or filament breakage, emphasizing the pivotal role of edge-plane carbon sites across all gasification pathways. Moreover, our operando characterization uncovered a Ni(−Cx)-limited carbon diffusion mechanism, which challenges the conventional carbon bulk diffusion model typically assumed for catalytic gasification. Furthermore, adverse processes such as Ni/carbon contact disruption and gasification-induced catalyst sintering were also identified. Collectively, these findings provide mechanistic insights into carbon gasification processes, highlighting critical pathways and potential pitfalls that can guide the optimization of catalyst regeneration strategies.
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- Award ID(s):
- 2238213
- PAR ID:
- 10658131
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Catalysis
- Volume:
- 15
- Issue:
- 20
- ISSN:
- 2155-5435
- Page Range / eLocation ID:
- 17393 to 17406
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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