Lu Shanshan, Zhang Zhipu, Cheng Chuanqi, Zhang Bin, Shi Yanmei
Department of Chemistry, Institute of Molecular Plus, School of Science, Tianjin University, 300072, Tianjin, China.
Angew Chem Int Ed Engl. 2025 Jan 2;64(1):e202413308. doi: 10.1002/anie.202413308. Epub 2024 Oct 22.
M-N-C-type single-atom catalysts (SACs) are highly efficient for the electrocatalytic oxygen evolution reaction (OER). And the isolated metal atoms are usually considered real active sites. However, the oxidative structural evolution of coordinated N during the OER will probably damage the structure of M-N-C, hence resulting in a completely different reaction mechanism. Here, we reveal the aggregation of M-N-C materials during the alkaline OER. Taking Ni-N-C as an example, multiple characterizations show that the coordinated N on the surface of Ni-N-C is almost completely dissolved in the form of NO , accompanied by the generation of abundant O functional groups on the surface of the carbon support. Accordingly, the Ni-N bonds are broken. Through a dissolution-redeposition mechanism and further oxidation, the isolated Ni atoms are finally converted to NiOOH nanoclusters supported by carbon as the real active sites for the enhanced OER. Fe-N-C and Co-N-C also have similar aggregation mechanism. Our findings provide unique insight into the structural evolution and activity origin of M-N-C-based catalysts under electrooxidative conditions.
M-N-C型单原子催化剂（SACs）对电催化析氧反应（OER）具有高效性。并且孤立的金属原子通常被认为是真正的活性位点。然而，在OER过程中配位N的氧化结构演变可能会破坏M-N-C的结构，从而导致完全不同的反应机理。在此，我们揭示了碱性OER过程中M-N-C材料的聚集情况。以Ni-N-C为例，多种表征表明，Ni-N-C表面的配位N几乎完全以NO的形式溶解，同时在碳载体表面生成大量的O官能团。相应地，Ni-N键断裂。通过溶解-再沉积机制以及进一步氧化，孤立的Ni原子最终转化为以碳为载体的NiOOH纳米团簇，作为增强OER的真正活性位点。Fe-N-C和Co-N-C也具有类似的聚集机制。我们的研究结果为电氧化条件下基于M-N-C的催化剂的结构演变和活性起源提供了独特的见解。
