NSRRC Activity Report 2023

032 NSRRC ACTIVITY REPORT 2023 unlikely that C–C coupling will occur in single-atom systems with only single-reactive sites. Additionally, during potential- driven conduction, such as in electrochemical CO 2 reduction, the atomic structure of active sites may undergo significant changes, resulting in unexpected and adaptive active states. Despite these efforts, a comprehensive understanding of the interplay between dynamic configurations and resulting product profiles on single-atom sites is still lacking. The teams of Hao Ming Chen (National Taiwan University) and Yen-Fa Liao (NSRRC) recently established a universal explication that reversibly low-coordinated configuration using X-ray absorption and X-ray emission spectroscopies (XES) at SP 12B1 and SP 12U1 , Taiwan beamlines in SPring-8. 2 By employing a complementary blend of in situ / operando methods, they present evidence of potential-driven restructuring in single-atom electrocatalysts, unveiling a dynamic activation that generates adaptive low-coordinated Cu centers. These centers exhibit significantly high activity toward CO production compared to the well-known four N-coordinated counterparts. It is evident that structural reconstruction, involving the dynamic breaking of Cu–N bonds, is partially reversible, while the formation of Cu–Cu bonds is distinctly irreversible. 3 To establish a general concept of dynamic low-coordinated atomic-electrocatalysts, various representative single-atomic electrocatalysts, including Fe, Co, Cu, and Zn, were prepared. Notably, in all single-atomic electrocatalysts, an essential threshold of atomic surface charge for efficient CO production was identified. This threshold was achieved only after the configuration transformation to generate a dynamic low-coordinated state, as their CO production remained almost inactive when the atomic surface charge was below this critical value. In summary, the observed CO production in the dynamic low-coordinated Cu configuration is nearly a hundred times higher than that in the 4N-coordinated counterpart. The atomic surface charge emerges as a paramount indicator for intrinsic activities in the CO 2 RR product profile. This concept is supported by the fact that low-coordinated Fe single-atomic electrocatalysts outperform those of Co and Cu single-atom catalysts, aligning with the findings in most reports. (Reported by Hao Ming Chen, National Taiwan University) This report features the work of Hao Ming Chen and Yen-Fa Liao, and their co-workers published in Nat. Commun. 14 , 5245 (2023). SP 12B1 Materials X-ray Study SP 12U1 Inelastic X-ray Scattering • X-ray Absorption Spectra, X-ray Emission Spectroscopy • Materials Science, Chemistry References 1. J. Wang, C.-S. Hsu, T.-S. Wu, T.-S. Chan, N.-T. Suen, J.-F. Lee, H. M. Chen, Nat. Commun. 14 , 6576 (2023). 2. C.-S. Hsu, J. Wang, Y.-C. Chu, J.-H. Chen, C.-Y. Chien, K.-H. Lin, L. D. Tsai, H.-C. Chen, Y.-F. Liao, N. Hiraoka, Y.-C. Cheng, H. M. Chen, Nat. Commun. 14 , 5245 (2023). 3. J. Wang, H.-Y. Tan, M.-Y. Qi, J.-Y. Li, Z.-R. Tang, N.-T. Suen, Y.-J. Xu, H. M. Chen, Chem. Soc. Rev. 52 , 5013 (2023).