NSRRC Activity Report 2023

Chemical Science 029 the multi-dentate chelating effect of EDTA for enhancing CH 4 selectivity. Operando extended X-ray absorption fine structure (EXAFS) experiments conducted at the TLS 17C1 provided insights into the CuPc/CNP and EDTA/CuPc/ CNP catalysts. In Fig. 2(a) , the results show that the peak corresponding to the Cu–Cu metallic bond increased, while the Cu–N/O peak significantly decreased during CO 2 RR due to the reduction of Cu(II) and agglomeration. With EDTA decoration, the peaks corresponding to the Cu–Cu and Cu–N/O bonds showed slight increases and decreases, respectively. This indicates that EDTA, acting as a chelating agent, restrains the Cu ions, maintaining their structure and generating only small Cu clusters. The operando experiments demonstrated the chelating effect of EDTA on Cu ions, which influenced the chemical and physical properties of Cu species in the EDTA/CuPc/CNP during CO 2 RR, promoted CH 4 selectivity. Metal–organic frameworks (MOFs) are distinguished by numerous coordinative void spaces and high surface areas, making them potential candidates for CO 2 RR if a robust structure can be achieved. A copper-based MOF catalyst, Cu(OH)BTA (Cu atoms coordinating with deprotonated 1H-BTA and transversely connecting through hydroxyl groups), has been developed for CO 2 RR. 5 This catalyst achieved a Faradaic efficiency of 73% and a partial current density for C 2+ products of 365 mA cm −2 at 500 mA cm −2 . To investigate the Cu active sites of Cu(OH)BTA during CO 2 RR, operando XAS experiments were conducted at the TPS 44A ( Fig. 2(b) ). Operando XANES spectra identified that the Cu oxidation state remained unaltered throughout the entire potential range of CO 2 RR, while there was no discernible peak corresponding to the Cu–Cu metallic bond in the EXAFS spectra. This suggests that Cu maintained atomic dispersion in a coordinative manner throughout the CO 2 RR. In contrast, the XANES spectra of Cu(OH) BTA exhibited characteristics of metallic Cu within 10 min at 200 mA cm −2 under an Ar atmosphere. This underscores the robust nature of Cu(OH)BTA during CO 2 RR. In summary, the innovation of a flow cell for CO 2 RR represents a significant advancement that greatly enhances catalytic activity. Diverse catalyst designs can further regulate the selectivity and partial current density of the end product in CO 2 RR. This report highlights various design strategies, including enhancing conductivity with carbon nanotubes, stabilizing the Cu 0 /Cu + interface through nanograin boundaries, restricting Cu cluster size by incorporating EDTA and CNPs, and developing a robust MOFs catalyst. All these approaches demonstrated a notable improvement in selectivity and catalytic current density. The high current density observed in a highly reductive environment allows for the development of operando X-ray absorption spectroscopy within a flow cell, which replicates the electrocatalytic environment, providing an accurate reflection of the authentic catalyst TPS 44A setup of an Operando flow cell for X-ray absorption spectroscopy form. This approach helps elucidate the proper mechanisms for achieving highly efficient CO 2 RR. (Reported by Sung-Fu Hung, National Yang Ming Chiao Tung University) This report features the works of Sung-Fu Hung and his collaborators published in J. Mater. Chem. A 11 , 13217 (2023), ACS Nano 17 , 12884 (2023), Nat. Commun. 14 , 3314 (2023), and Nat. Commun. 14 , 474 (2023). TPS 44A Quick-scanning X-ray Absorption Spectroscopy TLS 17C1 EXAFS SP 12B1 Materials X-ray Study SP 12U1 Inelastic X-ray Scattering • XAS, RIXS • Materials Science, Chemistry References 1. S. F. Hung, F.-Y. Wu, Y.-H. Lu, T.-J. Lee, H.-J. Tsai, P.-H. Chen, Z.-Y. Lin, G.-L. Chen, W.-Y. Huang, W.-J. Zeng, Catal. Sci. Technol. 12 , 2739 (2022). 2. F.-Y. Wu, H.-J. Tsai, T.-J. Lee, Z.-Y. Lin, K.-S. Peng, P.-H. Chen, N. Hiraoka, Y.-F. Liao, C.-W. Hu, S.-H. Hsu, Y.-R. Lu, S.-F. Hung, J. Mater. Chem. A 11 , 13217 (2023). 3. Q. Wu, R. Du, P. Wang, G. I.N. Waterhouse, J. Li, Y. Qiu, K. Yan, Y. Zhao, W.-W. Zhao, H.-R. Tsai, M.-C. Chen, S.- F. Hung, X. Wang, G. Chen, ACS Nano 17 , 12884 (2023). 4. M. Fan, R. K. Miao, P. Ou, Y. Xu, Z.-Y. Lin, T.-J. Lee, S.-F. Hung, K. Xie, J. E. Huang, W. Ni, J. Li, Y. Zhao, A. Ozden, C. P. O’Brien, Y. Chen, Y. C. Xiao, S. Liu, J. Wicks, X. Wang, J. Abed, E. Shirzadi, E. H. Sargent, D. Sinton, Nat. Commun. 14 , 3314 (2023). 5. Y. Liang, J. Zhao, Y. Yang, S.-F. Hung, J. Li, S. Zhang, Y. Zhao, A. Zhang, C. Wang, D. Appadoo, L. Zhang, Z. Geng, F. Li, J. Zeng, Nat. Commun. 14 , 474 (2023).