Stepwise assembly of thiacalix[4]arene-protected Ag/Ti bimetallic nanoclusters: accurate identification of catalytic Ag sites in CO 2 electroreduction

• Published in: Chemical science (Cambridge) 2023-09, Vol.14 (37), p.10212-10218
• Main Authors: Tian, Yi-Qi, Mu, Wen-Lei, Wu, Lin-Lin, Yi, Xiao-Yi, Yan, Jun, Liu, Chao
• Format: Article
• Language: English
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/D3SC02793G

The accurate identification of catalytic sites in heterogeneous catalysts poses a significant challenge due to the intricate nature of controlling interfacial chemistry at the molecular level. In this study, we introduce a novel strategy to address this issue by utilizing a thiacalix[4]arene (TC4A)-protected Ti-oxo core as a template for loading Ag 1+ ions, leading to the successful synthesis of a unique Ag/Ti bimetallic nanocluster denoted as Ti8Ag8. This nanocluster exhibits multiple surface-exposed Ag sites and possesses a distinctive “core–shell” structure, consisting of a {Ti 4 @Ag 8 (TC4A) 4 } core housing a {Ti 2 O 2 @Ag 4 (TC4A) 2 } motif and two {Ti@Ag 2 (TC4A)} motifs. To enable a comprehensive analysis, we also prepared a Ti2Ag4 cluster with the same {Ti 2 O 2 @Ag 4 (TC4A) 2 } structure found within Ti8Ag8. The structural disparities between Ti8Ag8 and Ti2Ag4 provide an excellent platform for a comparison of catalytic activity at different Ag sites. Remarkably, Ti8Ag8 exhibits exceptional performance in the electroreduction of CO 2 (eCO 2 RR), showcasing a CO faradaic efficiency (FE CO ) of 92.33% at −0.9 V vs. RHE, surpassing the FE CO of Ti2Ag4 (69.87% at −0.9 V vs. RHE) by a significant margin. Through density functional theory (DFT) calculations, we unveil the catalytic mechanism and further discover that Ag active sites located at {Ti@Ag 2 (TC4A)} possess a higher ε d value compared to those at {Ti 2 O 2 @Ag 4 (TC4A) 2 }, enhancing the stabilization of the *COOH intermediate during the eCO 2 RR. This study provides valuable insights into the accurate identification of catalytic sites in bimetallic nanoclusters and opens up promising avenues for efficient CO 2 reduction catalyst design.