Interface-stabilized high-valent Sn enables efficient CO2 electroreduction to formate/formic acid across the full pH range

• Published in: Nano energy 2024-11, Vol.130, p.110135, Article 110135
• Main Authors: Fan, Tingting, Zhang, Jiguang, Zhang, Xiaguang, Wang, Meng, Yi, Xiaodong, Lum, Yanwei, Chen, Zhou
• Format: Article
• Language: English
• Subjects: Electrochemical CO2 reduction; Full pH range; High-valent Sn; OCHO intermediate; SnOx/Cu6Sn5 interface
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2024.110135

The electrocatalytic synthesis of formate/formic acid (HCOO−/HCOOH) from CO2 can mitigate environmental issues and provide high-value-added products. Although tin oxide is an excellent catalyst for HCOO−/HCOOH production, it is easily reduced to its metallic state at high potentials, which decreases its activity. Additionally, tin oxide is challenging to stabilize in acidic electrolytes. Here, we introduced Cu to tin oxide catalysts to form Cu6Sn5@SnOx during the CO2 electroreduction process (CO2RR), achieving a high HCOO−/HCOOH Faradaic efficiency (88.4 % at 800 mA cm−2 in 1 M KOH electrolyte, 87.8 % at 300 mA cm−2 in 0.1 M H2SO4 electrolyte containing 1 M K+) and a maximum HCOO− partial current density (757.5 mA cm−2). The in situ spectroscopy and DFT calculations results revealed that the SnOx/Cu6Sn5 alloy interface plays a crucial role in stabilizing the surface high-valent Sn, which provides a thermodynamically stable environment for adsorbed *OCHO intermediate. This discovery offers new insights into the roles of each component in bimetallic catalysts in CO2 reduction. [Display omitted] •R-CuSnO3 has a core-shell structure with Cu6Sn5 as the core and SnOx as the shell.•In situ Raman measurements verify that high-valence Sn can exist stably during CO2 electrolysis.•The SnOx/Cu6Sn5 alloy interface helps stabilize surface high-valence Sn.•In situ ATR-IR measurements show that high-valence Sn favors *OCHO adsorption.•Cu6Sn5@SnOx exhibits excellent performance under both acidic and alkaline conditions.