In Situ Raman Spectroscopy Reveals the Multifunctional Role of Interfacial Water in CO2-to-C2 Electroreduction on
Yu Zhao1,2, Qiong-Qiong Li1, Quan-Feng He1,3
1College of Energy, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, College of Physical Science and Technology, Xiamen University, Xiamen 361005, China.
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Interfacial water serves as both a proton donor and a competitor for active sites at the copper-catalyst interface in the electrochemical CO2 reduction reaction (CO2RR). However, its precise impact on C2+ product selectivity remains debatable. Here, through the utilization of in situ Raman spectroscopy and theoretical calculations, we have discovered that the population of K+ cation hydrated water (K-H2O) rises concurrently with the increase of C2 yield on atomically flat model Cu(hkl) single crystal surfaces. The K+ not only stabilizes the *CO + *CO intermediate by direct coordination but also reshapes the configuration of solvated interfacial water to create a hydrogen-bond-absent environment. This prevents surrounding hydrogen from interacting with the *CO species, ingeniously suppressing its hydrogenation along the C1 pathway while promoting C-C coupling toward C2 products. Our results further clarify the CO2RR mechanism and provide definitive evidence that cationic hydrated water is critical to tuning the product selectivity.
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