pH- and Cation-Dependent Water Oxidation on Rutile RuO 2 (110)

• Published in: Journal of physical chemistry. C 2021-04, Vol.125 (15), p.8195-8207
• Main Authors: Rao, Reshma R., Huang, Botao, Katayama, Yu, Hwang, Jonathan, Kawaguchi, Tomoya, Lunger, Jaclyn R., Peng, Jiayu, Zhang, Yirui, Morinaga, Asuka, Zhou, Hua, You, Hoydoo, Shao-Horn, Yang
• Format: Article
• Language: English
• Subjects: Cations; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Interfaces; Molecules; Radiology; Redox reactions
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.1c00413

Noncovalent interactions at electrified interfaces are key to improving activity for the oxygen evolution reaction (OER). Here, we showed that on RuO2(110) in alkaline solutions, OER activity is cation-dependent, being largest in 0.1 M KOH compared to LiOH and NaOH. Using crystal truncation rod analysis, -O is detected on the coordinatively unsaturated site at 1.5 V-RHE in 0.1 M KOH, suggesting that the rate-determining step is -O + OH- → -OOH + e-, which is different from that in acid involving the final deprotonation of -OOH. The ordering of interfacial water in base was found to decrease with increasing potential and independent of cations. Using surface-enhanced infrared spectroscopy, the density of isolated water molecules (zero H-bonds) was found to increase, and the density of icelike water molecules (four H-bonds) decreases from Li+ to K+ at OER potentials. The higher activity of more isolated interfacial OH- ions in the case of K+ and the lesser stabilization of -O intermediates by hydration water of K+ compared to Na+ and Li+ can result in higher OER activity for KOH. This work provides molecular details of the interface as a function of potential and electrolyte and enables the design of more active electrochemical interfaces.