Reversibility of Ferri-/Ferrocyanide Redox during Operando Soft X-ray Spectroscopy

• Main Authors: Regier, Tom Z. (Author), Peak, Derek (Author), Sayed, Sayed Youssef (Author), Risch, Marcel (Contributor), Stoerzinger, Kelsey Ann (Contributor), Shao-Horn, Yang (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Materials Science and Engineering (Contributor), Massachusetts Institute of Technology. Department of Mechanical Engineering (Contributor), Massachusetts Institute of Technology. Research Laboratory of Electronics (Contributor)
• Format: Article
• Language: English
• Published: American Chemical Society (ACS), 2017-06-05T16:20:39Z.
• Subjects: Article
• Online Access: Get fulltext

The ferri-/ferrocyanide redox couple is ubiquitous in many fields of physical chemistry. We studied its photochemical response to intense synchrotron radiation by in situ X-ray absorption spectroscopy (XAS). For photon flux densities equal to and above 2 × 1011 s-1 mm-2, precipitation of ferric (hydr)oxide from both ferricyanide and ferrocyanide solutions was clearly detectable, despite flowing fast enough to replace the solution in the flow cell every 0.4 s (flow rate 1.5 mL/min). During cyclic voltammetry, precipitation of ferric (hydr)oxide was promoted at reducing voltages and observed below 1011 s-1 mm-2. This was accompanied by inhibition of the ferri-/ferrocyanide redox, which we probed by time-resolved operando XAS. Our study highlights the importance of considering both electrochemical and spectroscopic conditions when designing in situ experiments.