Electrochemical Investigation of Potassium Iodide With Tetrabutylammonium Hexafluorophosphate in Photoelectrochemical Systems

A common supporting electrolyte, tetrabutyllhexafluorophosphate ammonium (TBAPF 6 ), exhibits unique electrochemical behavior when mixed with hole‐sacrificing agent potassium iodide (KI). In this work, a photoelectrochemical system with a sulfur‐based semiconductor Se‐CdS‐MPA photoelectrode is constructed for the mechanistic investigation of iodobutane production via KI and TBAPF 6 . The reaction can be carried out in both half‐cells, and factors such as the catalytic medium and external stimuli impact the iodobutane production rate. The overall iodobutane yield was 176.87 mol% after 10 h in both compartments of the system. Varying alkyl iodides are prepared through the reaction of ammonium ions with different alkyl chain lengths and iodide ions. Both the conversion and product yield increase with the elongation of alkyl chain length through an electron‐transfer‐controlled mechanism. The reaction proceeds spontaneously via S N 2 nucleophilic substitution, and the alkyl iodides are synthesized in conjunction with radical mechanisms under PEC conditions. The iodide ion also coupled with the cadmium ion from photo‐oxidative decomposition of the photoelectrode to constitute a new photocatalyst, CdI 2 , which improves the stability and photocurrent density of the system significantly. This work put forward a clear theoretical reference for the study of PEC and chalcogenide semiconductors.