Adapting Pressurized Sample Infusion ESI‐MS for Real‐Time Monitoring of Heterogeneous Photoelectrocatalytic Reactions

Pressurized sample infusion (PSI) enables real‐time electrospray ionization mass spectrometric (ESI‐MS) monitoring of reactions through continuous delivery of solution from a pressurized vessel. Existing PSI configurations, however, are not well suited to systems involving heterogeneous catalysts with strict geometric demands, such as TiO 2 nanotube plates. Here, we describe a modified PSI configuration in which a standard media bottle fitted with a silicone septum replaces a multineck Schlenk flask. This design accommodates plate‐based catalysts that cannot be easily used in conventional PSI reactors (in this specific case, TiO 2 nanotube arrays), enables controlled pressurization via needle‐based gas injection, and permits insertion of capillary tubing for continuous sample infusion to the mass spectrometer. Rhodamine B was used as a model compound to monitor photocatalytic (PC) and photoelectrocatalytic (PEC) degradation under different reaction conditions. The approach enables straightforward real‐time mass spectrometric monitoring of PEC and PC systems employing heterogeneous catalysts.