The Well Stirred Liquid Phase Photochemical Reactor: Laboratory Tool or Master of Disguises?

Abstract Since the early 1980s, liquid phase kinetic studies of homogeneous and heterogeneous photochemistry (especially including photocatalysis), have routinely utilized well stirred laboratory scale photoreactors. Convenient as these reactors are, their operation may be limited by reactant concentration, or by a transport limitation for light flux or dissolved oxygen. Similarly, the mechanistic interpretation of most phootocatalyzed liquid phase data has assumed the validity of Langmuir-Hinshelwood kinetics, whereas recent papers have demonstrated decisively that a pseudo steady state prevails, rather than equilibrium adsorption circumstance. We briefly review these circumstances which have led to kinetic disguises, and offer simple recommendations for future homogeneous and heterogeneous photochemical liquid phase studies which will allow determination of true rate constants and avoid the transport phenomena and mechanistic disguises evident in prior work.