One of the techniques is scanning electrochemical microscopy (SECM), which probes local heterogeneous reaction kinetics and fluxes of generated species.  In traditional SECM analysis of photocatalysts, evaluation of the influence of radiation on the rate of studied reaction requires an additional dark background experiment.  Here, using SECM and an inverted optical microscope, we demonstrate the determination of O2 flux caused by light-driven photoelectrocatalytic water splitting.  Photocatalytic signal and dark background are recorded in a single SECM image.  The light-driven flux of oxygen is calculated by analysis of SECM image recorded in substrate generation/tip collection mode. 
SECM
Evaluation of local oxygen flux produced by photoelectrochemical hydroxide oxidation by scanning electrochemical microscopy.Several in-situ electrochemical approaches have been developed for performing a localized photoelectrochemical investigation of the photoanode.  One of the techniques is scanning electrochemical microscopy (SECM), which probes local heterogeneous reaction kinetics and fluxes of generated species. 
scanning electrochemical microscopy