Every photoelectrochemical (PEC) measurement stands on three choices made before the first photon arrives: the working electrode, the reference and counter electrodes, and the cell. Get these right and the rest of the experiment is interpretation; get them wrong and no analysis recovers the data.
Photoelectrodes are films on conductive substrates, FTO glass is the standard. The film must adhere, cover uniformly and expose a defined area, mask everything else, an unmasked edge quietly enlarges the area and shrinks your reported current density. Record film thickness and active area; both belong in every paper.
Choose a reference suited to the electrolyte, Ag/AgCl for mild aqueous work, Hg/HgO for alkaline, and calibrate it against a known standard periodically. The counter electrode should not inject chemistry into the compartment: use a separated platinum anode for hydrogen-side work, or the cathode reaction will contaminate your measurement. Size the counter so it never limits the current.
The optical window, electrode spacing and stirrer position set both the photon flux at the film and the mass transport at its surface. Keep the window clean, the incidence angle fixed and the electrolyte depth constant. The same film in two different cells can report different photocurrents purely from geometry.
Start with dark scans, then chopped-light tests (on/off cycles) to see the true photoresponse and its transients, then linear sweep voltammetry under illumination. Chopped-light data reveals recombination and charging effects that steady sweeps hide.
Perfectlight supplies electrodes and complete PEC test systems; see solutions.
