Photoelectrochemical cells are usually designed to either generate hydrogen by electrolysis or to generate photocurrent, i.e., they can be analogous to photovoltaic cells, such as dyesensitized photoelectrochemical cells that make use of light-sensitive organic dyes (photosensitizers) for photocurrent generation. Other common applications of photoelectrochemical cells are taking advantage of the photocurrent polarity for sensing and logic operation. An important parameter in electrochemical processes is their dependence on the local pH, meaning the local concentration of protons next to the electrode. Here, we use Brønsted photoacids (PAs) and photobases (PBs) that can behave as strong acids and bases only as a response to light absorption, thus, they can transiently manipulate the proton concentration using light as an energy source. This property of PAs and PBs is due to their fundamental change in pKa that drops or rises, respectively, upon excitation, thus resulting in an excited state proton transfer (ESPT) event. Therefore, in their electronically excited state, a PA dissociates and transfers the proton to a proton acceptor, such as water or another solvated molecule, while a PB acts in a reverse mode by abstracting a proton from a proton donor, which similarly can be water or another donor. This ability of Brønsted PAs and PBs has been used before to transiently control dynamic processes that are dependent on the protonation or deprotonation of molecules, such as self-assembly processes, enzymatic activities, selfpropulsion, and protonic transport. It is worth mentioning that other types of molecules are also termed PAs, which are not the type used here, but rather a photochromic molecule that undergoes a light-induced structural change in which a proton is released, with the spiropyranmerocyanine system being the common representative of such PAs.