The data is primarily electrochemical, acquired with the rotating ring disk electrode (RRDE) apparatus, as described in the manuscript. The RRDE technique offers a new approach in PSII studies because it allows for the real-time (∼ms) analysis of reaction pathways without the necessities of high currents (∼nA sensitivity) and bulk product accumulation. Briefly, the data was acquired with a potentiostat in a three or four electrode setup. The raw data files are converted into text. Photocurrent magnitudes are processed from raw data as well. The background dark current is subtracted to extract out photocurrent measurements. Additional experimental details are located in the experimental section at the end of the main text.