To explore the expanse of bimetallic space for in situ nanoparticle synthesis, the concentration of two different precursor salts were varied in each column and row of a high-throughput photoreactor. Each vial comprised [Ir(Fmppy) 2 dtbbpy]PF 6 photosensitizer at 0.25 mM concentration, 400 µL of DMSO (J.T. Baker JT9224), 40 µL of a 30 percent (w/w) aqueous TEOA (Alfa Aesar L04486) solution, and metal salts at concentrations varying between 0.05 and 0.65 µM. Experiments included the metals Ag, Al, Au, Bi, Co, Cr, Eu, Fe, Ga, In, Ir, La, Li, Mn, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru, Sn, V, and Zn. A list of metal salt precursors is given in the Supporting Information. Reaction wells were illuminated over blue LEDs in a parallelized reactor setup as described previously. Using colorimetric chemosensitive H 2 detection tape (DetecTape Hydrogen Detection Tape-Midsun Specialty Products, Item DT-H210015-PF4), the reactions were tracked in real-time using image analysis to reveal the quantity of hydrogen produced by each. Calibrations for this method can be found in our previous work .