Photoreduction of Iron(III) to Iron(0) Nanoparticles for Simultaneous Hydrogen Evolution in Aqueous Solution

Crystalline Fe nanoparticles were obtained with fluorescein (Fl) as the photosensitizer in triethylamine (TEA) or triethanolamine (TEOA) aqueous solution with FeCl3 as the Fe precursor under bright visible‐light light‐emitting diode (LED) irradiation. Photoinduced electron transfer from excited state Fl* and Fl− to Fe3+ produced the Fe nanoparticles, which served as the active catalyst for in situ photocatalytic hydrogen production with Fl and TEA or TEOA as the photosensitizer and electron donors, respectively, in the same system. Robust hydrogen production activities were observed under the Fe nanoparticle photoreduction conditions in basic solution, and tens of milliliters of hydrogen were obtained over prolonged LED irradiation. If inorganic support materials such as NH2‐MCM‐41 or reduced graphene oxide were introduced, dispersed nanoparticles with different sizes and shapes were deposited on the supports, which led to variously enhanced hydrogen production activities. The relationships between the morphologies of the Fe/H2N‐MCM‐41 or Fe/graphene composites generated in situ and the hydrogen production activities were investigated systematically. Shedding light on an iron catalyst: A bifunctional noble‐metal‐free system for the photoreduction of Fe3+ to Fe(0) nanoparticles in water and simultaneous highly efficient photocatalytic hydrogen evolution is established. The sizes of the Fe nanoparticles generated in situ are tuned by changing the sacrificial donor from triethylamine to triethanolamine and by the introduction of H2N‐MCM‐41 or graphene into the photocatalytic system.