Photoelectrocatalytic Dioxygen Reduction Based on a Novel Thiophene-Functionalized Tricarbonylchloro(1,10-phenanthroline)rhenium(I).

A novel Re (I) complex of [Re(CO)Cl(L)], {L = 2-([2,2'-bithiophen]-5-yl)-1-phenyl-1-imidazo [4,5-][1,10]phenanthroline}, was synthesized, and its optical (UV-Visible absorption and emission spectroscopy), cyclovoltammetric and photoelectrochemical oxygen reduction properties were studied. The geometric and electronic properties were also investigated by density functional theory calculations. It was found that the ITO electrode coated with drop-casted [Re(CO)Cl(L)] film exhibited cathodic photocurrent generation characteristics. The illuminated film exhibited a maximum cathodic photocurrent up to 30.4 μA/cm with an illumination intensity of 100 mW/cm white light at a bias potential of -0.4 V vs. SCE in O-saturated electrolyte solution, which was reduced by 5.1-fold when thoroughly deoxygenated electrolyte solution was used, signaling that the electrode performed well on the photoelectrochemical oxygen reduction. The photo-electrocatalytic hydrogen peroxide production was proved with a maximum HO concentration of 6.39 μM during 5 h of the photoelectrocatalytic process. This work would guide the construction of more efficient rhenium-based photo(electro)catalytic molecular systems for O sensing, hydrogen peroxide production and other types of photoelectrochemical energy conversion and storage.