A Series of Cobalt bis(Thiosemicarbazone) Catalysts for Effective Photocatalytic Hydrogen Evolution Reaction

In order to diminish environmental issues such as global warming due to increased carbo dioxide (CO2) emissions, considerable efforts have been made in the research community. Photocatalytic hydrogen (H2) production is a very important way towards this goal, since sunlight is an abundant source of energy and H2 is a clean fuel, producing no greenhouse gases. Inexpensive, stable and non-toxic carbon dots were easily synthesized and used as photosensitizers in water in the presence of a series of molecular cobalt catalysts (CoTSC). The catalysts were thiosemicarbazone-based complexes able to transfer electrons for hydrogen evolution reaction. Under visible light irradiation, the nitrogen-doped carbon dots (NCdots) transfer the photoexcited electrons to the catalyst, producing an activity of 358 & mu;mol gNCdot-1 h-1 (TONCo=570) for CoTSC-N(CH3)2CN after 24 h of irradiation. These types of molecular catalysts display great activity and stability in combination with the easily synthesized and modified carbon dot materials. An efficient photocatalytic system with earth abundant carbon dots and a series of cobalt thiosemicarbazone catalysts was designed and studied. All prepared photocatalysts produced hydrogen, reaching a rate of 358 & mu;mol gNCdot-1 h-1 upon light irradiation in water.+image