Department of Materials Science and EngineeringIt has been attracting many attentions to develop a renewable, sustainable way to replace fossil-fuel based energy systems. Among the many candidates, hydrogen based energy systems have possibility of clean and secure future due to low-carbon society. Water splitting has huge potential for production of hydrogen in a clean way, for its source is water - renewable and nearly infinite source. However, it is only 4% portion in hydrogen production because of high cost and lack of industrial foundation. To deal with these problems, one of the solution is to develop the low-cost and highly efficient catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to replace the noble metals (Pt) and precious metal oxides (RuO2 and IrO2), respectively. Especially, it is important to consider charge transfer kinetics for developing effective electrocatalyst. In this viewpoint, two main strategy were used in this study. One is the nitrogen (N) doped graphene quantum dots functionalization of perovskite oxide for better OER electrocatalyst, the other is adding conductive copper (Cu) ions to nickel phosphide (Ni-P) as an effective bifunctional electrocatalyst for overall water splitting.
First N-doped graphene quantum dot functionalized LaxSr1-xCoO3 was synthesized as a highly active electrocatalyst for OER to deal with sluggish kinetics of OER, bottleneck for water splitting. Perovskite oxide ABO3 (A: alkaline or rare earth metal, B: transition metal) have been attracting many attentions due to flexible electronic structure, high activity descriptor, good stability, etc. Among them, LaxSr1-xCoO3 have received many attentions as a highly active catalyst. And applying N doped-graphene quantum dot is a promising way for engineering of perovskite oxide to build high-performance OER catalyst by controlling charge transfer in the catalyst.
Second, Cu-doped Ni-P was synthesized by electrodeposition for effective electrocatalyst for overall water splitting. The incorporation of Cu into the Ni-P is expected to improve the electrocatalytic performances because of the reduction of charge transfer resistance and opposite sign of adsorption energy with hydrogen on Cu compared with that of Ni. It could be functioned as bifunctional electrocatalyst for overall water splitting. Finally, moisture formed on the surface was removed effectively by using water splitting reactions, which convert water into volatile hydrogen/oxygen gases. It was realized by 2-dimensional device with interdigitated pattern coated with highly active electrocatalyst NiCu-P for water splitting.clos
