Catalytic Materials For Oxygen Reduction Reaction And Less Pb Perovskite Solar Cells

In recent years, global energy crisis and environmental pollution problems have captured substantial attentions. Either utilizing the existing fossil fuel in a more efficient and environmentally friendly way, or developing a new-type renewable energy, is an effective pathway to coping with the increasingly serious energy and environment issues. In this paper, we will demonstrate the investigations on the cathode catalysts of hydrogen-oxygen fuel cells (FCs) and light-absorbers of perovskite solar cells in details.FCs are a kind of generation devices that could convert the chemical energy of fuels directly into electrical energy. FCs has been applied in many fields owing to their high energy utilization efficiency, clean and green properties, and portability etc. However, the commercialization of FCs is seriously hindered by the utilization of expensive cathodic oxygen reduction reaction (ORR) catalyst Pt. It is imperative to develop alternative electro-catalysts to replace the conventional Pt. two-dimensional carbon materials especially the N-doped graphene (NG) are considered to be the most promising candidate for ORR by the virtue of its high surface area, superior electrical conductivity, excellent thermal stability, and exceptional mechanical properties. To the best of our knowledge, NG has exhibited good catalytic activity in alkaline medium versus poor catalytic activity in acidic medium. Aiming at this tough issue, we managed to adopt urea as the source of nitrogen and fabricate a series of NGs through the adjustments on the pyrolysis temperature of graphene oxide and urea. These new-type NGs were applied to ORR and various characterizations are carried out. It turns out that the nitrogen performs multiple forms of existence in these NGs and the pyrolysis temperature will affect the N distribution. NG with abundant structural defects and balanced N distribution exhibits remarkable catalytic activities for ORR in both alkaline and acidic media.The newly emerging perovskite solar cells (PSCs) is at the forefront of photovoltaic research. The power conversion efficiency (PCE) of PSCs has exceeded 20% and several breakthroughs has been achieved until now. However, the commercialization of the organic-inorganic hybrid lead halide PSCs suffers from the limitation that the utilization of Pb will make people poison because of its biological accumulation in human body as well as will pose environmental hazards. Therefore, it’s imperative to develop new-type PSCs with less or no Pb. In order to keep the three-dimensional structure of perovskite, we adopted equivalent Sr ions of which the ionic radius is closed to that of Pb irons to partly replace the Pb ions. Consequently a series of Pb-less CH3NH3SrxPb(1-x)I3 perovskite were applied as light-absorber into PSCs for photovoltaic research. We systematically investigated the impacts of Sr doping on the crystallinity, morphology, light absorption, and photovoltaic performance of perovskite film. It’s demonstrated that the partly replacement of Pb ions had negligible effect on the crystallinity of original perovskite, while the surface coverage of mesoporous TiO2 layer with perovskite film was significantly improved. Compared with CH3NH3PbI3, CH3NH3Sro.3Pbo.7I3 performed intensive light absorption in visible region but the corresponding PCE is inferior.