Preparation Of Iron-nickel Based Catalysts And Study Of Catalytic Water Decomposition Properties

With the rapid development of social economy,the energy crisis and environmental problems have become a worldwide problem.Therefore,researchers over the world are searching for a renewable alternative energy.Hydrogen,as a clean energy,has been recognized as the most promising green energy in the future.Among the current hydrogen production technologies,water splitting induced by electricity or light are among a few limited leading technologies to product H2.There are two half reactions involved in the waterspliting process,the first is cathodic hydrogen evolution reaction(HER)and the second anodic oxygen evolution reaction(OER).Both of them are implemented to reduce the large overpotentials and thus improve the production efficiency.Up to now,the most efficient catalysts for the HER or the OER are materials based on noble metal elements,while their scarcity and high costs have hindered their widespread applications.Therefore,it is imperative to develop alternative catalysts based on cheap elements for the HER and the OER for economical large scale production of the water waterspliting.In this work,we aimed at developing stable and efficient catalysts based on cheap transition metal elements Ni and Fe for HER and OER.Their catalytic application for the water splitting has been studied in detail.(1)A one-pot simple hydrothermal process was used to assemble cubic NiFe2O4 nanoparticles onto ?-Ni(OH)2 nanosheets without adding any mineralizer.A series of NiFe2O4/?-Ni(OH)2 composites can be produced by changing Ni/Fe molar ratio.The FeNi composites with Ni/Fe molar ratio of 5.0 presents the best catalytic activity,which achieves 10 mA cm-2 at overpotential of 0.34 V and has a Tafel slope 41 mV decade-1.The overpotential reduces while the OER kinetics stays unchanged as the increase of a-Ni(OH)2 content,which indicates that a-Ni(OH)2 affects the overpotential while NiFe2O4 mainly controls the OER kinetics.The obtained NiFe2O4/a-Ni(OH)2 composites is also a promising co-catalyst for the photocatalytic water oxidation with the oxygen generation rate of 34 ?mol g-1,even more active than the noble PtOx,as well as acceptable stability.(2)The sample dominated by NiS2,as well as a few amount of FeS2 can be prepared under themal sulfuration in a conventional two-zone horizontal tube furnace by taking NiFe2O4/a-Ni(OH)2 nanocompounds as precursor and sulfur powder as sulfur source,which is maked as Fe/NiS2.The Fe/NiS2 presents better HER catalytic activity than pure NiS2,achieving a current density of 10 mA cm-2 at an overpotential of 225 mV.In addition,Fe/NiS2 can be loaded onto CdS nanorods with the same method besides changing the precursor by NiFe-CdS mixture.The Fe/NiS2 provides HER active sites and inhibits photon-generated carriers recombination within CdS effectively,resulting in the condiderable photocatalytic hydrogen generation perfomance based on Fe/NiS2-CdS compound.