Modulating Spin Behavior Of Inorganic Solids And Their Electrocatalysis Applications

Inherent properties of electrons,including charge and spin properties,have profound impacts on intrinsic characteristics in inorganic solids,such as electrical,magnetic,and optical properties.On the one hand,electronic spin provides new degree of freedom to modulate tranditional microelectronic devices based on electronic charge and promote the development of spintronics,which injects new impetus for information industry.On the other hand,electronic spin has significant influence for bonding between atoms,which can change the adsorption of molecules on catalytic surface and regulate dynamics during a catalytic process.Therefore,spin modulation in inorganic solids is not only the inevitable demands for in-deep understanding of our world,but also important methods for optimizing functional applications.In this dissertation,with correlated inorganic solids as the research object,electronic spin are effectively modulated via the coupling between spin and multiple degrees of freedom,especially charge,orbit and lattice.In this paper,effects of spin behaviros on electric transport,magnetism and electrochemical OER catalytic performance are highlighted.Spin behaviors in correlated inorganic solids are modulated by charge engineering,dimensional confinement,size engineering and coordination engineering,along with new physical phenomenon and enhanced electrochemical catalytic performance.The main content of this dissertation is summarized as following:1.Li+ions were intercalated into layered insulator ZrNCl for charge regulation.When Li ions entered the interplace of ZrNCl layers,charge was injected into the layer and induced superconducting transition.Meanwhile,charge injection also induced the generation of Zr3+ with net spin.Therefore,supercoductivity-ferromangetism coexsitence came into being in LixZrNCI.Besides,magnetotransport of LixZrNCl reveals a transition from positive magnetoresistance effect to large negative magnetoresistance effect,which proveide potent evidence for the coexistence of supercoductivity and ferromangetism.Frustrated phase separation of Li+ions and electronic separation in ZrNCl layer gave reasonable explanation for the spin related physical phenomenon.This work discovers charge regulation in ZrNCl can not only induce the generation of superconductivity,but also have profound impacts in the formation of ferromagnetism.The findings provide new views for comprehending the superconducting origination and mechanism in special two-dimentional supercondcutor LixZrNCl.2.Ultrathin Mn3O4 nanosheet was designed via topochemical synthesis to overcome the lack of intrinsic two-dimentiaonal ferromagnets.Strong magnetocrystalline anisotropy of Mn3O4 nanosheet was suggested by anisotropic magnetic measurement and supported it to be a kind of 2D ferromagnet.The easy axis of 2D Mn3O4 is tilted compared with its bulk counterpart.Two possible reasons are proposed to explain the spin tilting.On the one hand,dimensional confinement destroys the long-range magnetic ordered structure along[100]direction.On the other hand,the anisotropy energy caused by the broken symmetry on the surface of two-dimensional Mn3O4 nanosheet makes the magnetization tend to be along the out-of-plane direction.2D Mn3O4 with robust intrinsic two-dimensional ferromagnetism is an example of topochemical design for realizing 2D ferromagnet.3.Vibronic superexchange interaction is induced by size engineering in double perovskite La2NiMnO6 and it optimize eg electron filling-state of Ni and Mn.Vibronic superexchange interaction in La2NiMnO6 nanoparticle brings the optimal eg electron filling-state of Mn and Ni ions towards unity and induces strong Jahn-Teller distortion of MnO6 and NiO6 octahedronw with elongated metal-O bonds,which helps to form the active species of Mn/Ni hydroxide/oxide on the surface of catalysts.La2NiMnO6 nanoparticle exhibits superior OER catalytic performance with higher current density and lower Tafel slope than its bulk counter-part.This work promotes the study in advanced electrochemical OER catalsts via coupling effect between spin state and crystalline structure in correlated system.4.A mild chemical oxidation method was utilized to realize ligancy engineering in strongly correlated brownmillerite Sr2Co2O5 to perovskite phase Sr2Co2O5.5 with abundant oxygen vacancies.Due to the destruction of antiferromagnetic ground state,electronic transfer is greatly accelerated.At the meanwhile,active species of Co hydroxide/oxide emerged on the surface during the oxidation process.Unimpeded electron transfer and fast catalytic dynamics boost the OER performance.This work displays significant factor of coupling effect between multiple physical degrees of freedom for high-efficient OER catalysts.