Synthesis And Performance Of Hydrogen Oxidation/Evolution Electrocatalysts With Non-Carbon-Based Nitride Supports

In energy storage and conversion technologies,such as electrocatalytic water splitting and fuel cells,to improve the efficiency of energy conversion and reduce the reaction energy barrier,it is necessary for the design and synthesis of the electrocatalysts with high activity and excellent stability to reduce the overpotential of the reaction for practical requirement.The interactions between metals and supports could effectively regulate electronic structures of metals and improve catalytic performance of the catalysts.The selection of suitable supports and metals is the focus of research.In this dissertation,precious metal catalysts supported by the non-carbon-based nitrides have been prepared through wet chemical methods.The relationships between the microstructures of as-prepared catalysts and electrocatalytic performance of hydrogen oxidation/evolution have been systematically explored by a series characterization method.The main contents are as follows:1.Molybdenum nitride was chosen as the non-carbon-supports for Ir,the efficient electrocatalysts for hydrogen oxidation reaction under alkaline conditions have been developed through metal-support interactions between Ir and Mo₂N.The ultra-small Ir nanoclusters supported by one-dimensional Mo₂N nanowires has been obtained by calcining Mo O_x nanowire precursor containing Ir at high temperature under ammonia atmosphere.In the electrocatalyst,strong beneficial interactions between Mo₂N and Ir nanoclusters not only effectively limit the agglomeration of Ir nanoclusters,but also are beneficial for improving the intrinsic activity of the catalysts.The compositions,morphologies and structures of the as-prepared materials were well characterized by various test methods,and hydrogen oxidation reaction under alkaline conditions were also explored.The results have demonstrated that the interfacial electronic interactions between Ir and Mo₂N redistributes the charges in the interfacial region,leading to moderate hydrogen binding energy for hydrogen oxidation reaction.Ir-Mo₂N exhibits better mass-specific kinetic current density and mass-specific exchange current density than 20%Pt/C and 20%Ir/C under the alkaline conditions.2.Tungsten nitride was adopted as non-carbon-supports for Ru,the efficient electrocatalysts for hydrogen evolution reaction under p H-universal conditions have been developed through the metal-support interactions between Ru and W₂N.The"litchi"-shaped hollow Ru/W₂N catalysts were prepared through using ZIF-67 as nitrogen source and Ru-containing WO_x hollow spheres as precursors at high temperature calcination.The compositions,morphologies and structures of Ru/W₂N catalysts were characterized by various characterization methods,and hydrogen evolution reaction of Ru/W₂N under p H-universal electrolyte was systematically investigated.The results have demonstrated that the Ru/W₂N electrocatalyst exhibits small overpotential,low Tafel slope and excellent stability under p H-universal conditions,and the mass activity of Ru is better than that of commercial Ru/C,which is attributed that hollow structure could expose more active sites and is beneficial for mass transfer/diffusion.Meanwhile,the metal-support interactions regulate hydrogen adsorption free energy to suitable level,thus enhancing HER performance of Ru/W₂N.