Investigation On Preparation And Hydrogen/Oxygen Evolution Reaction Performance Of Fe-,Ni-,Pt-based Electrocatalysts

Electrolytic water splitting technology is a fresh hope to solve the current energy crisis,and it consists of two important half reactions,oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).In order to overcome the high energy barriers that restrict OER and HER,new efficient catalysts are the key.In this paper,we designed and prepared a variety of OER and HER catalysts through various synthetic methods,and explored their properties and physical mechanisms.1.Cu2O is an ideal template material for the preparation of transition metal hydroxide/oxyhydroxides,which have high OER catalytic performance.Inspired by Pearson’s principle,Cu2O wires were prepared and used as a sacrificial template to prepare Ni(OH)2·0.75H2O hollow tubes(Ni(OH)2 HTs)with highly improved surface roughness.Benefiting from its unique structural advantages,Ni(OH)2 HTs showed excellent catalytic activity,rapid kinetics and long-term stability as the OER catalyst.Therefore,this chapter provides a novel template-assisted strategy to prepare high-performance transition metal-based OER catalysts with hollow and tubular structures.2.On the basis of the last work,we further propose a new strategy to obtain onedimensional hollow micro-nano catalytic material:FeOOH micro-nano hollow tubes were prepared using Cu2O wire as template.Its surface presents scaly nanostructure,which further increased the specific surface area.When used as OER catalyst,the FeOOH scaly hollow tubes(FeOOH SHTs)also showed excellent catalytic performances.Meanwhile,after characterizing the microcosmic crystal structure and electronic structure of FeOOH SHTs,we found that the reasons for the excellent catalytic performances of FeOOH SHTs were the existence of highindex facets on the catalyst surface,the maintenance of high valence state,and so on.Then,we revealed the catalytic mechanism of lattice oxygen oxidation of FeOOH SHTs.Compared with the work in the last chapter,we further prepared FeOOH SHTs,a highly efficient OER catalyst with unique morphology,and studied deeply the catalytic mechanism of OER.3.Next,we explored another important half reaction of over water splitting,HER.Pt-Nb2O5 nanocomposite was successfully prepared by mercury lamp reduction in liquid system.Then,after characterizing the electronic structure of the composite,we found a charge transfer effect between Pt and Nb2O5,forming an electronic metal-support interaction(EMSI).This interaction makes the metal Pt which plays the main catalytic role form an electron-rich environment,improving the electron donating ability and the stabilization of adsorbed hydrogen for the catalyst and thus achieving enhanced electrochemical catalytic activity.Then,with the energy band diagrams,we discussed the heterostructure formed by this Schottky contact in detail.Benefiting from the EMSI and synergistic effect between Pt and Nb2O5,when 10%Pt-Nb2O5 nanocomposite was used as HER catalyst,it showed excellent catalytic performance.This work proposes an ideal synthesis method and designed efficient Pt-Nb2O5 catalytic material.At the same time,our analysis for the structureproperty relationship also has reference significance for the future study of the physical mechanism of Pt-based catalysts.4.In order to further explore the HER physical mechanism for metal-support heterostructure,Pt-MoS2 nanocomposite was synthesized by a simple wet chemical method.First,using transmission electron microscope,we analyzed and inferred that the monodisperse Pt nanoparticles modified on the 2H-MoS2 nanosheets have a half truncated octahedral atomic configuration that partially halved by the(011)crystal face,and that was confirmed by simulated image.Subsequently,the characterization of the electronic structure for Pt-MoS2 proves that the formation of Pt-S bonds and the electron transfer from Pt to MoS2,thus forming an EMSI.Under the EMSI and synergistic effects,Pt-MoS2 nanocomposite showed excellent catalytic activity and stability for HER.Finally,according to the constructed atomic model,we carried out the density functional theory(DFT)calculation.It theoretically confirms the charge transfer effect between Pt and MoS2,and also proves the formation of Pt-S bond,the order of Pt {1 1 1}<Pt {1 0 0} for HER activity on the Pt facets,and the stronger activity of Pt atom at the interface.This work deeply explored the relationship between EMSI and HER catalytic performance in heterostructures,and provides a necessary reference for the design of metal-support heterogenous catalysts with high HER properties.