Preparation And Electrocatalytic Performance Of Transition Metal-based-Ultrathin Two-Dimensional Nanomaterials

With the development of age,electrocatalysis technology has become one of the most effective strategies to solve environmental and energy problems,but excellent electrocatalyst is utilized to promote the whole electrocatalytic process.Transition metals and its derivatives have been regarded as ideal alternatives to noble metal such as Pt,Ru because of their rich content,low cost and good catalytic performance.Especially,the transition-metal-based ultrathin two-dimensional（2D）nanomaterials with unique microscopic morphology and unexpected electronic properties,possess a great application prospect in the field of electrocatalysis.It is well known that the electrocatalytic performance is closely related to the microstructure of electrocatalysts.However,there are few reports on the relationship between microstructures and electrocatalytic activities.In view of the above problems,this work adopts the transition metal ultra-thin 2D nanomaterials as promising research models to specifically study the influence mechanism of microstructures during the electrocatalytic process.The main contents include:（1）we have successfully prepareda-Ni（OH）₂-Ni₃S₄ hybrid structures as efficient electrocatalysts for methanol oxidation via a facile microwave-assisted in situ sulfidation strategy.Furthermore,the effect ofa-Ni（OH）₂-Ni₃S₄ hetero-interfaces on the MOR performance has been investigated by virtue of theoretical calculations and experimental observations,which demonstrated that the presence of abundant hetero-interfaces is conducive to both the formation of activeg-NiOOH species and the methanol molecule adsorption,leading to favorable anodic oxidation kinetics for the MOR.As a result,these hybrid structures exhibit a significantly promoted electrocatalytic MOR activity.This work not only offers new insights into the role of hetero-interface in improving the MOR efficiency,but also paves the way for the design of robust and efficient electrocatalysts for energy storage and conversion.（2）Transition metals layered double hydroxides（LDHs）with 2D structures,especially for NiFe-based LDHs nanosheets have been extensively explored and demonstrated as promising oxygen evolution reaction（OER）electrocatalysts for water splitting.However,traditional synthetic approaches for these advanced catalysts usually involve tedious pretreatment procedures and subsequent time-consuming exfoliation process,and the obtained products possess a wide dispersion of thickness and limited production yield.Here,we present a rapid room-temperature method to prepare a sequence of ultrathin NiFe-LDHs nanosheets with tunable components on a large scale under ambient conditions.Due to the synergetic effect of more exposed active sites,effective electron transport and optimal structural constituents,the resulting LDHs samples manifest outstanding electrocatalytic performance toward water oxidation.This work opens up a new method for the synthesis of LDHs with ultrathin 2D structure,which provides a great potential for the industrialization of water electrolysis in the future.（3）In this work,we demonstrate a novel synthetic strategy for the proof-of-concept Ni-Ni（OH）₂nanosheets electrocatalyst,which has been taken as a catalytic model to investigate the effect of Schottky heterojunction on the urea oxidation reaction（UOR）.The Ni-Ni（OH）₂nanosheets are prepared by in partial reduction of Ni（OH）₂ nanosheets to metal Nithrough an in situ topotactic transformation strategy,during which the typical nanosheet morphology is well reserved redering plenty of Schottky junction on the surface of electrocatalyst.Due to the different Fermi levels between the metal and semiconductor,the electron can spontaneously flow through the Ni-Ni（OH）₂heterointerface to form the Janus charge distribution.Benefitting from synergetic effects of high active surface area,fast charge transfer and promoted catalytic kinetics for UOR,the obtained Ni-Ni（OH）₂ nanosheets electrocatalyst shoes largely improved UOR performance in comparison with the pure Ni（OH）₂ nanosheets.This work,provides a promising approach for developing the non-noble highly efficient UOR catalyst.