Synthesis And Electrocatalytic Oxygen Evolution Properties Of LaCoO₃/Ti₃C₂T_x Composites

Electrochemical water splitting has gained significant attention to solve the ever-increasing energy demand and environmental contamination.Water electrolysis has two half-reactions of water electrolysis,which are hydrogen and oxygen evolution reaction?HER/OER?.Owing to the sluggish kinetics and complex four-electron process of?OER?in electrolytes,the OER is the most demanding.For these reasons,the OER is viewed by consensus to be the key to water electrolysis.In order to reduce the energy barrier and accelerate the OER,efficient and stable electrocatalysts are necessary.Perovskite-based electrocatalysts are one of the most promising materials for OER,but their activity and durability are still far from desirable.Therefore,LaCoO₃/Ti₃C₂T_x composite with excellent electrocatalytic activity was prepared by ball milling.Firstly,single-layer or few-layer Ti₃C₂T_X was synthesized by ball milling organ-like Ti₃C₂T_x using urea as intercalation agent,which can significantly improve the yield.The microstructure,composition and chemical state of single-layer or few-layer of Ti₃C₂T_x are characterized by XRD,TEM,AFM and other techniques.The results show that 300 rpm of ball milling speed is not enough to open the layers of organ-like Ti₃C₂T_x,while single-layer or few-layer Ti₃C₂T_x is successfully synthesized by 600 rpm.And the layer distance of Ti₃C₂T_x and the thickness of the single layer is about 1.3 nm and 1.5 nm,respectively.The material of grinding balls has no obvious influence on the stripping results.The single-layer or few-layer Ti₃C₂T_x obtained by zirconia ball is basically pure phase,but that obtained by steel ball is loaded with 3 nm Fe nanoparticles and 5 nm Fe3C nanoparticles.Secondly,the model of Fe single atom doping Ti₃C₂O₂ is established.It is proved that Fe single atom can exist stably in Ti₃C₂O₂ via the first principle calculation and d-band center.And the conductivity of Ti₃C₂O₂ doping Fe single atom is more excellent.The ORR performance of single-layer or few-layer Ti₃C₂T_x obtained by steel ball was tested by cyclic voltammetry,and the ORR peak appears at 0.6 V.Finally,LaCoO₃/Ti₃C₂T_x composites were prepared by ball milling.The morphology of LaCoO₃/Ti₃C₂T_x composite is single-layer or few-layer Ti₃C₂T_x coated with LaCoO₃.The increase of the valence state of Co indicates the strong interaction between LaCoO₃ and Ti₃C₂T_x and the electrons transfer from LaCoO₃ to Ti₃C₂T_x.When the mass ratio of LaCoO₃/Ti₃C₂T_x is 1:1,the OER reaction rate determination step changes from-OH rearrangement at the adsorption site to-O adsorption.The resulting hybrid material was applied in the oxygen evolution reaction and achieved a current density of 10 mA cm^-2 at a potential of 1.65 V vs reversible hydrogen electrode,and a Tafel slope of 47.1 mV dec-1 in 1 M NaOH.And its OER catalytic performance is the best among the series of materials.The electrically conductive and hydrophilic Ti₃C₂T_x nanosheets enable the rapid charge and ion transfer across the well-defined LaCoO₃/Ti₃C₂T_x interface and facilitated the access of aqueous electrolyte to the catalytically active LaCoO₃ surfaces...