Preparation Of Transition Metal Ni-Co Based Phosphide(Sulfide) Composite Catalysts And Their Performances For Electrocatalytic Water Splitting

The goals of carbon peaking and carbon neutral are driving the transformation and upgrading of the energy industry.As a new energy source,hydrogen has the advantages of high energy density and zero carbon emission,which is ushering in an unprecedented strategic opportunity.Electrolytic water to hydrogen technology has become an important concern in sustainable development due to its easy operation process and environmentally friendly product characteristics,which is expected to reduce the impact of energy scarcity and environmental pollution.Although noble metal catalysts Pt,RuO₂ and IrO₂ are considered to be the most excellent catalysts for hydrogen and oxygen evolution reactions,their high production cost and scarcity hinder their scale-up applications.Therefore,there is a need to develop catalyst with high activity,good stability and low price for efficient water decomposition.Transition metals（Fe,Co,Ni,etc.）have the advantages of abundant elemental species,high reserves,low cost and high activity,and their oxides,hydroxides,phosphides,sulfides and other transition metal compounds have received wide attention from researchers in electrocatalytic hydrolysis.In this thesis,a series of Ni-Co-based phosphide and sulfide composite catalysts were designed and prepared,and their performance in catalytic HER,OER and electrolysis of water was investigated.The study includes the following three parts:1.Spinel NiCo₂O₄ was prepared by a hydrothermal and oxidation method.The reduction of NiCo₂O₄ by sodium borohydride resulted in the formation of B-NiCo₂O₄/NF in both crystalline and amorphous states,which provided abundant active sites for the reaction and facilitated the electron transport.B-NiP/CoP₂/NF was obtained by further phosphorylation of B-NiCo₂O₄/NF,which exhibited excellent electrocatalytic performance in 1.0 M KOH electrolyte.At the current density is 10 m A cm^-2,the OER and HER overpotential is 217 and 120 m V,and the voltage required for electrocatalytic water splitting is only 1.45 V.Meanwhile,the catalyst was able to operate stably for 40 h at a current density of 10 m A cm^-2,demonstrating high stability.2.A series of Cr-doped NiCoP catalysts were prepared by the solvothermal and phosphorylation method.Among them,the catalyst Cr-NiCoP-2/NF exhibited excellent bifunctional catalytic activity in 1.0 M KOH electrolyte at a Cr³⁺doping of 0.3 mmol.At a current density of 10 m A cm^-2,the overpotential of OER is 176 m V and that of HER is104 m V,and a cell voltage of 1.53 V is required for overall water splitting.At the same time,the catalysts exhibited excellent stability performance.3.CoFe-LDH@NiCo₂S₄/NF composite electrocatalysts with wrapped structures were constructed on nickel foam by a combination of solvothermal and electrodeposition.The catalyst showed excellent electrocatalytic activity in 1.0 M KOH electrolyte.At a current density of 10 m A cm^-2,the overpotential of OER and HER was only 187 and 136m V,and the cell voltage for overall water splitting was 1.54 V.In addition,the catalyst exhibits good stability.