Research On Design Synthesis And Electrocatalytic Performance Of Doped Transition Metal Borides

As a green and environmentally friendly secondary energy,hydrogen energy is a key subject of research in the energy era.Hydrogen production by electrolysis of water has become the most commonly used method for hydrogen production due to its high yield,high hydrogen production purity and convenient operation process.However,due to the slow reaction kinetics in the actual application process,electrocatalysts need to be added.At first,noble metal materials such as Ru,Ir,Pt were used as the first choice catalysts,which were limited by the few noble metal raw materials and high cost.Therefore,the development of non-precious metal catalyst materials has become the focus of research.Transition metal borides show excellent catalytic performance due to their special electronic structure,but at the same time,there are problems such as complex synthesis process and single function.Therefore,in this paper,doped transition metal borides are designed and synthesized,and their catalytic properties are studied and compared with noble metal materials,which provides a new research direction for the subsequent research of non-noble metal catalysts.The main research contents are as follows:（1）Synthesis of amorphous borides Ni-Fe-Co-B and electrocatalytic properties for oxygen evolution reaction.In the research of electrocatalysts,the catalysts mainly made of transition metals Ni,Fe,and Co are widely studied and have excellent performance.In this paper,transition metal Ni,Fe,Co salts were selected as raw materials,and sodium borohydride（Na BH₄）was used as B source,Amorphous ternary transition metal borides Fe-Co-B and quaternary transition metal borides Ni-Fe-Co-B were prepared by simple liquid phase synthesis as catalysts for oxygen evolution reaction.On the basis of the optimal metal ratio of ternary transition metal borides,another transition metal Ni was added to explore the optimal content of it.Through different characterization techniques,the successful synthesis of nanoscale amorphous catalytic materials is demonstrated,and it also shows that the materials have excellent catalytic performance due to the coupling effect between metals and the incorporation of B.The quaternary transition metal boride Ni-Fe-Co-B has an OER overpotential of only 299 m V and a Tafel slope of only 101 m V/dec at a current density of 20 m A/cm~2,and has excellent stability for more than 12 hours under constant voltage test,which provides an excellent choice for the subsequent research of transition metal borides as catalysts for electrolysis of water.（2）Synthesis and electrocatalytic properties of bimetallic boron phosphide.The catalytic performance of the material can be effectively improved by doping non-metallic atoms.It is found that transition metal borides and transition metal phosphides are excellent catalysts for oxygen evolution reaction and hydrogen evolution reaction.In this paper,transition metal boron phosphide is synthesized on the basis of transition metal boride by doping non-metal atom P.Select transition metal Ni and Fe salts as raw materials,sodium borohydride（Na BH₄）as B source,and sodium hypophosphite（Na H₂PO₂·1H₂O）as P source,The single-metal boron phosphide Ni-BP was synthesized by a simple liquid phase reaction,and the optimal ratio of B and P was explored.Under the optimal B,P ratio,another transition metal Fe was doped to synthesize the bi-metal boron phosphide Ni-Fe-BP,to explore the optimal ratio of bimetals.Through different characterization tests,the successful synthesis of nanoscale amorphous single-metal boron phosphide Ni-BP and bimetallic boron phosphide Ni-Fe-BP was demonstrated.The results showed that when the ratio of B to P is 1:5 and the iron content is 0.2,the catalytic performance of the material is the best.At a current density of20 m A/cm~2,the overpotential for oxygen evolution reaction is 310 m V and the overpotential for hydrogen evolution reaction is only 258 m V.Under the constant voltage test,it has excellent stability for more than 12 h.（3）Synthesis and electrocatalytic properties of bimetallic boron phosphide supported on carbon nanotubes.Carbon-based materials are considered as ideal catalyst supports due to their unique electronic structure and good electrical conductivity as well as high specific surface area.In this paper,multi-walled carbon nanotubes are selected as catalyst supports,Co,Ni transition metal salts are selected as raw materials,sodium borohydride（Na BH₄）as B source,sodium hypophosphite（Na H₂PO₂·1H₂O）as P source,The transition metal boride Co-Ni-B and transition metal boron phosphide Co-Ni-BP supported on carbon nanotubes were synthesized by a simple liquid-phase reaction.The experiments explored the optimal ratio of bimetals in Co-Ni-BP and the optimal concentration of multi-walled carbon nanotubes.The successful synthesis of amorphous Co-Ni-BP and Co-Ni-BP/MWCNT materials is demonstrated by different test characterizations.The results show that when the Ni content is 0.1 and the carbon nanotube concentration is 1 mg/m L,the Co-1Ni-BP/MWCNT₁catalyst has the best performance,showing the oxygen evolution reaction overpotential of 288 m V at a current density of 10m A/cm~2,and the hydrogen evolution reaction overpotential of 117 m V.The overall water splitting of the catalyst material was studied,and it was found that the current density of 10 m A/cm~2could be reached at 1.63 V,indicating that the synthesized Co-1Ni-BP/MWCNT₁catalyst material has bifunctional properties and has excellent electrochemical stability performance for more than 12 h.