Electrocatalytic Oxidation Of Borohydride On Amorphous NiB Electrode Doped With Different Metals

Traditional energy resources are increasingly scarce,so it is urgent to develop a renewable energy to meet the sustainable development of modern society.Fuel cell is a clean,efficient and safe new type of power source.Direct borohydride fuel cells?DBFCs?fueled by sodium borohydride?alkaline solution?is the most promising energy installation in the future.In the abstract,the electron transfer value of sodium borohydride electro-oxidation can reach 8.However,considering that anodic oxidation and hydrolysis are preformed simultaneously,the oxidation reaction of sodium borohydride cannot be completely carried out.The hydrolysis reaction not only decreases the utilization of borohydride fuel but also causes safety problems.Therefore,finding a cost-effective and high-performance electrochemical anode catalyst is the key to the practicality of DBFCs.Amorphous materials,which possess the special features of more unsaturated atoms and long-range disorder,short-range order,resulting in their excellent catalytic properties.As one of the amorphous materials,Ni-based amorphous catalyst has received research attention,because of its simple preparation process and cost-effective.However,the catalytic activity of the Ni-based amorphous catalyst decreases when used as electrode catalytic material,due to its less uniformly dispersed with an extensive aggregation in some zones.The results of existing literatures have proved that adding a metal element is one of the most effective methods to improve the agglomeration phenomenon and increase the amorphous catalytic activity of Ni-based amorphous alloy.In this paper,we have tried to incorporate a second transition metal?Cu,Mo,Zn,Pt,Au?into NiB amorphous alloys and study the electro-oxidation performance of NiB/C catalyst modified by transition metal for BH₄^—,and investigated the effect of Cu and Mo addition on the electro-oxidation activity of BH₄^—,and deep analysed he mechanism of the electro-oxidation activity on NiB/C amorphous catalysts for BH₄^—.Firstly,we applied the chemical reduction method to prepare the Ni₁B_x?x=1,2,3,4?,Ni₁B₃M?M=Cu,Mo,Zn,Pt,Au?nanoparticles.The XRD and SEM physical characterization showed that Ni₁B_x?x=1,2,3,4?and Ni₁B₃M_0.03?M=Cu,Mo,Zn,Pt,Au?nanoparticles have spherical morphologies and are along to a typical amorphous structure.The average size of particles are approximately 50 nm.Compared with Ni₁B₃ nanoparticles,Ni₁B₃M_0.03?M=Cu,Mo,Zn,Pt,Au?nanoparticles have better dispersion.The electro-oxidation activity of the Ni₁B_x/C?x=1,2,3,4?and Ni₁B₃M_0.03/C?M=Cu,Mo,Zn,Pt,Au?nanoparticles was investigated by cyclic voltammetry?CV?,linear scan voltammetry?LSV?and electrochemical impedance spectroscopy?EIS?.The CV results showed that the electro-oxidation activity of Ni₁B_x/C nanoparticles initially increases and then decreases with the increase in B content.When the optimum molar ratio of nickel and boron is 1:3,the Ni₁B_x/C has the best electrocatalytic for BH₄^—oxidation.When the addition of Cu,Mo,Zn,Pt,Au can improve the electro-oxidation activity of Ni₁B₃/C catalyst,especially,the a trace amount of Cu or Mo has the significant effect on the catalytic activity of Ni₁B₃ M_0.03/C catalyst.Based on this,amorphous nanoparticles with different Cu or Mo contents were prepared in this paper,and detailed study the effect of Cu or Mo addition on the catalytic activity of Ni₁B₃/C.The electro-oxidation activity of the Ni₁B_x/C?x=1,2,3,4?and Ni₁B₃M_0.03/C?M=Cu,Mo,Zn,Pt,Au?nanoparticles was performed by cyclic voltammetry?CV?,linear scan voltammetry?LSV?,electrochemical impedance spectroscopy?EIS?and fuel cell test.The results showed that the content of Cu or Mo affects the electro-oxidation activity of Ni₁B₃/C for BH₄^—,and the electro-oxidation activity of Ni₁B₃Cu_x/C catalyst first increases and then decreases with the increase of Cu content,and the electro-oxidation activity of Ni₁B₃Cu_0.09/C catalyst is the highest.The results of LSV showed that the number of transferred electron of Ni₁B₃Cu_0.09/C catalyst is4.1.Based on the dates of EIS,The charge transfer resistance of the NiBCu_0.09/C catalyst is 4.937?cm²,which is 8 times higher than that of the Ni₁B₃/C catalyst.In fuel cell test,Ni₁B₃Cu_0.09/C catalyst has the maximum power density(128.75mW cm^-2).It is reveal that Cu can significantly improve the electro-oxidation activity of Ni₁B₃Cu_x/CSimilarly,the electro-oxidation activity of Ni₁B₃Mo_x/C catalyst initially increases and then decreases with the increase of Mo content,and Ni₁B₃Mo_0.05/C catalyst has the best electro-oxidation activity.The Ni₁B₃Mo_0.05/C catalyst has the maximum oxidation peak current density of 53.5mA cm^-2,and the corresponding maximum power density of 107.1 mW cm^-2.The addition to a second element?Cu or Mo?for NiB amorphous catalyst can significantly improve the electro-oxidation activity of Ni₁B₃/C.It may be caused by three factors:?1?Cu or Mo addition increases the value of ECSA for Ni₁B₃/C catalyst,which can increase the adsorption of more borohydride molecules on the catalyst surface.?2?The addition of Cu or Mo promote the electron transfer,making B electron-deficient and providing a synergy effect for Ni and B,which conducive for the adsorption of borohydride molecules.?3?The addition of Cu and Mo elements improves the agglomeration of the particles,increases the specific surface area of the catalyst,and exposes more active sites,which is conducive to the adsorption and oxidation of BH₄^—.In addition,the catalytic activity for borohydride oxidation is optimum when the molar content of Cu or Mo in the Ni₁B₃M/C catalyst is 2.2%or 1.5%.