Preparation Of Co-based Catalysts And Their Application In NaBH₄ Hydrogen Production

In recent years,hydrogen energy has been regarded as an important substitute for non-renewable energy as a new type of clean energy with high energy density.In the current hydrogen production and storage methods,the use of high energy density sodium borohydride materials for hydrogen production has attracted wide attention from researchers.The key to hydrogen production from sodium borohydride hydrolysis is catalyst preparation.Noble metal catalysts have a good effect in the catalysis process,but they are expensive and cannot be applied on a large scale.The advantages of Co B catalysts,such as low preparation cost and good catalytic performance,have been used by many researchers in the research of hydrogen production by the hydrolysis of sodium borohydride.In this paper,four ternary alloy catalysts of Co-Bi-B,Co-Cr-B,Co-Mn-B and Co-Sn-B doped with transition elements were prepared by chemical reduction method.The element composition,surface morphology and valence of the prepared catalyst were characterized and analyzed by XRD,SEM-EDS and XPS.Through the use of the above-mentioned catalyst to carry out the experiment of catalytic sodium borohydride hydrolysis to produce hydrogen,the catalyst preparation temperature,the transition metal doping ratio and the reaction kinetic analysis of the catalyst were studied.The specific research content is as follows:(1)Co-Bi-B catalysts were prepared at the reduction temperature of 0?,25? and 50? respectively,and used to catalyze the hydrolysis of sodium borohydride to produce hydrogen.The results showed that the catalyst was prepared when the reduction temperature was 0?.The catalyst catalyst is the best,so 0? is selected for catalyst preparation in the experiment.(2)In the course of the experiment,the effect of the change of the mole ratio of the doped transition metal elements in the three-way catalyst on the surface morphology,electronic interaction and the rate of catalytic sodium borohydride hydrolysis for hydrogen production was systematically studied.Among them,the optimal ratio of catalytic activity of Co-Bi-B alloy catalyst doped with Bi is n(Bi): n(Bi+Co)= 10%;the optimal ratio of catalytic activity of ternary alloy catalyst doped with Cr is n(Cr): n(Cr+Co)=1%;the optimal ratio of catalytic activity of Co-Mn-B alloy catalyst doped with Mn is n(Mn):n(Mn+Co)=20%;doped with Sn The optimal ratio of catalytic activity of the Co-Sn-B alloy catalyst is n(Sn): n(Sn+Co)= 3%.The results show that doping with a certain amount of Bi,Mn,Cr and Sn can reduce the dispersion of the catalyst to reduce the agglomeration of magnetic particles and improve its catalytic activity in the hydrolysis of sodium borohydride.(3)As the temperature increases,the rate of the catalyst catalyzing the Na BH4 hydrolysis reaction increases.After the kinetic study of hydrogen production by hydrolysis,it is calculated that the activation energy of the Co-Bi-B catalyst for the hydrolysis of sodium borohydride is 38.97 k J/mol,and the activation energy of the Co-Cr-B catalyst for the hydrolysis of sodium borohydride is 27.054 k J/mol,the activation energy of the Co-Mn-B catalyst for the hydrolysis of sodium borohydride is 30.170 k J/mol,and the activation energy of the Co-Sn-B catalyst for the hydrolysis of sodium borohydride is18.717 k J/mol.The experimental results show that the improved catalysts have lower activation energy for catalyzing the hydrolysis of sodium borohydride to produce hydrogen.The increase in catalyst activity is not only caused by the doping of the third element to reduce the agglomeration of the catalyst,but also between the elements.The transfer of different electrons is related.