Preparation Of Cobalt-based Metal Catalysts And Study On The Performance Of Electrolyzed Water

Hydrogen production by water electrolysis is considered to be one of the most hopeful alternatives to traditional fossil fuels.From the practical point of view,it is of great significance to exploit a resource-rich,low-cost,durable and efficient bifunctional catalyst for the overall water decomposition on earth.Transition metals have made a significant contribution to the development of advanced electrocatalysts due to their high abundance,high activity and easy availability.In this paper,transition metal hydroxides,oxides,selenides and phosphides were constructed based on Co-based transition metal catalysts.The high electrical conductivity of the transition metal-based catalyst promotes the electron transfer of the catalyst,thus improving the catalytic activity.At the same time,the introduction of heteroatom can regulate the metal and improve the catalytic activity.The main research contents and results are as follows:（1）Firstly,a classic Co-based MOF material Co-ZIF-67 was prepared,and it was subjected to basic treatment to construct a Co-based hydroxide Co-ZIF-67-OH based on the MOF material.In order to verify the degree of hydroxylation,a series of characterization was carried out to prove that Co-ZIF-67 has been converted to hydroxyl cobalt oxide.The catalytic activity of Co-ZIF-67-OH for oxygen evolution was tested in a1 M KOH electrolyte.The current density of 10 m A cm^-2 was achieved at a low potential of 255 m V,which was better than that of IrO₂（355 m V）.At 30 m A cm^-2,the activity of Co-ZIF-67-OH did not decrease significantly after 30 hours of stability test,which proved that the prepared catalyst had good stability.In order to verify the general applicability of this Mo F-based hydroxide preparation,the Fe-based MOF（Fe-MIL-88（A））and Ni-based MOF（Ni-MOF-74）were treated by the same method,and the corresponding hydroxides Fe-MIL-88（A）-OH and Ni-MOF-74-OH were obtained.After structural characterization and electrochemical performance tests,the two hydroxides have similar structural characteristics and oxygen evolution performance as Co-ZIF-67-OH.（2）A Co-based oxide CoNiO/NF,which is self-grown on foam nickel,was prepared by hydrothermal method.CoNiOSe/NF and CoNiOP/NF are prepared by doping heteroatoms Se and P by thermal reduction.A series of characterization and electrochemical tests were performed on these three catalysts.The results showed that CoNiOP/NF has excellent hydrogen and oxygen evolution performance due to the synergistic effect of P atoms and metal Co.It is a good dual-functional catalyst.In the overall water splitting test,when the current density is greater than 320 m A cm^-2,the performance of CoNiOP/NF is better than that of the precious metal combination Pt/C‖IrO₂.