Preparation And Performance Of Mesoporous Binary Metal Oxide Nanorods As Oxygen Evolution Catalyst

Hydrogen,as a clean and pollution-free,high calorific value,renewable and other advantages energy source,is widely concerned by people,which is expected to become an important source of energy in the future.In the application of hydrogen energy,hydrogen storage is the premise and hydrogen production is the key.Hydrogen production from water electrolysis with its simple process,high purity products,no environmental pollution and other characteristics has become the most promising mean of hydrogen production.But its high energy consumption limits its large-scale applications.At present,the energy consumption of hydrogen production by water electrolysis is mainly concentrated in the anodic oxygen evolution reaction（OER）.So seeking a cheap and easy to get,high performance and strong stability anodic oxygen evolution catalyst has become the main challenges of hydrogen applications.Ni-based,Co-based and other transition metal oxides with their low cost and high oxygen evolution performance have become the main research hotspot of current oxygen evolution catalyst.But there are still some problems that poor stability and catalytic activity is lower than the precious metal oxide catalysts.The results show that the oxygen evolution performance of the transition metal oxide catalysts can be further improved by chemical modification and structural modification.Based on this,a series of Ni_1-xFe_xO_y,Co1-xFex Oy materials were prepared by elemental doping and nano-regulation in this paper.The excellent oxygen evolution catalyst was obtained and the relationship between the structure,composition and catalytic performance was discussed.The specific contents are as follows:（1）One-dimensional Ni_1-xFe_xO_y（0≤x≤1）porous nanorods with different Fe-dopingamounts were prepared by the thermal decomposition of Ni-Fe-based coordination polymer precursors at 350 °C under air atmosphere.The results show that the grain size of the catalyst decreases at first and the composition of the material changes with the increase on the Fe-doping amount.The shift in the dopant concentration of Fe was further reflected in the structural transformation from a Ni O（<33 at% Fe）rock-salt structure to a biphasic NiO/NiFe₂O₄（33 at%Fe）heterostructure,a NiFe₂O₄（66 at% Fe）spinel structure,and eventually toα-Fe2O3（100 at% Fe）.The electrochemical test results show that the oxygen evolution performance increases first and then decreases with the increase of Fe-doping amount.The performance of NiO/NiFe₂O₄（33 at% Fe）heterostructure is the best,the overpotential is 302 mV and the Tafel slope is 42mV/dec.According to the results of structure and performance,the relationship between structure and activity is studied deeply.（2）The catalyst is obtained from the pyrolysis 33 at% Fe catalyst precursor at300 °C,400 °C and 450 °C respectively compared to that at 350 °C.The structural characterization shows that the precursor is not completely restored at300 °C and α-Fe2O3 appears in the catalyst at 450 °C.The electrochemical test results show that the performance of NiO/NiFe₂O₄ heterostructure obtained at350 °C is the best.（3）The catalyst is obtained from the pyrolysis 66 at% Fe catalyst precursor at300 °C,400 °C and 450 °C respectively compared to that at 350 °C.The results show that the spinel oxide NiFe₂O₄ obtained at 350 °C has the best performance,the overpotential is 342 mV and the Tafel slope is 44 mV/dec.（4）One-dimensional Co1-x FexOy（0≤x≤1）porous nanorods with different Fe-doping amounts were prepared by the same method.It was found that with the increase of Fe-doping amount,the grain size（except 100 at% Fe）gradually decreased,while the specific surface area gradually increased.The electrochemical test shows that the performance of 16 at% Fe catalyst is the best,indicating that the Fe-doping amount is the main factor affecting the performance of the catalyst.