Microwave Absorption And Electrocatalytic Oxygen Evolution Performance Of MOF Derived Carbon Matrix Composites

In recent years,metal-organic frameworks?MOFs?have been widely used as anattractive porous material due to their structural diversity,designability,and ultra-high specific surface area.The carbon-based composite materials derived from MOFs have great potential application in the fields of electromagnetic wave absorption,energy storage and conversion due to their excellent magnetic and electrochemical properties.In this paper,the imidazole ester metal organic framework material?ZIF-based?was selected as the precursor.Two different carbon-based composite materials were prepared by different element?S,P and Fe?control,and the test of electromagnetic wave absorption and electrocatalytic oxygen evolution were carried out.1.ZIF-67 was selected as the precursor,and subsequently we obtained the rhombohedral dodecahedral Co/C composite under high temperature pyrolysis based on the idea of derivatization preparation.In the later stage,three different composites of CoP/C,CoS₂/C and CoS_2-xP_x/C were obtained by introducing phosphorus and sulfur source using low-temperature annealing method.The results of SEM and TEM analysis show that the shape of the composite can still maintain its original regular shape under high temperature treatment,and the whole is composed of amorphous carbon matrix modified by uniformly dispersed nanoparticles.The electromagnetic parameters of the composite material were calculated and sulfur phosphating sample(CoS_2-xP_x/C)show the best electromagnetic wave absorption performance of-68 dB minimum reflection at the matching thickness of 1.5 mm,and the absorbing width of the reflection loss value<-10dB reaches 4.6 GHz.Simultaneously,the above samples were tested for electrocatalytic oxygen evolution reaction?OER?performance.The results showed that the CoS_2-xP_x/C sample exhibited the best OER performance in 1M KOH aqueous solution,and only required an overpotential of 390 mV to reach 10 mA/cm².The corresponding Tafel slope is 92 mV/dec.2.ZIF-8/ZIF-67 was selected as the precursor,and the Fe source was introduced by water-oil impregnation method,and CoFe_x@Co@C composite material was obtained by high temperature pyrolysis.CoFe_0.19@Co@C,CoFe_0.26@Co@C and CoFe_0.47@Co@C were prepared by adjusting the amount of iron incorporation.The results of SEM and TEM analysis show that the composites obtained by high temperature treatment exhibit irregular multi-dimensional structure,and the whole consists of amorphous carbon matrix modified by dispersed nanoparticles.The electromagnetic parameters of the composite materials were calculated to show the CoFe_0.26@Co@C exhibited the best electromagnetic wave absorption performance,with a minimum reflection loss value of-62.5 dB at the matching thickness of 1.5mm.The absorbing width of the reflection loss value<-10 dB reaches 4.8 GHz.Simultaneously,the above samples were tested for electrocatalytic oxygen evolution performance.The results indicated that the CoFe_0.47@Co@C sample showed the best OER performance in 1M KOH aqueous solution,and only required overpotential of 340 mV to reach 10 mA/cm²,corresponding to the Tafel slope of 47 mV/dec.