Effect Of AC Magnetic Field On Electrolysis OER Performance Of Different Magnetic MOFs Derivatives

Hydrogen（H₂）is considered as an ideal energy source to alleviate energy crisis and environmental problems due to its high energy density,zero carbon emission and renewable characteristics.The technology of electrolysis of aquatic hydrogen using renewable energy such as wind and solar energy has great development prospect.However,the kinetics of anodic oxygen evolution（OER）reaction is slow,which seriously affects the electrolysis efficiency of water.Therefore,the development of non-noble metal based OER catalyst with excellent performance is the key to large-scale industrial hydrogen production.In addition,the magnetic field of water electrolysis significantly enhances the effect of the application of excellent potential in this field.In this paper,the effects of MOFs composition and AC magnetic field intensity on the composition,microstructure and electrocatalytic performance of derivatives are studied,and the mechanism of AC magnetic field on OER activity of different magnetic MOFs derivatives is discussed.The main research results are as follows:（1）Two kinds of MOFs are successfully loaded on CP（carbon paper）surface by solvothermal method,and paramagnetic nitrogen-doped carbon material loaded on CP is obtained after heat treatment.The specific surface area,average pore size and volume of ZIF-8 derivatives are 1559 m²·g^-1,0.57 nm and 1.59 cm³·g^-1,respectively.The OER overpotential and Tafel slope of ZIF-8 derivatives are 334mV@10 mA·cm^-2 and 187 mV Dec^-1,respectively.The OER overpotential of ZIF-8derivatives first decreased with the increase of magnetic field inte nsity and then remains unchanged.When the magnetic field intensity is 5.54 mT,the overpotential of ZIF-8 derivatives is the smallest,which is 316 mV,which is 20.4%lower than that before the introduction of magnetic field.This is mainly because the magnetohydrodynamics effect derived fromAC magnetic field enhances the mass transfer effect of electrocatalytic process.（2）Three kinds of MOFs of（Co/Ni）₁Fe₂-BTC（benzenetricarboxylic acid）are successfully loaded on CP surface,and three kinds of ferro magnetic transition metal oxides are obtained after heat treatment.The specific surface area of NiFe ₂O₄is 174.94 m²·g^-1,the average pore size is 0.48 nm,the saturation magnetization（M _s）is 135.91 emu·g^-1,and the coercivity（H_c）is 315.30 Oe.The OER overpotential and Tafel slope of CP NiFe₂O₄ are 265 mV@10 mA·cm^-2 and 76 mV·Dec^-1,respectively.When the external magnetic field intensity is 6.01 mT,the minimum overpotential of CP NiFe₂O₄ is 126 mV,which is 63.3%lower than that.The analysis shows that MR effect（magnetoresistance effect）plays a leading role in the process of magnetic field-assisted MOFs derived oxide OER.（3）Sulfur-doped（Co/Ni）₁Fe₂-BTC supported by CP is obtained,in which S-Ni-Fe₂O₃ has a specific surface area of 126.80 m²·g^-1 and an average pore size of0.73 nm,and has the best magnetic and thermal properties.OER performance test shows that the over-potential and Tafel slope of S-Ni-Fe₂O₃ are 224 mV@10mA·cm^-2（with iR correction）and 88 mV·Dec^-1,respectively.When the external magnetic field intensity is 5.54 mT,the minimum cross potential of S-Ni-Fe₂O₃ is161 mV（without iR correction）,which is 46.9%lower than that,mainly due to the magneto-thermal effect.