Controllable Synthesis And Electrocatalytic Performance Of Manganese Phosphate

Zinc-air batteries have the advantages of high specific energy,abundant resources,good safety,and no pollution to green.They are one of the most promising energy sources in the future.Among them,the electrocatalyst of the air electrode is a key factor that restricts its development.It requires the electrocatalyst to have a dual-function catalyst with high-efficiency oxygen reduction reaction and oxygen evolution reaction catalytic activity.In this paper,different structures of manganese phosphate electrocatalysts have been synthesized by adjusting the ratio of different materials using hydrothermal reaction.The prepared electrocatalysts were characterized by XRD,TEM,SEM,Raman and XPS.The effects of different Mn:P ratios on the catalyst structure and morphology were investigated.With the increase of the ratio of Mn:P,the diffraction peaks in the X-ray diffraction pattern become more obvious,ie,the degree of crystallinity increases,and the uniformity of its morphology also increases.Compared to the prepared MnPO_（3:2）catalyst,the MnPO_（1:1）catalyst prepared with a Mn:P ratio of 1:1 has a relatively thin platelet structure and is more prone to distribution of active sites in the catalyst.The reaction occurred;the catalytic performance of manganese phosphate was tested in the basic conditions of the three-electrode system,the prepared MnPO_（1:1）catalyst showed excellent ORR and OER performance,its transfer electron number,cyclic voltammogram ratio and Tafel slopes explain their excellent catalytic properties,respectively.The manganese phosphate electrocatalyst was applied to the zinc-air battery.The prepared MnPO_（1:1）catalyst had excellent charge and discharge performance and cycle stability.After 100 cycles of charge-discharge cycles,the commercial Pt/C discharge voltage decreased significantly.While the prepared MnPO_（1:1）catalyst had almost no decay after 100 cycles.In addition,the effect of different loadings on the charge and discharge of the catalyst was tested.The results show that as the loading of the catalyst increases,the voltage difference between charge and discharge decreases,ie,the performance of the battery increases with the increase of the catalyst.At the same time,72-C with good conductivity was loaded on manganese phosphate with good ORR performance.The effects of solvent and calcining on the structure and morphology of the samples were studied.The 72-C/MnPH₀（EG）catalyst prepared with ethylene glycol/water mixed solvent had a relatively pure phase structure,and the composed sheet-like structure was also relatively thin.The Raman results show a low degree of disorder,these structures help to enhance the catalytic activity of the catalyst.The electrocatalytic performance of 72-C-loaded manganese phosphate was tested.72-C/MnPH₀（EG）catalyst showed good ORR and OER catalytic performance.Both the CV area ratio and the Tafel slope also show that it has good catalytic performance;the results of the zinc-air battery test show that the72-C/MnPH₀（EG）catalyst has good charge and discharge performance,and the charge and discharge platform is almost 100 cycles after cycling.It does not change and shows good cycle stability of the catalyst.