Energy storage systems are becoming continuously more important in the present due to their growing usage in electro-electronic devices, electric cars and other technologies. In this context, supercapacitors are been studied in view of their intermediate properties in regards to the conventional energy storage systems, such as batteries and capacitors. Different materials like oxides, carbonaceous materials among others are being investigated. Hydrated and amorphous ruthenium dioxide is the most evaluated oxide due to its high theoretical and experimental specific capacitance. However, this oxide has disadvantages such as high cost and toxicity (non-environmentally friendly). Among the materials investigated to replace the ruthenium dioxide, manganese dioxide is a promising candidate, because of its high theoretical specific capacitance, low cost and also it is environmentally friendly. However, in relation to the values of electric conductivity and specific surface area, the manganese dioxide does not have comparable values such as those of ruthenium dioxide, being these two properties the most investigated. One of the ways to improve the conductivity of manganese dioxide is to mix it with carbonaceous materials, such as acetylene black. The resulting mixture has also a better charge collection due to the interaction between both species. Despite this, the acetylene black cannot contribute to increase the specific surface area, and causes the amount of electroactive material to be lower in the supercapacitor electrode. So, this project intends to prepare composite materials by mixing nanometric manganese dioxide, polyaniline activated carbon (PAC) and a binder agent (PVDF) in distinct mass proportions and evaluate their respective electrochemical performance as supercapacitor electrode materials. The project will include the synthesis of nanometric manganese, dioxide (MnO2), synthesis of polyaniline activated carbon (PAC), preparation of the composite electrodes and electrochemical characterizations. The MnO2 synthesis will be done using the microwave assisted hydrothermal methodology, with KMnO4 and acetone being the reactants. The PAC will be synthesized by carbonizing polyaniline doped with p-toluenesulfonate in a tubular furnace under N2 atmosphere and activated with KOH, followed by another heating under N2 atmosphere. The resulting material will be washed with a HCl solution. The composite materials will be prepared by mixing MnO2, PAC and PVDF in various proportions with cyclopentanone, leading to the formation of a slurry that will be applied on the platinum electrodes. These electrodes will be tested electrochemically by cyclic voltammetry and charge/discharge at constant current. For these tests, a conventional electrochemical cell will be used containing a previously prepared working electrode, a platinum blade as a counter electrode and a saturated calomel electrode as a reference electrode, immersed in a 0,1 mol L-1 Na2SO4 solution.
News published in Agência FAPESP Newsletter about the scholarship:
Mifumo ya kuhifadhi nishati inakuwa muhimu zaidi katika siku hizi kwa sababu ya matumizi yao yanayoongezeka katika vifaa vya umeme, magari ya umeme na teknolojia nyingine. Katika muktadha huu, supercapacitors ni alisoma kwa kuzingatia mali yao kati katika suala la mifumo ya kawaida ya kuhifadhi nishati, kama vile betri na capacitors. Vifaa tofauti kama vile oksidi, vifaa vya kaboni miongoni mwa wengine vinachunguzwa. Hydrated na amorphous ruthenium dioksidi ni oksidi zaidi tathmini kutokana na uwezo wake wa juu wa kinadharia na majaribio maalum. Hata hivyo, oksidi hii ina hasara kama vile gharama ya juu na sumu (si mazingira ya kirafiki). Kati ya vifaa vya kuchunguzwa kuchukua nafasi ya ruthenium dioksidi, manganese dioksidi ni mgombea wa matumaini, kwa sababu ya uwezo wake wa juu wa kinadharia, gharama ya chini na pia ni kirafiki na mazingira. Hata hivyo, kwa uhusiano na maadili ya conductivity umeme na eneo maalum uso, manganese dioksidi haina maadili kulinganisha kama wale wa ruthenium dioksidi, kuwa mali hizi mbili zaidi kuchunguzwa. Njia moja ya kuboresha conductivity ya manganese dioksidi ni kuchanganya na vifaa carbonaceous, kama vile acetylene nyeusi. Mchanganyiko unaotokana pia una mkusanyiko bora wa malipo kwa sababu ya mwingiliano kati ya spishi zote mbili. Hata hivyo, acetylene nyeusi haiwezi kuchangia kuongeza eneo maalum uso, na husababisha kiasi cha electroactive nyenzo kuwa chini katika supercapacitor electrode. Kwa hivyo, mradi huu unakusudia kuandaa vifaa vya mchanganyiko kwa kuchanganya nanometric manganese dioxide, polyaniline activated carbon (PAC) na kitanzi cha kuunganisha (PVDF) katika uwiano tofauti wa wingi na kutathmini utendaji wao wa umeme kama vifaa vya supercapacitor. Mfano wa nanocrystalline ni pamoja na synthesis ya nanocrystalline manganese, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline, polyaniline. MnO2 synthesis ni mchakato wa hydrothermal na microwave-assisted, ambayo hutumiwa na kemikali za kemikali za kemikali za kemikali za kemikali za kemikali. PAC itakuwa synthesized na carbonizing polyaniline doped na p-toluenesulfonate katika tanuru tubular chini ya N2 anga na kuanzishwa na KOH, ikifuatiwa na joto nyingine chini ya N2 anga. Vifaa vilivyotokana vitaoshwa kwa suluhisho la HCl. Kwa mfano, nyenzo za mchanganyiko zitatayarishwa kwa kuchanganya MnO2, PVA na PVDF katika uwiano tofauti na cyclopentane, na kuongoza kwa malezi ya slurry ambayo itatumika kwenye elektroni za platinamu. Electrodes hizi itakuwa majaribio electrochemically na cyclic voltammetry na malipo / discharge katika sasa mara kwa mara. Kwa ajili ya vipimo hivi, kawaida electrochemical kiini itakuwa kutumika, ikiwa ni pamoja na electrode kazi tayari tayari, platinum blade kama counterelectrode na saturated calomel electrode kama electrode rejea, kuzamishwa katika 0,1 mol L1 Na2SO4 ufumbuzi. Habari zilizochapishwa katika Agência FAPESP Newsletter kuhusu udhamini: