Hard carbon is regarded as one of the most promising anode materials for sodium-ion battery. However, the ash content of the hard carbon anode inherited from the precursor have several negative impacts on the electrochemical performance of hard carbon. The traditional method utilizes strong inorganic acid washing to reduce the ash content of hard carbon. However, this method results in heavy environment pressure and safety hazards. Therefore, it’s necessary to exploring an alternative ash content removal method which is safer and environment friendly. This project develops an environmentally friendly approach to remove ash from hard carbon by using acetic acid. This approach effectively reduces the ash content and enhances the electrochemical performance of the hard carbon anode. The ash content of hard carbon decrease from 1.57 wt% to 0.655 wt% after the 4 mol /L acetic acid treatment. The two-step treatment process also studied in this project and shows a better ash removal ability than one-step treatment process. The ash content of 4 mol /L acetic acid and 20 wt% KOH only 0.28 wt%. Furthermore, the electrochemical performance of the two- step treated hard carbon exhibits notable improvements, including enhanced initial Columbic efficiency (from 84.53% to 88.11%), reversible capacity (from 244.2 mAh g-1 to 280.8 mAh g-1). The long cycle performance of chemical treated hard carbon anode need further investigations in future studies. / Hårt kol anses vara ett av de mest lovande anodmaterialen för natriumjonbatterier. Askhalten i den hårda kolanoden som ärvts från prekursorn har dock flera negativa effekter på den elektrokemiska prestandan hos hårt kol. Den traditionella metoden använder stark oorganisk syratvättning för att minska askhalten av hårt kol. Denna metod resulterar dock i hög miljöbelastning och säkerhetsrisker. Därför är det nödvändigt att utforska en alternativ metod för borttagning av askinnehåll som är säkrare och miljövänligare. Detta projekt utvecklar ett miljövänligt tillvägagångssätt för att ta bort aska från hårt kol genom att använda ättiksyra. Detta tillvägagångssätt reducerar effektivt askinnehållet och förbättrar den elektrokemiska prestandan hos den hårda kolanoden. Askhalten i hårt kol minskar från 1,57 viktprocent till 0,655 viktprocent efter 4 mol/L ättiksyrabehandlingen. Tvåstegsbehandlingsprocessen studerades också i detta projekt och visar en bättre förmåga att avlägsna aska än enstegsbehandling. Askhalten av 4 mol/L ättiksyra och 20 viktprocent KOH är endast 0,28 viktprocent. Dessutom uppvisar den elektrokemiska prestandan hos det tvåstegsbehandlade hårda kolet anmärkningsvärda förbättringar, inklusive förbättrad initial Columbic effektivitet (från 84,53 % till 88,11 %), reversibel kapacitet (från 244,2 mAh g-1 till 280,8 mAh g-1). Den långa cykelprestandan hos kemiskt behandlad hård kolanod behöver ytterligare undersökningar i framtida

Made available in DSpace on 2014-12-17T15:42:17Z (GMT). No. of bitstreams: 1 EdjaneFBS_TESE.pdf: 3916289 bytes, checksum: c86ba6653bacd96524384f5ddbd3741b (MD5) Previous issue date: 2012-08-03 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Nanostructured materials have been spreading successfully over past years due its size and unusual properties, resulting in an exponential growth of research activities devoted to nanoscience and nanotechnology, which has stimulated the search for different methods to control main properties of nanomaterials and make them suitable for applications with high added value. In the late 90 s an alternative and low cost method was proposed from alkaline hydrothermal synthesis of nanotubes. Based on this context, the objective of this work was to prepare different materials based on TiO2 anatase using hydrothermal synthesis method proposed by Kasuga and submit them to an acid wash treatment, in order to check the structural behavior of final samples. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), adsorption/desorption of N2, thermal analysis (TG/DTA) and various spectroscopic methods such as absorption spectroscopy in the infrared (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All the information of characterizations confirmed the complete conversion of anatase TiO2 in nanotubes titanates (TTNT). Observing the influence of acid washing treatment in titanates structure, it was concluded that the nanotubes are formed during heat treatment, the sample which was not subjected to this process also achieved a complete phase transformation, as showed in crystallography and morphology results, however the surface area of them practically doubled after the acid washing. By spectroscopy was performed a discussion about chemical composition of these titanates, obtaining relevant results. Finally, it was observed that the products obtained in this work are potential materials for various applications in adsorption, catalysis and photocatalysis, showing great promise in CO2 capture / Materiais nanoestruturados t?m se difundido com sucesso ao longo dos ?ltimos anos, isso devido ao seu tamanho e propriedades incomuns, resultando em um crescimento exponencial das atividades de investiga??o dedicadas ? nanoci?ncia e nanotecnologia, o que tem estimulado a procura por diferentes m?todos que possam controlar as principais propriedades dos nanomateriais a fim de adequ?-los para aplica??es de alto valor agregado. No final da d?cada de 90 um m?todo alternativo e de baixo custo foi proposto a partir da s?ntese hidrot?rmica alcalina de nanotubos. Baseando-se nesse contexto, o objetivo deste trabalho foi preparar diferentes materiais ? base de TiO2 anatase utilizando o m?todo de s?ntese hidrot?rmica proposto por Kasuga e submet?-los em seguida a um tratamento de lavagem ?cida, com o prop?sito de verificar o comportamento estrutural das amostras finais. Essas foram caracterizadas por difratometria de raios X (DRX), microscopia eletr?nica de varredura (MEV), microscopia eletr?nica de transmiss?o (MET), adsor??o/dessor??o de N2, an?lise t?rmica (ATG/ATD) e diferentes m?todos espectrosc?picos como, espectroscopia de absor??o na regi?o do infravermelho (FT-IR), espectroscopia Raman e espectroscopia fotoeletr?nica de raios X (XPS). O conjunto de caracteriza??es se complementou, confirmando a transforma??o completa do TiO2 anatase de partida em titanatos nanotubulares (TTNT). Ao observar a influ?ncia que o tratamento de lavagem ?cida exerce na estrutura do mesmo, conclui-se que os nanotubos s?o formados durante o tratamento t?rmico, pois a amostra que n?o foi submetida ao processo tamb?m alcan?ou uma transforma??o completa de fase, conforme os resultados de cristalografia e morfologia, entretanto a ?rea espec?fica deles ? praticamente dobrada ap?s a lavagem ?cida. Por espectroscopia foi realizada uma minusiosa discuss?o acerca da composi??o qu?mica desses titanatos, obtendo resultados relevantes. Por fim, ressalta-se que os produtos obtidos nesse trabalho s?o materiais com potencial para diferentes aplica??es em adsor??o, cat?lise e fotocat?lise, se mostrando promissores na captura do CO2