Preparation And Electrochemical Properties Of Biomass-based Carbon Materials

The precious metal platinum-based catalysts have been widely used in the fuel cells,but the practical application of the catalysts has been largely hindered by its high cost.Herein,we report a simple and green preparation method to prepare a series of heteroatoms doped carbon-based oxygen reduction catalysts by using the cheap biomass as precursor pyrolysis.The successful fabrication of heteroatoms doped carbon-based oxygen reduction catalysts are confirmed by scanning electron microscope（SEM）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,Raman spectroscopy（Raman）,specific surface area analyzer（BET）and investigation of the electrocatalytic performance of the prepared materials by electrochemical testing.（1）Different kinds of nitrogen-doped carbon materials have been prepared by using Typha,zinc chloride as precursor and salt sealant,respectively.The materials were characterized by SEM,XRD,XPS and BET.Experimental results show that the nitrogen doping amount can be significantly enhanced by salt-sealing method,especially for the content of pyridine nitrogen.The prepared nitrogen-doped carbon materials with high specific surface area(967.18 m² g^-1),high nitrogen doping content（4.92 at%）and high pyridine nitrogen content（45.82%）when the salt-sealing mass ratio(m_ZnCl2:m_TOP)is 8.The obtained materials not only exhibit high electrocatalytic activity for the oxygen reduction reaction（ORR）,but also exhibit good stability and methanol resistance in alkaline（0.1 M KOH）,in acidic（0.1 M HClO₄）and in neutral（0.05 M PBS）solutions,when the mass ratio of zinc chloride to Typha(m_ZnCl2:m_TOP)is 8.（2）By using the Kiwifruit peel and zinc chloride as precursor and salt sealant,the nitrogen-doped porous carbon materials have been successfully prepared by one-step method.The obtained materials were characterized by SEM,XRD,XPS and BET.The results show that the nitrogen fixation by zinc chloride salt is universal.The prepared nitrogen-doped carbon materials with specific surface area up to 1484.40 m² g^-1,the nitrogen content can reach 4.21 at%and the pyridine nitrogen content is 32%when the mass ratio of zinc chloride to fruit peel is 7(m_ZnCl2:m _MHT).The catalytic activity for the ORR of the prepared catalysts was investigated by RDE and RRDE.The results showed that the as-prepared MC7 has an onset potential of 0.968V vs.RHE,and half-wave potential E_1/2≈0.836 V during ORR in 0.1 M KOH solution,which was close to commercial 20 wt%Pt/C catalyst.the resulting MC7 also shows more excellent electrochemical cycle stability and methanol resistance than commercial Pt/C for ORR in alkaline media,which provides a new way to substitute for commercial Pt/C catalyst.At the same time,the material has great application valued in electrochemical sensor.（3）In this thesis,heteroatoms co-doped porous carbons were prepared by chemical activation of Kiwifruit peel with KOH.from fruit peel of Kiwifruit by chemical activation processes with KOH.The structure of prepared carbon materials were examined by SEM,XPS,XRD,Raman and BET.The results showed that nitrogen,oxygen,and sulfur in situ co-doped carbon can be prepared by the pre-carbonization and activation processes.An activated carbon significantly increases the high surface area up to 1698.6 m² g^-1 by KOH activation.The supercapacitor performance of the prepared carbon material was evaluated in a three-electrode system.When the mass ratio of the KOH and the kiwi peel is about 3:1,the high specific capacitance of 221.1 F g^-1 is obtained at a scan rate of 5 mV s^-1.Furthermore,the electrode material has good rate performance and excellent cycling performance.the as-prepared catalyst MHTC-3 exhibited good electrocatalyst performance(E_onset≈0.952 V,E_1/2≈0.756 V)for the oxygen reduction reaction in 0.1 M KOH solutions.