Study On Electrocatalysis Of Oxygen Reduction Reaction Based On Doped Hollow Carbon Nanospheres

With the deterioration of the global environment pollution, increasingly serious energy crisis, high rapid population growth and economic development, human beings are more dependent on clean and renewable sources. The fuel cell possesses the advantages of high conversion efficiency, environmental benignity, etc. Yet, the poor stability, CO and methanol poisoning, the high cost and the limited natural resource of Pt have blocked its large-scale application. In the recent years, doped carbon-based catalysts have attracted a great attention for oxygen reduction reaction (ORR). Hollow carbon spheres (HCSs) have been paid considerable attention to because of their superior properties such as low density, high specific surface area, good chemical stability and electrical conductivity. These features guarantee them promising in drug delivery, catalysis, energy conversion and storage. B-doped hollow carbon nanospheres (BHCSs), N-doped hollow carbon nanospheres (NHCSs) and B/N-doped hollow carbon nanospheres (BNCSs) have been synthesized and applied to ORR in fuel cell. The main points of this dissertation are described as follows:Via a simple and facile hydrothermal reaction, the BHCSs were obtained after carbonization by controlling the ratio of 4-hydroxyphenylboronic acid and resorcinol and calcination temperature. BHCSs were further characterized by many effective measurements, such as field emission scanning electron microscopy (FE-SEM), field emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET), Thermogravimetric (TG), dynamic light scattering analysis (DLS), confirming that the carbon nanospheres with uniform particle size and about 200 nm diameter basically retained the surface state after calcination.After electrode modified with the resulting BHCSs, Cyclic Voltammetray (CV) and linear sweep voltammetry (LSV) were used to investigate the catalytic activities of BHCSs to ORR in alkaline electrolyte. The experimental data showed that electrocatalytic reduction current was increasing with calcination temperature and the ratio of 4-hydroxyphenylboronic acid and resorcinol. When the ratio of 4-hydroxyphenylboronic acid and resorcinol is 3:7 as well as the calcination temperature arrived at 900℃, BHCSs show the best electrocatalytic catalysts to ORR.BNCSs have been composited by pyrolysis of BHCSs and urea at high temperatures. BNCSs were further characterized by many effective measurements, such as such as field emission scanning electron microscopy (FE-SEM), field emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET), Thermogravimetric (TG), confirming that the BNCSs retained well the spherical morphology with higher specific surface area.After electrode modified with the resulting BNCSs, Cyclic Voltammetray (CV) and linear sweep voltammetry (LSV) were used to investigate the catalytic activities of BNCSs to ORR in alkaline electrolyte. The experimental data demonstrated that calcination temperature and the ratio of BHCSs and urea influence the electrochemical activities of BNCSs. Compared with BHCSs and NHCSs, BNCSs own better electrochemical activities to ORR, which have a promising application in fuel cells.