Anodization Preparation of Ta3N5 Thin Films as Photoelectrodes for Water Splitting

• Main Authors: Chih-YungChang, 張智詠
• Other Authors: Hsi-Sheng Teng
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/76072095263052302208

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 101 === In the present work, a n-type semiconductor tantalum nitride(Ta3N5) film is fabricated by anodization. Ta3N5 with a band gap of 2.0 eV, which can absorb visible light and is suitable to be a good photoanode. From XRD and SEM analysis, which can know that Ta3N5 belong to orthorhombic phase, has the porous structure and the particle size of about 20~50 nm. In addition, immersing the Ta3N5 film in Co(NO3)2 solution then take it to nitride, can form a p-type cobalt nitride(Co5.47N) on it. By using Mott-Schottky, UV-Vis absorption and CV to check their conduction band, valance band and fermi level. With the p-n interface on Co5.47N-Ta3N5 film, it can greatly enhance the performance for photoelectrochemical water oxidation. Under AM 1.5 G simulated sunlight illumination, the photocurrent density of Co5.47N-Ta3N5 can reach 2.5mA/cm2, which is more larger than 30μA /cm2 of bare Ta3N5 film at 0.5V vs. Ag/AgCl in 0.5M KOH solution . From EIS and IMPS analysis, it is established that the intimate contact between Co5.47N and Ta3N5 can improve the electron-hole separation, decrease the recombination and reduce the resistance to the transport of electrons. By combining the photoelectrode system with GC, it can calculate the theoretical electron moles from current-time curve and detect the real gas evolution from GC at the same time, under 300W Xe lamp visible light illumination, at fixed potential. Through this system, which can prove that the water splitting gas evolution is form the photocurrent response.