CAJ | 학술논문

以Vulcan XC-72炭黑为载体,通过对炭载体石墨化处理和表面化学修饰,将其与化学沉淀法制备的纳米级LaMnO3颗粒共混,再经特定温度下煅烧,制备出改性炭黑-LaMnO3复合材料. X射线光电子能谱和热重分析表明,当煅烧温度在300°C时,炭载体与LaMnO3纳米颗粒之间形成了大量C-O-M (M = La, Mn)化学键.扫描电子显微镜和高分辨透射电子显微镜分析发现,纯相LaMnO3纳米颗粒主要呈现短棒、三支棒或竹节棒的形貌特征,炭载体则为具有完整石墨层的空心球结构, LaMnO3均匀分散在炭载体上.在25°C,1 mol/L NaOH溶液中的电化学测试结果表明,成分比(LaMnO3：C)为2：3的复合材料具有很高的氧还原电催化活性,氧还原反应电子数为3.81,中间产物H2O2产率为9.5%,其活性接近商业Pt/C催化剂(E-TEK).高的氧还原电催化活性主要归因于LaMnO3纳米颗粒与炭载体之间形成了大量共价键.
이Vulcan XC-72탄흑위재체,통과대탄재체석묵화처리화표면화학수식,장기여화학침정법제비적납미급LaMnO3과립공혼,재경특정온도하단소,제비출개성탄흑-LaMnO3복합재료. X사선광전자능보화열중분석표명,당단소온도재300°C시,탄재체여LaMnO3납미과립지간형성료대량C-O-M (M = La, Mn)화학건.소묘전자현미경화고분변투사전자현미경분석발현,순상LaMnO3납미과립주요정현단봉、삼지봉혹죽절봉적형모특정,탄재체칙위구유완정석묵층적공심구결구, LaMnO3균균분산재탄재체상.재25°C,1 mol/L NaOH용액중적전화학측시결과표명,성분비(LaMnO3：C)위2：3적복합재료구유흔고적양환원전최화활성,양환원반응전자수위3.81,중간산물H2O2산솔위9.5%,기활성접근상업Pt/C최화제(E-TEK).고적양환원전최화활성주요귀인우LaMnO3납미과립여탄재체지간형성료대량공개건.
Covalent coupling between LaMnO3 nanoparticles and carbon black to produce a composite catalyst for oxygen reduction reaction (ORR) was achieved by physical mixing of modified carbon and per-ovskite-type LaMnO3 nanoparticles, followed by sintering at different temperatures. Perovskite-type LaMnO3 nanoparticles were first synthesized via chemical precipitation, and the carbon sup-port (Vulcan XC-72) was modified using graphitization, followed by HNO3 and ammonia treatments. The morphology and electronic states of the carbon black-LaMnO3 hybrid catalyst were character-ized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The loaded LaMnO3 particles featured rod-like, three bars-like, and bamboo rod-like structures and were homogeneously dispersed in the carbon matrix that featured a hollow spherical structure. At a sintering temperature of about 300 °C, C-O-M (M = La, Mn) bonds formed at the interface between the carbon and LaMnO3 nanoparticles. Electrochemical measurements in 1 mol/L NaOH showed that the carbon-LaMnO3 hybrid prepared at a LaMnO3/GCB mass ratio of 2:3 displayed the highest electrocatalytic activity towards ORR among all the synthesized hybrid catalysts. The electrocata-lytic activity was comparable with that obtained by commercial Pt/C catalyst (E-TEK). The average electron transfer number of ORR was ~3.81, and the corresponding yield of the hydrogen peroxide intermediate was ~9.5%. The remarkably improved electrocatalytic activity towards ORR was likely because of the formation of covalent bonds (C-O-M) between the LaMnO3 nanoparticles and carbon that can effectively enhance the ORR kinetics. This information is important to understand the physical origin of the electrocatalytic activity of carbon-supported rare earth oxides as catalysts for ORR.