Nitrogen fixation under ambient temperature and pressure using a gas diffusion electrode

为活化稳定的N_2分子，提出了建立反应域的新概念。反应层由含催化剂的疏水部分和亲水部分混合而成，具有丰富的反应域，氮气、电解质和催化剂应紧密存在于反应层中。研究了气体扩散电极结构和催化剂的优化。在气体扩散电极上研究了不同金属催化剂对氮的还原作用，这些催化剂是通过将氯化物溶液扩散到金属上而制备的。在Pd-Ru合金催化剂的气体扩散电极上发现了氨的形成。在Pd (50%) +Ru（50%）的催化剂组成下，氨的生成量最大，此时氨的生成电流效率小于1%，且随着电解时间的延长而降低。XPS未检测到吸附在催化剂上的氮原子。在纯钯和纯钌催化剂上没有检测到氨的形成。x射线荧光分析未发现Pd和Ru负载减少。为了证实氨的生成，在气相中考察了钯钌催化剂的反应性。将Pd、Ru和Pd-Ru黑色催化剂包氢沉积在Pd块体金属上，置于纯氮气氛中，对催化剂进行了重量测定。Pd-Ru黑色催化剂的重量下降幅度大于Pd和Ru催化剂，说明在Pd-Ru黑色催化剂上可以生成氨。

New concept to make reaction domain for activating stable N_2 molecules was proposed as described below. Reaction layr having plenty of reaction domain, in which N_2 gas, electrolyte and catalysts should exist closely each other, consists of mixture of hydrophobic portion with catalysts and hydrophilic portion. The optimization of structure and catalysts at gas-diffusion electrodes was investigated in this work.Nitrogen reduction was examined at gas-diffusion electrodes with various metallic catalysts, which were prepared by spreading their chloride solutions and then the reduction of them to the metals. The formation of ammonia was found at gas-diffusion electrodes with Pd-Ru alloy catalysts. The amount of ammonia formed is maximum at catalyst composition of Pd (50%) +Ru (50%), at which the current efficiency for ammonia formation is less than 1% and decreases with electrolyte time. Nitrogen atoms adsorbed on the catalysts were not detected by XPS measurements. Ammonia formation was not detected at pure Pd and Ru catalysts. Decrease of Pd and Ru loaded was not found using by X-ray fluorescence analysis.The reactivity at Pd-Ru catalysts was examined in gas phase in order to confirm the ammonia formation. When Pd, Ru and Pd-Ru black catalysts deposited on Pd bulk metal with hydrogen occluded were kept in pure nitrogen atmosphere, the gravimetry of these catalysts was carried out. The weight of Pd-Ru black catalysts decreases more than of Pd and Ru catalysts, i.e.this result indicates that ammonia formation can take place at Pd-Ru black catalysts.