Herein, we demonstrate that the performance of mesoporous silica SBA-15 and SBA-15-Ag during plasma ammonia synthesis depends on the plasma conditions. At high power, the mesoporous silica SBA-15 without Ag produces the largest amount of ammonia, but the addition of Ag provides a minor benefit at lower powers. Plasma conditions were analyzed through optical emission spectroscopy using N₂, N₂⁺, and NH molecular bands and H_α line. Stark broadening of H_α line was used to find electron density, and N₂ molecular bands were used to assess N₂ vibrational excitation, important for plasma nitrogen decomposition. At similar input conditions, reactors with SBA-15 have higher electron density and higher N₂ vibrational temperature. Consistent with higher electron density, SBA-15 reactors have stronger N₂⁺ emission intensity relative to the neutral N₂. The addition of Ag results in higher N₂ rotational temperature, possibly due to localized heating. From the materials point of view, SBA-15 is a more robust catalyst with good surface area retention after plasma exposure due to the lack of local heating generated when a metal is in the structure. We identify two possible regimes during ammonia synthesis, a metal and a surface-plasma driven. At lower plasma densities, the addition of metal is beneficial, while at higher power and plasma density, the best performance is achieved without the aid of a metal catalyst.

Graphical Abstract

Mesoporous materials for Plasma Catalytic Ammonia Synthesis, at certain plasma conditions lead to different regimes, a plasma/surface and a metal dominated regimes of ammonia production.

中文翻译：

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识别等离子催化氨合成过程中的机制

在此，我们证明了介孔二氧化硅 SBA-15 和 SBA-15-Ag 在等离子体氨合成过程中的性能取决于等离子体条件。在高功率下，不含 Ag 的介孔二氧化硅 SBA-15 产生最大量的氨，但在较低功率下添加 Ag 提供的好处很小。_{通过使用N 2}、N ₂ ⁺和NH分子带和H _α线的发射光谱分析等离子体条件。_{用 H α}谱线的 Stark 展宽来求电子密度，用 N ₂分子谱带来评估 N ₂振动激发，对等离子体氮分解很重要。在类似的输入条件下，具有 SBA-15 的反应器具有更高的电子密度和更高的 N ₂振动温度。与更高的电子密度一致，SBA-15 反应器相对于中性 N _{2具有更强的 N 2} ⁺发射强度。Ag的添加导致更高的N ₂旋转温度，可能是由于局部加热。从材料的角度来看，SBA-15 是一种更坚固的催化剂，由于在结构中没有金属时产生的局部加热，因此在等离子体暴露后具有良好的表面积保持性。我们在氨合成过程中确定了两种可能的状态，一种是金属，另一种是表面等离子体驱动。在较低的等离子体密度下，添加金属是有益的，而在较高的功率和等离子体密度下，无需金属催化剂的帮助即可实现最佳性能。

图形概要

用于等离子催化氨合成的介孔材料在某些等离子条件下会导致不同的制氨方式、等离子/表面和以金属为主的制氨方式。