Influence of carbonaceous species on aqueous photo-catalytic nitrogen fixation by titania
Influence of carbonaceous species on aqueous photo-catalytic nitrogen fixation by titania
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DOI：
10.1039/c8fd00191j
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发表时间：
2019-07-01
影响因子：
3.4
通讯作者：
Hatzell, Marta C.
中科院分区：
文献类型：
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作者：
Liu, Yu-Hsuan;Vu, Manh Hiep;Hatzell, Marta C.
几十年来，有报道表明，在水性环境中通过二氧化钛进行光催化固氮是可能的。然而，对于反应如何进行，还没有达成共识。此外，质子化溶剂水溶液的存在以及氮和质子还原的氧化还原电位之间的相似性表明氨的产生是不可能的。在这里，我们重新调查光催化固氮二氧化钛在水环境中通过一系列的光催化和电催化实验。光催化测试表明，矿物相和金属掺杂剂在促进氮的光固定中起着边缘作用，当主要相是金红石和铁掺杂剂时，氨产量增加。然而，痕量的吸附的含碳物质的存在下，增加了氨的生产率的两倍，没有吸附的碳基物种的观察。这表明，碳物种在介导固氮过程中发挥了潜在的更大的作用，超过矿物相和金属掺杂剂。我们还展示了一种实验方法，旨在检测低水平的氨生产的光催化剂使用旋转环盘电极实验进行照明和不照明。与XRD一致，氨仅在具有金红石相二氧化钛的环处可辨别，而不是在具有混合相二氧化钛的环处可辨别。旋转环盘电极实验也可以提供一种新的途径，以达到更高的精度在检测低水平的氨。
For decades, reports have suggested that photo-catalytic nitrogen fixation by titania in an aqueous environment is possible. Yet a consensus does not exist regarding how the reaction proceeds. Furthermore, the presence of an aqueous protonated solvent and the similarity between the redox potential for nitrogen and proton reduction suggest that ammonia production is unlikely. Here, we re-investigate photo-catalytic nitrogen fixation by titania in an aqueous environment through a series of photo-catalytic and electrocatalytic experiments. Photo-catalytic testing reveals that mineral phase and metal dopants play a marginal role in promoting nitrogen photofixation, with ammonia production increasing when the majority phase is rutile and with iron dopants. However, the presence of a trace amount of adsorbed carbonaceous species increased the rate of ammonia production by two times that observed without adsorbed carbon based species. This suggests that carbon species play a potential larger role in mediating the nitrogen fixation process over mineral phase and metal dopants. We also demonstrate an experimental approach aimed to detect low-level ammonia production from photo-catalysts using rotating ring disk electrode experiments conducted with and without illumination. Consistent with the photocatalysis, ammonia is only discernible at the ring with rutile phase titania, but not with mixed-phase titania. Rotating ring disk electrode experiments may also provide a new avenue to attain a higher degree of precision in detecting ammonia at low levels.