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首页> 外文期刊>RSC Advances >Photocatalytic NOx abatement: why the selectivity matters
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Photocatalytic NOx abatement: why the selectivity matters

机译：光催化NOx减排：为什么选择性很重要

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Titanium dioxide photocatalysis offers an excellent way to oxidise NOx to nitrate and thus reduce air pollution. However, unmodified titanium dioxide also releases a significant amount of the toxic intermediate nitrogen dioxide in the process, a problem that is rarely discussed in previous literature. Herein, we highlight this issue by presenting systematic data on the activity and selectivity of a number of commercial titania powders. The photocatalytic performance of a previously developed W/N-codoped titanium dioxide is also reported which, for the first time, offers a way to eliminate this problem as it exhibits an exceptionally high selectivity towards nitrate. The selectivity appears to be solely dependent on the tungsten content, a concentration of 4.8 at.% is sufficient to induce a very high selectivity. Furthermore, the high selectivity could also be replicated by a W/N-codoped sample derived from the industrial sulphate synthetic process. The increased selectivity comes at the expense of absolute activity, which is lower than in the reference titania samples. This raises the question of how to properly evaluate NOx abatement photocatalysts when there are two factors to consider, activity and selectivity. To resolve this, we propose to define a new figure of merit for the evaluation of NOx abatement photocatalysts by distilling total NOx removal and selectivity into one value, the DeNOx index. It is derived by assigning a toxicity value to both NO and NO2 and then expressing the change in total toxicity rather than the concentration change of the individual nitrogen oxides.
机译：二氧化钛光催化提供了一种极好的将NOx氧化为硝酸盐并减少空气污染的方法。但是，未改性的二氧化钛在该过程中还会释放出大量有毒的中间二氧化氮，这个问题在以前的文献中很少讨论。本文中，我们通过提供有关许多商业二氧化钛粉末活性和选择性的系统数据来突出显示此问题。还报道了先前开发的掺有W / N的二氧化钛的光催化性能，这首次提供了消除该问题的方法，因为它对硝酸盐表现出极高的选择性。选择性似乎仅取决于钨的含量，4.8原子％的浓度足以诱导非常高的选择性。此外，高选择性也可以通过工业硫酸盐合成工艺得到的W / N掺杂样品来复制。增加的选择性是以绝对活性为代价的，绝对活性低于参比的二氧化钛样品。这就提出了一个问题，当要考虑两个因素（活性和选择性）时，如何正确评估减少NOx的光催化剂。为了解决这个问题，我们建议通过将总的NOx去除率和选择性蒸馏为一个值（即DeNOx指数）来定义一个用于评估NOx减排光催化剂的新品质因数。它是通过为NO和NO2分配毒性值，然后表示总毒性的变化而不是各个氮氧化物的浓度变化而得出的。

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