A supersensitive test (SST) for photocatalytic activity is described, based on ISO 22197-1:2016 for the removal of NO, i.e. the standard NO removal ISO. The key reaction is the photocatalysed oxidation of nitric oxide (NO) to nitrogen dioxide (NO₂) by oxygen, which, for most materials, is the dominant reaction at the end of the 5 h irradiation period employed in the standard ISO. The SST uses the same photoreactor as the standard NO ISO, but with 3 (instead of 1) sample pieces and a flow rate of 0.25 L min⁻¹ (instead of 3 L min⁻¹) and, as a consequence, is 36 x’s more sensitive than the standard ISO. The SST is used to assess the activities of materials that show little if any activity when tested using the standard ISO, such as commercial self-cleaning samples (such as glass (Activ™), paint and plastic), as well as bank notes. An expression is derived, and verified using films of P25 powder, which relates rate, and so photocatalytic activity, directly to the average %NO removed, measured under either standard ISO or SST conditions, in the last 15 min of irradiation, i.e. %NO_rem, where the latter value is directly related to the photocatalytic area, A, and the reciprocal of the flow rate, 1/f. This relationship allows all %NO_rem values < 25 %, measured using either standard ISO or SST conditions, to be combined to create a universal scale of photocatalytic activity. The universal scale of activity is illustrated using the calculated %NO_rem values for high, medium and low activity materials which spans over 3 orders of magnitude of activity. The possible uses of this scale are discussed briefly.

基于ISO 22197-1：2016描述了一种用于光催化活性的超灵敏测试（SST），用于去除NO，即标准NO去除ISO。关键反应是氧气将一氧化氮（NO）光催化氧化为二氧化氮（NO ₂），对于大多数材料而言，这是标准ISO中所用的5小时照射期结束时的主要反应。所述SST使用相同的光反应器为标准ISO NO，但与3（而不是1）的样品片和0.25升min的流速^-1（而不是3升分钟^-1），并且作为结果，是36×的比标准ISO更敏感。在SST用于评估使用标准ISO测试时几乎没有活性的材料的活性，例如商业自清洁样品（例如玻璃（Activ™），油漆和塑料）以及钞票。使用P25粉末薄膜得出表达式并进行验证，这与速率和光催化活性直接相关，在照射的最后15分钟内，在标准ISO或SST条件下测量的去除的平均NO的百分比即％NO _rem，后者的值与光催化面积A和流速的倒数1 / f直接相关。此关系允许使用标准ISO或SST测量的所有％NO _rem值<25％的条件下，结合起来以创建通用规模的光催化活性。使用计算出的高，中和低活性物质的％NO _rem值说明了活动的普遍规模，这些物质的活性跨越三个数量级。简要讨论了该量表的可能用途。