In order to determine directly the quantity “conversion of a catalyst”, we developed a new YSZ solid-electrolyte based mixed-potential sensor that enables to compare electrochemically two gas compartments. Core of the sensor is a self-heated YSZ disc that provides in the center sufficiently high temperatures for sensing. At the sensor rim, the temperatures are low enough to allow for applying polymer sealings to separate both gas chambers gas tightly. In this study, the YSZ sensor disc compares two gas mixtures emulating the propene concentrations that occur up- and downstream of a diesel oxidation catalyst (DOC). At a temperature of 500 °C at the center of the disc, the changing propene concentrations on one side of the sensor, which emulate a changing propene conversion of the catalyst, are reflected by the sensor signal. Up to a conversion of 90 %, the sensor signals follow a theoretical equation that is derived from mixed-potential theory. For higher propene conversions, the signal differs from that theory. An initial explanation for this may be the catalytic activity of the platinum electrode at these high operation temperatures. This is supported by the fact that when reducing the catalytic activity, which is achieved by reducing the sensing temperature, the sensor signal is meeting more and more the theoretically derived equation. At 425 °C and below, there is no more dependency on the feed gas concentration, and all measured data fit exactly with the above-derived theory, i.e., the sensor signal depends only on the “conversion of the catalyst” and not on the propene concentration. As result, a sensor that measures directly the quantity “conversion” is obtained.

为了直接确定“催化剂转化率”的数量，我们开发了一种新的基于YSZ固体电解质的混合电势传感器，该传感器能够对两个气体隔室进行电化学比较。传感器的核心是一个自加热的YSZ圆盘，该圆盘在中心提供足够高的温度进行传感。在传感器边缘，温度足够低，以允许施加聚合物密封以将两个气室紧密地分隔开。在这项研究中，YSZ传感器圆盘比较了两种气体混合物，它们模拟了在柴油氧化催化剂（DOC）的上下游出现的丙烯浓度。在圆盘中央的温度为500°C时，传感器信号反映了传感器一侧的变化的丙烯浓度，该变化模拟了催化剂变化的丙烯转化率。高达90％的转换，传感器信号遵循从混合电位理论推导的理论方程式。对于更高的丙烯转化率，信号不同于该理论。对此的初步解释可能是铂电极在这些高工作温度下的催化活性。这在以下事实中得到支持：当降低催化活性时（通过降低感测温度实现），传感器信号越来越满足理论推导的方程式。在425°C和更低温度下，不再依赖于进料气浓度，所有测量数据均完全符合上述理论，即，传感器信号仅取决于“催化剂的转化率”，而不取决于丙烯浓度。结果，