We report results of a comprehensive study on the effect of bulk defects on the catalytic behavior of Au/TiO₂ catalysts in the CO oxidation reaction, combining quantitative information on the amount of surface and bulk defects from in situ non-contact electrical conductivity measurements after pretreatment and during reaction with information on the electronic/chemical state of the Au nanoparticles (NPs) provided by in situ IR spectroscopy. Treating the catalyst in strongly reducing atmosphere (10% CO/90% N₂) at 400 °C results in a distinct increase in electrical conductivity, indicative of the formation of defects (oxygen vacancies), which are stable at 80 °C in N₂. Long-term kinetic measurements performed at 80 °C show a distinctly lower activity of the bulk reduced catalyst, which increases slowly with time on stream, directly correlated with the decreasing abundance of bulk defects. The detrimental effect of bulk defects on the CO oxidation activity is shown to originate from the lowered CO adsorption strength and hence very low CO_ad coverage on the Au NPs due to electronic metal-support interactions (EMSIs) induced by the presence of TiO₂ bulk defects, in good agreement with our recent proposal (Wang et al., ACS Catal. 7 (2017) 2339). For reaction at −20 °C, EMSIs lead to a promoting effect on the CO oxidation, pointing to a change in the dominant reaction mechanism, away from the Au-assisted Mars-van Krevelen mechanism dominant at 80 °C. The role of EMSIs in the CO oxidation reaction and its temperature dependence is discussed in detail.

我们报告了综合缺陷对Au / TiO ₂催化剂在CO氧化反应中的催化行为的影响的综合研究结果，结合了表面信息和大量缺陷的定量信息，这些定量信息来自原位非接触电导率测量后进行预处理，并在反应过程中通过原位红外光谱提供有关Au纳米粒子（NPs）的电子/化学状态的信息。在400°C的强还原性气氛（10％CO / 90％N ₂）中处理催化剂会导致电导率明显增加，表明形成了缺陷（氧空位），该缺陷在80°C的N中稳定_2个。在80°C下进行的长期动力学测量显示，整体还原催化剂的活性明显较低，随运行时间的增加而缓慢增加，这与整体缺陷数量的减少直接相关。大量缺陷对CO氧化活性的不利影响被证明是由于TiO ₂的存在引起的电子金属-载体相互作用（EMSIs），降低了CO的吸附强度，因此在Au NP上的CO _ad覆盖率非常低。大量缺陷，与我们最近的提议非常一致（Wang等人，ACS Catal.7（2017）2339）。对于在-20°C下的反应，EMSI导致对CO氧化的促进作用，表明主要的反应机理发生了变化，而与在80°C下的Au辅助的Mars-van Krevelen反应机理相反。详细讨论了EMSI在CO氧化反应中的作用及其温度依赖性。