The reactivity of AuPd nanoparticle catalysts prepared by sol immobilisation is often explained by a structure activity relationship based solely on particle size or composition. In this contribution, we compare colloidal AuPd nanoparticles stabilised with polyvinylpyrrolidone (PVP) with the same AuPd nanoparticles supported on TiO₂ for the direct synthesis of hydrogen peroxide and methane oxidation to methanol. We show that while the particles have similar rates of H₂O₂ synthesis, supporting the particles can affect the rates of H₂O₂ decomposition and hence the effectiveness of the catalyst for reactions which rely on H₂O₂ as an initiator or oxidant. We demonstrate that the absence of PVP results in high rates of H₂O₂ decomposition in methane oxidation experiments but this can be minimised by the addition of PVP to the reactor. These results also show that for AuPd alloys, both polymer stabiliser and support effects need to be taken into account when describing the activity of the nanoparticles and the active sites should in fact be thought of as a metal–support–polymer interface with many degrees of freedom.

中文翻译：

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金钯胶体作为过氧化氢合成，降解和甲烷氧化的催化剂：PVP稳定剂的作用

通常通过仅基于粒度或组成的结构活性关系来解释通过溶胶固定化制备的AuPd纳米颗粒催化剂的反应性。在此贡献中，我们比较了用聚乙烯吡咯烷酮（PVP）稳定的胶体AuPd纳米颗粒与负载在TiO ₂上的相同AuPd纳米颗粒，用于直接合成过氧化氢和甲烷氧化为甲醇。我们表明，尽管颗粒具有相似的H ₂ O ₂合成速率，但负载颗粒会影响H ₂ O ₂分解速率，从而影响催化剂对依赖H ₂ O _2的反应的有效性。作为引发剂或氧化剂。我们证明，PVP的不存在会导致甲烷氧化实验中H ₂ O _2的分解率很高，但这可以通过向反应器中添加PVP来最小化。这些结果还表明，对于AuPd合金，在描述纳米颗粒的活性时，必须同时考虑聚合物稳定剂和载体的作用，并且实际上应该将活性部位视为具有许多程度的金属-载体-聚合物界面。自由。