A comprehensive size dependent CO oxidation activity has been demonstrated for Pd-SBA-15 catalysts with Pd NPs of varying sizes such as 1-2, 4-6 and 7-10 nm. Pd-SBA-15 catalyst with smallest sized NPs (Pd-S-N) has been synthesized by modified deposition precipitation method recently developed in our lab. Pd-S-N catalyst (reduced at 400 °C) demonstrated CO oxidation activity with lower light off temperature (60 °C), clearly one of the best reported for a Pd-silica system. A detailed XPS and insitu DRIFTS analyses further supported by XAS and DFT calculations reveal the presence of easily decomposable highvalent Pd-oxide on co-ordinatively unsaturated Pd sites (Pd_cus). Weak binding of CO on Pd_cus sites in small Pd NPs leaving sites for oxygen activation is attributed for the low temperature activity of Pd-S-N for CO oxidation.

对于具有不同尺寸（例如1-2、4-6和7-10 nm）的Pd NP的Pd-SBA-15催化剂，已证明了其与尺寸有关的全面的CO氧化活性。通过我们实验室最近开发的改进的沉积沉淀法合成了具有最小尺寸NPs的Pd-SBA-15催化剂（Pd-SN）。Pd-SN催化剂（在400°C时还原）具有较低的起燃温度（60°C），具有CO氧化活性，显然是Pd-二氧化硅系统中报道最好的催化剂之一。详细XPS和原位DRIFTS分析由XAS和DFT计算进一步支持揭示易分解highvalent钯氧化物的协同ordinatively不饱和位点的Pd的存在（钯_CUS）。在Pd CO的弱结合_CUS 小Pd NP中的位点留有氧活化位点，归因于Pd-SN对CO氧化的低温活性。