Kinetic Study on Superior Performance of Silica-Coated Cathode Catalysts for PEFC

我们已经报道，负载Pt催化剂覆盖的二氧化硅层显示出极高的耐久性的阴极在PEFC，但该层可能会限制反应速率，由于缓慢的质量传递内的二氧化硅层。本文研究了硅层中的传质过程和涂层催化剂具有上级耐久性的原因。 通过改变涂覆条件，成功地控制了氧化硅层的结构。使用甲基三乙氧基硅烷制备的二氧化硅层具有较大的孔径，并表现出高活性和高耐久性。 涂层催化剂表现出高耐久性的原因尚不清楚，但金属表面与二氧化硅层之间的相互作用或二氧化硅层的正电荷可能抑制反应期间Pt物种的溶解。 最后，还发现与未涂覆的催化剂相比，涂覆的Pd-Co催化剂在PEFC中显示出极高的阴极耐久性。

We have reported that supported Pt catalysts covered with silica layer showed extremely high durability for the cathode in PEFC, but the layer might limit reaction rate due to slow mass transfer within the silica layer. In this work we studied on the mass transfer in silica layer and on the reason for the superior durability of the coated catalyst. The structure of silica layer was successfully controlled by changing coating condition. The silica layer prepared using methyltriethoxysilane has larger pore size and exhibited both the high activity and high durability. The reason why the coating catalysts show high durability could not be revealed, but the interaction between metal surface and silica layer, or positive charge of silica layer might suppress the dissolution of Pt species during reaction. Finally, it was also found that the coated Pd-Co catalysts showed extremely high durability for the cathode in PEFC, as compared with uncoated catalysts.