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

我们已经报道了在PEFC中负载铂催化剂表面覆盖二氧化硅层具有极高的耐久性，但由于二氧化硅层内的缓慢传质，该层可能会限制反应速度。在这项工作中，我们研究了二氧化硅层中的传质，以及涂层催化剂具有优异耐久性的原因。通过改变镀膜条件，成功地控制了二氧化硅层的结构。用甲基三乙氧基硅烷制备的二氧化硅层具有较大的孔径，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，但金属表面与硅层之间的相互作用或硅层的正电荷可能会抑制反应中铂物种的溶解。最后还发现，与未包覆的催化剂相比，包覆后的Pd-Co催化剂对PEFC的阴极具有极高的耐久性。

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.