Impact of the Native SiO_2 Surface Layer on the Electron Transfer at Amorphous Si Electrodes

摘要

The electron transfer at uncharged microstructured and planar amorphous (a-)Si was characterized using the feedback mode of scanning electrochemical microscopy (SECM) and 2,5-di-tert-butyl-1,4-dimethoxybenzene as redox mediator in carbonate electrolytes. Approach curves and images demonstrate that the electron transfer rate at pristine a-Si is relatively small due to the native SiO_2 surface layer. In addition, the electron transfer rates show local variations because of the heterogeneous coverage of SiO_2. After removal of the SiO_2 layer, the effect of the solid electrolyte interphase (SEI) on electron transport rate can be studied. The SiO_2 layer is at least partially removed by approach curve contact and scratching with the microelectrode probe. After SiO_2 removal, the electron transfer rates increase strongly and remain heterogeneous.