Functionalized Silicon Electrodes in Electrochemistry
Vinícius R. Gonçales, Jiaxin Lian, Shreedhar Gautam, Richard D. Tilley, J. Justin Gooding
Abstract
Avoiding the growth of SiO x has been an enduring task for the use of silicon as an electrode material in dynamic electrochemistry. This is because electrochemical assays become unstable when the SiO x levels change during measurements. Moreover, the silicon electrode can be completely passivated for electron transfer if a thick layer of insulating SiO x grows on the surface. As such, the field of silicon electrochemistry was mainly developed by electron-transfer studies in nonaqueous electrolytes and by applications employing SiO x -passivated silicon-electrodes where no DC currents are required to cross the electrode/electrolyte interface. A solution to this challenge began by functionalizing Si–H electrodes with monolayers based on Si–O–Si linkages. These monolayers have proven very efficient to avoid SiO x formation but are not stable for a long-term operation in aqueous electrolytes due to hydrolysis. It was only with the development of self-assembled monolayers based on Si–C linkages that a reliable protection against SiO x formation was achieved, particularly with monolayers based on α,ω-dialkynes. This review discusses in detail how this surface chemistry achieves such protection, the electron-transfer behavior of these monolayer-modified silicon surfaces, and the new opportunities for electrochemical applications in aqueous solution.