Electrochemical identification and quantification of through‐plane proton channels in graphene oxide membranes

Stacked graphene oxide (GO) proton membranes are promising candidates for use in energy devices due to their proton conductivity. Identification of through‐plane channels in these membranes is critical but challenging due to their anisotropic nature. Here, we present an electrochemical reduction method for identifying and quantifying through‐plane proton channels in GO membranes. The simplicity lies in the operando optical observation of the change in contrast as GO is electrochemically reduced. Here, we find three proton‐dominated three‐phase interfaces, which are critical for the reduction reactions of GO membranes. Based on these findings, a method is proposed to identify and quantify through‐plane channels in stacked GO proton membranes using a simple three‐electrode device in combination with real‐time imaging of the membrane surface.