Two-dimensional nanochannels based on graphene membranes show great potential in applications such as ion separation, fast water transport, and green energy. So far, most studies have been focused on nanochannels using homogeneous wall materials, while the effect of vertically asymmetric wall materials on ion transport has long been overlooked. Here, we report on ion transport properties through asymmetric graphene-SiNx nanochannels. We propose a facile process that leverages simple operations o