The electron tunneling from (to) the redox mediator in the liquid phase, through hBN of varied thickness, to (from) the graphite electrode was realized using devices depicted in Fig. . The basal planes of both graphite and hBN have planar sp 2 hybridization, are chemically inert, and lack dangling bonds. Crucially, their surfaces, which face each other in the resulting heterostructure, are not exposed to any polymer or solvent during the assembly. This ensures that the interface between these two materials is well-defined and atomically-flat and that the tunneling distance between the redox mediator and graphite can be controlled by the number of hBN layers.