It is instructive to consider the properties of the tunneling barrier and its dependence on the hBN thickness and applied potential. The band diagram in Fig. schematically depicts the various energy levels in the graphite/1L hBN/liquid heterostructure and their mutual alignment for the unbiased case prior to contact between the three phases. Fig. shows the tunneling process for the [IrCl 6 ] 3-oxidation, with a large positive potential applied to the graphite allowing the electrons to tunnel from the occupied states of [IrCl 6 ] 3-to the empty states in graphite. Similarly, Fig. shows the electron tunneling from the occupied states in graphite to the empty states of [Ru(NH 3 ) 6 ] 3+ , facilitated by the large negative potential applied to the graphite. An important implication of the analysis in Figs. is that both processes are dominated by the electron/hole tunneling near the valence band maximum (VBM), rather than the conduction band minimum (CBM), of hBN, since this path has a significantly lower tunneling barrier. Furthermore, the barrier for tunneling to/from [IrCl 6 ] 3-is smaller than that for [Ru(NH 3 ) 6 ] 3+ thanks to the relative position of the redox levels and VBM of hBN.