[Ru(NH 3 ) 6 ] 3+ reduction on hBN does not exhibit as clear a decrease in α with the tunneling distance but yields unusually small values of α between 0.13 and 0.27. Another striking observation shown in Fig. and is that the normalized j lim does not reach the expected unity maximum at large potentials and instead decreases progressively with increasing tunneling distance. This is true for [IrCl 6 ] 3-with 5L hBN, and for [Ru(NH 3 ) 6 ] 3+ with all hBN thicknesses. The small <15% decrease in [IrCl 6 ] 3-j lim on 1-4L hBN can be attributed to the previously discussed contamination at the hBN/graphite interface.