This is impossible to answer without knowing what is between the electrodes and exact details of the systems.
You may read the following papers with inspiration of different mechanisms for rectification:
J. Taylor, M. Brandbyge, and K. Stokbro, Theory of rectification in Tour wires: the role of electrode coupling, Phys. Rev. Lett. 89, 138301 (2002).
K. Stokbro, J. Taylor and M. Brandbyge, Do Aviram-Ratner diodes rectify?, J. of Amer. Chem. Soc. 125(13), 3674 (2003).