We explore the spatiotemporal pattern formation of oscillatory electrodissolution of nickel in sulfuric acid with two micro-wires in an on-chip integrated microfluidic flow cell. In the flow channel, the reference and counter electrodes are placed at the opposite end of the flow channel (contralateral placement). A theory based on modeling the interactions between the reactions indicates that there is a unidirectional negative coupling through the electrode potential from the upstream to the downstream electrodes. Experiments and numerical simulations with a kinetic model show that such unidirectional negative coupling could induce complex dynamics. At small cell resistances the uniform stationary state loses stability and a non-uniform stationary state, or a coupling induced oscillatory state can occur. At large cell resistance the oscillations can produce anti-phase synchrony and complex waveforms. The nature of the unidirectional coupling is confirmed in independent experiments with synchrony analysis. The findings indicate that contralateral placement should be used with great care in electroanalytical application with reactions that exhibit negative differential resistance (NDR) region, e.g., due to passivation or adsorption of an inhibitor. (C) The Author(s) 2018. Published by ECS.