Reduction of the Ohmic Drop

As illustrated in Equation (17.20) for parallel electrodes and a uniform current distribution, the ohmic drop decreases with decrease in the inter-electrode gap and with increase in the electrolyte conductivity. In microstructured reactors, the small interelectrode gap together with the conductivity increase due to the coupling of the electrode processes leads to a substantial reduction in the ohmic perudty [7, 8j. Hence micro-structured designs permit one to minimize the cell voltage [Equation (17.19)], the specific energy consumption of the electrochemical cell [Equation (17.18)] and the heat generation terms [Equation (17.21)]. 

The low ohmic drop reduces the need for supporting electrolyte. Several research teams have shown that it is even possible to work without the addition of a conducting salt [7-11] the resulting processes are referred to as self-supported . The absence of a conducting salt reduces costs since it has neither to be purchased nor removed from the reaction mixture. 

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Now it is possible to assemble microelectrodes with extremely short response times. Nevertheless, an additional problem for the reduction of the ohmic drop is that for short times high currents arise from the large concentration surface gradients. This leads to the use of on-line and real-time electronic compensation of the cell resistance combined with the use of microelectrodes [53]. 

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