Two mirror-polished titanium grade 7 plates (Tricor Metals) having a dimension of 13 cm × 13 cm × 1 cm served as current collectors for the module. Positive BPL carbon electrodes were soaked in the 1M NaCl electrolyte solution for 2 h. Negative electrodes were not soaked in the electrolyte. In the stacks, the electrodes were separated by cellulose-based filter papers (Whatman Grade 2, GE Healthcare Life Sciences) having a size of 8 cm × 8 cm size soaked with 1M NaCl solution. Interruption of the ionic current between the two ends of a bipolar electrode was achieved by inserting a titanium sheet (TA2 99% Purity, 8 cm × 8 cm × 0.1 mm), which is impenetrable for the electrolyte. Stacks of 9 cm × 9 cm EPDM rubber sheets (1/16'', McMaster-Carr) with an 8 cm × 8 cm opening were placed between the upper and bottom titanium plates to seal the cell. In order to check the potential distribution within the multi-pair electrode stacks, a titanium strip (0.8 cm × 4.5 cm × 0.1 mm) was inserted between the bottom side of the bipolar electrode and the separator. A 7.5 cm × 7.5 cm sized carbon cloth (AvCarb 1071 HCB) was placed between the negative electrode and the upper plate or the titanium sheet and acted as gas diffusion layer. The upper and bottom plates were then clamped together by 16 electrically insulated set screws. These screws were tightened evenly to 20 in.lb using a torque wrench. The gas was distributed via the radial gas flow system, in which the gas flows from the inlet port in the center to the outlet port in the periphery of the SSA module. To obtain a uniform gas flow through the stack all layered components between the end plates had a circular opening with a diameter of 9 mm. A PTFE tubing (1/32" ID × 1/16" OD) with side openings (1/20" in diameter) was inserted into the channel created by these openings in order to maximize even gas distribution within the stack.