Functionalized Porous Carbon Fiber Electrodes for Applications in Electrochemical Flow Cells

Abstract: Corrosion of metals in close-loop cooling or heating systems originates from tiny leakages at joints releasing oxygen into the thermal fluids. The presence of dissolved oxygen (DO) in thermal fluids, such as water with various additives forms a rust coating and some rust particles are released in the fluids and accumulate in an undesired place. Overall, these phenomena decrease the efficiency of heat exchangers and boilers in energy systems. There are various techniques to remove DO but each has drawbacks either related to their efficiency, cost, or minimum DO level reachable. Herein, we propose an electrochemical technique to achieve a low-cost and efficient deoxygenation. We investigate both the fundamentals and make a proof of concept for a deoxygenation electrolyser that consumes the DO through the oxygen reduction reaction (ORR). First, we designed a simple and low-cost flow-through electrode by adding macro-porous carbon fiber papers (CFPs) with calibrated loads of carbon microporous particles (CPs) to combine both a high surface area and an open structure for good fluid dynamics. Then, the faradic performance of carbon electrodes is evaluated in a designed static deoxygenation electrolyser that shows three regimes of complex kinetic side reactions involving various species such as O2, H2O2, H2O, and anodic carbon oxidation. The functionalization of redox-active quinone molecules operating by electron mediators over the anode electrode is developed to improve the ORR efficiency and remove the issue of degradation of the carbon anode. Finally, we investigate the use of a new electrocatalytic polymer poly(benzimidazobenzophenanthro-line) (BBL) to drive the ORR toward water instead of forming H2O2. The combination of both the polymer catalyst at the cathode and the quinone molecules designs a path for an efficient deoxygenation electrolyser that could become a key device to slow down corrosion rate and improve the efficiency in energy systems.