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Abstract

Cement production releases 2.5 billion tonnes of CO₂ annually, about 8% of global greenhouse gas emissions. The majority of the CO₂ is released during the first of two high-temperature reactions, calcination, which converts raw limestone (CaCO₃) into lime (CaO), an intermediate in cement production. Calcination emits a stoichiometric amount of carbon dioxide and is usually fueled by the combustion of coal. However, the calcination step can also be accomplished electrochemically by manipulating pH. Electrochemical flow reactors (electrolyzers) that perform this transformation have been demonstrated at lab scale, but have suffered from high cell voltages, low durabilities, or both. Herein, I present an electrolyzer that enables durable electrochemical production of cement precursors. In this thesis, I address two challenges that prevent scaleup of cement electrolyzers. I demonstrate that a cation exchange membrane modified with poly(aniline) resolves the issue of internal salt accumulation that limited previous electrolyzers to under one hour of stable operation. I also investigate the use of an organic redox mediator that can be reduced and oxidized several times at low voltage in aqueous solution to effect the transformation of CaCO₃ into Ca(OH)₂, a precursor for production of cement.