Electrochemical Co-Production of Hydrogen, Base and Acid from Low-value Brines via Direct Electrosynthesis
Hydrogen production is of growing interest as a low-carbon alternative fuel. However, most of the hydrogen is still produced from fossil fuels. In contrast, brine electrolysis offers a promising route to produce hydrogen and other valuable byproducts. However, the conventional method for producing acid and base simultaneously using bipolar-membrane electrodialysis (BMED), consumes significant energy and has a complexed configuration. Additionally, it is important to suppress chlorine evolution and produce HCl instead in brine electrolysis. This study investigates the performance and economic viability of three different brine electrolysis systems: direct electrosynthesis (DE) without a bipolar-membrane, anion exchange membrane (AEM), and cation exchange membrane (CEM) systems, using a new Manganese-Molybdenum coated titanium electrode that suppresses Cl2. Results show that the DE-MnMo/Ti electrode system produced 0.005 mol of H2, 0.0041 mol of O2, 0.37 M NaOH, and 0.2 M HCl. Compared to pure water electrolysis, brine electrolysis offers higher economic potential due to the production of value-added products such as O2, NaOH and HCl. Using the DE-MnMo/Ti electrode system and brine, the revenue generated per year is 4 times higher than that of alkaline electrolysis using pure water. Additionally, a life cycle assessment (LCA) is conducted to evaluate the environmental impacts of the DE-MnMo/Ti system. The LCA analysis showed that the DE-MnMo/Ti system can reduce greenhouse gas emissions, energy use, and water usage. Therefore, this study highlights the potential for brine electrolysis with the DE-MnMo/Ti electrode system as an economically viable and environmentally sustainable route for producing hydrogen and high value co-products such as NaOH, HCl, and O2.