Protonated weak acids commonly used in microbial electrolysis cell (MEC) solutions can affect the hydrogen evolution reaction (HER) through weak acid catalysis, and by lowering solution resistance between the anode and the cathode. Weak acid catalysis of the HER with protonated phosphate, acetate, and carbonate electrolyte species improved MEC performance by lowering the cathode's overpotential by up to 0.30 V at pH 5, compared to sodium chloride electrolytes. Deprotonation of weak acids into charged species at higher pHs improved MEC performance primarily by increasing the electrolyte's conductivity and therefore decreasing the solution resistance between electrodes. The potential contributions from weak acid catalysis and solution resistance were compared to determine whether a reactor would operate more efficiently at lower pH because of the HER, or at higher pH because of solution resistance. Phosphate and acetate electrolytes allowed the MEC to operate more efficiently under more acidic conditions (pH 5). Carbonate electrolytes increased performance from pH 5 to 9 due to a relatively large increases in conductivity. These results demonstrate that specific buffers can substantially contribute to MEC performance through both reduction in cathode overpotential and solution resistance.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Energy Engineering and Power Technology
- Physical and Theoretical Chemistry
- Electrical and Electronic Engineering