Alanine Formation in a Zero‐Gap Flow Cell and the Role of TiO<sub>2</sub>/Ti Electrocatalysts
Christos Englezos, Akash Raman, Dirk Jonker, Norma A. Ramos Delgado, Marco Altomare, Han Gardeniers, Arturo Susarrey‐Arce
Abstract
Abstract The electrochemical synthesis of ‐amino acids at room temperature and pressure is a sustainable alternative to conventional methods like microbial fermentation and Strecker synthesis. A custom‐built zero‐gap flow electrolyzer was used to study the electrosynthesis of alanine via the electrocatalytic reductive amination (ERA) of the corresponding biomass‐derivable ‐keto acid precursor – pyruvic acid (PA), and hydroxylamine (NH 2 OH) at very low pH. Non‐toxic, abundant, and easy to prepare TiO 2 /Ti electrocatalysts were utilized as the cathode. Three TiO 2 /Ti felt electrodes with different oxide thicknesses were prepared and their characterization results were correlated with their respective electrochemical performance in terms of Faradaic efficiency , and partial current density . Cyclic voltammetry indicated a different electrocatalytic reduction process on hydrothermally treated electrodes, compared to thermally oxidized ones. Hydrothermally treated electrodes were also found to have the thickest porous anatase layer and achieved 50–75 % alanine conversion efficiencies. Optimization showed that the cell potential, reactant flow rate and the PA: NH 2 OH ratio were crucial parameters in determining the conversion efficiency. and were found to significantly decrease when an excess of is used and, an optimal alanine of 75 % was achieved at 2.0 V applied cell potential and 10 mL/h reactant flow rate.