(245g) Automated Microfluidic Platform for Rapid Screening Reaction Conditions for Alcohol Electro-Oxidation

Electro-oxidation of alcohols, coupled with hydrogen evolution, stands out as a promising green synthesis approach for sustainable chemical and fuel production. Though continuous-flow reactors are considered as scalable options for these reactions, optimizing their conditions is time-consuming and costly. To address this, we have developed an automated platform integrating a 3D-printed electrochemical microfluidic reactor, micromixer, pumps and in-operando electrochemical and optical measurements. Automated screening of various reaction conditions is achieved by controlling and synchronizing all devices through a Python program. As a representative reaction, we examined the electro-oxidation of cyclohexanol at a nickel electrode in an alkaline electrolyte. The flow pattern was firstly examined to minimize reactant crossover in the membrane-less reactor design. Our results showed that current density increased from 4.5 mA/cm² to 7.1 mA/cm² with increasing the applied potential from 0.45 V to 0.49 V (vs. Ag/AgCl), when using electrolyte of 0.5 M NaOH containing 40 mM cyclohexanol at a flow rate of 0.9 mL/min. Increasing cyclohexanol concentration from 14 mM to 67 mM increased the current density by up to 97%. Increasing the flow rate to 4.4 mL/min increased current density by up to 12%, suggesting enhanced cyclohexanol transfer and removal of oxidized products at the electrode. These improvements indicated a mixed-controlled mechanism for the reaction. Finally, three types of surfactants were screened as additives, which can be absorbed at the electrode-electrolyte interface to regulate the electro-oxidation process. Ionic surfactants, including sodium dodecyl sulfate and cetyltrimethylammonium bromide, were found to reduce current density by up to 10% as surfactant concentration increased from 1.3 mM to 6.7 mM, while the non-ionic surfactant TritonX-100 increased current density by up to 12%. This automated microfluidic platform has been proven to be an effective tool for accelerating the understanding and design of alcohol electro-oxidation processes.