This project aims to develop a novel and optimizable platform for H₂O₂-dependent enzymatic reaction cascades in aqueous as well as organic media. A team of three researchers from different institutes at Hamburg University of Technology (TUHH) works together in an interdisciplinary team to establish a fully controllable electrochemical in situ H₂O₂ synthesis using a novel All-in-One (AiO) electrode, as well as to characterize and optimize enzyme immobilization on the electrode and two model biocatalytic reaction cascades. Hydrogen peroxide (H₂O₂) is a mild and stable oxidant that can easily be produced electrochemically and is already being used as a substrate in many biocatalytic processes. Its application in large-scale industrial processes however is limited by two factors: Firstly, H₂O₂ is produced in an aqueous solution by classical chemosynthesis, introducing water into organic systems and possibly favoring side reactions. Secondly, higher H₂O₂ concentrations result in a detrimental effect on the activity and stability of many enzymes. Therefore, the accurate and tuneable dosage of H₂O₂ into the reaction system is challenging, but of great importance.

In the proposed All-in-One (AiO) electrode setup the in situ production rate of H₂O₂ can be accurately tuned electrically to match the catalytic capacity of the enzymes present in the system. To further increase the proximity of the H₂O₂ production and consumption, the enzymes can be immobilized directly on the electrode producing the H₂O₂. This could potentially keep the H₂O₂ concentration low and reduce the detrimental effect of H₂O₂ on the activity and stability of the enzyme. The H₂O₂ is produced in situ for the biocatalytic step by electrochemical reduction of oxygen at the anode followed by conversion to H₂O₂ at the cathode. The AiO electrode consists of an inner chamber, where the oxygen is generated at the anode and passes through the cathode by a pressure gradient, where it is converted to H₂O₂. This is possible because the cathode is made out of a highly porous carbon foam backbone called Globugraphite, coated with carbon nanotubes (CNTs). Both materials show a high specific surface area and are tuneable in their micro-and macroscopic configuration layout, encompassing an increased potential for high H₂O₂ production rates as well as efficient enzyme immobilization. With its unique layout of the inner chamber and outlying gas diffusion cathode, the complete AiO electrode can be mounted into a reactor set up similarly to a pH or pO₂ probe, making it applicable to a wide range of reactor setups and scale-up scenarios.