An open source electrochemical channel flow cell setup for kinetics studies. Application to investigations on oxygen electrocatalysis

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Herein, an electrochemical channel flow cell setup that allows for conducting electrochemical investigations up to 80°C and pressurized gases up to 3 bar is presented in details, including technical drawings and list of parts, in an attempt to facilitate the adoption of such setup by the community for electrochemical/electrocatalytic kinetic studies. The oxygen reduction reaction (ORR) on a commercial Pt/C catalyst, chosen as a model reaction, was investigated to demonstrate the reliability of the experimental setup, including the hydrodynamic properties, to provide hands on practical guidelines to carry out experiments, and, on the other hand, to illustrate the capabilities of this electrochemical setup for an assessment of basic quantities. Among the various quantities that have be determined experimentally for the ORR, a monotonic decay of the activation enthalpy and bell-shaped variation of the entropy of activation were resolved as the overpotential for the ORR increases. These fundamental thermodynamic/kinetic data are briefly discussed within the frame of the established reaction mechanism and can serve as a feed for the benchmarking of the outputs from theoretical/computational models. Furthermore, a remarkable agreement was obtained between the change in the activation free Gibbs energy determined for the ORR with the flow cell setup and the kinetic region of fuel cell polarization curve obtained with the same Pt/C catalyst embedded in the cathode of an a hydrogen proton exchange membrane fuel cell. This enables potentially a bridge of the environmental gap existing between model experiments conducted at active material level in contact with liquid electrolyte and experiments with porous gas diffusion electrode embedding the same active material that are employed in practical device.