Strategies for improving GDE performance by a uniform dispersion of catalyst nanoparticles and an optimal Nafion content

In the context of the strategies needed to mitigate CO2 emissions and combat climate change, the electrochemical CO2 reduction represents a promising alternative. Among the different reactors, GDE-based ones are widely studied systems: here, the limitations shown by configurations with CO2 dissolved in electrolyte solutions can be overcome by feeding CO2 directly in gaseous form. In this work, the manufacturing process of the Cu-based gas diffusion electrode, namely the catalytic ink deposition on a porous carbon paper support, was carried out both by airbrushing (manual) and by spray-coating (automated) techniques. The characterization of the electrodes was performed by using X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) techniques. To assess electrodes behavior, cyclic and linear sweep voltammetry techniques were conducted. When comparing the achieved current densities at the highest applied potential, the electrode obtained with the spray coater displayed a better electrocatalytic activity (~10 mA/cm2 higher at about -2.25 V vs Ag/AgCl), with respect to that fabricated with the airbrush. A thorough study of the GDEs performance was accomplished, testing the so obtained electrodes and thereby evaluating the effect of a variation of Nafion content in the productivity and selectivity results toward the desired products. The catalyst layer dispersion is a critical aspect of electrochemical CO2 reduction and, confirming previous studies on the different deposition methods, a more uniform distribution of the catalyst particles enabled the spray coated GDEs to outperform the hand-made ones. Furthermore, the variation of Nafion content on the GDE structure had a relevant effect on the electrode performance, allowing to considerably reduce the side-production of hydrogen and increasing at the same time the CO generation.