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Tubular hollow fibre electrodes for CO2 reduction made from copper aluminum alloy with drastically increased intrinsic porosity
Electrochemical reduction of CO2 to higher-order hydrocarbon products offers a significant contribution to the challenge of a circular economy. In the pursuit of better copper metal catalyst, it was early on realized that increasing productivity of copper catalysts systems is reliant on high surface area per volume. Tubular gas diffusion electrodes offer such properties. In this work, we present a methodology to fabricate tubular hollow fibre copper electrodes with drastically increased intrinsic porosity. Our described method utilizes a standard dealloying process of copper aluminium particles to induce an intra-particle nanoporosity. The specific surface area increases from 0.126 m2 g−1 before dealloying to 6.194 m2 g−1 after dealloying. In comparison to conventional planar copper electrodes and literature data from conventional copper hollow fibres, the intra-particle porosity leads to a drastically increase in electrochemical activity. Electrochemical measurements reveal increased current densities at low over-potentials in comparison to conventional copper electrodes under identical experimental conditions emphasizing the significant impact of the porosity on the electrode performance. The presented method can be easily transferred to other alloy particles, highlighting its versatility for electrode fabrication. © 2019 The Author(s
A falling film design for electrochemical CO2 reduction
Utilizing CO2 as a resource for CO production in electrochemical reactors requires gas diffusion electrodes (GDE) that maintain a stable and highly reactive gas/liquid/solid interface. When scaling the process towards industrial application, the pressure difference in the electrolyte channel increases, amplifying instabilities at the multi-phase boundary inside the GDE. To tackle this challenge, a falling film design where the electrolyte is solely driven downwards by gravity is presented in this work. The hydrostatic pressure is then counter weighed by the hydrodynamic pressure drop, leading to a constant pressure between gas and liquid side over the height of the electrode. Three 3D-printed electrolyte frame designs were compared in a flow cell regarding the liquid distribution in the channel. An even distribution could be achieved with 2 mm channel thickness at an electrolyte flow rate of 4000 mL min−1. Electrolysis experiments were carried out using a 100 cm2 silver GDE. Compared to a conventional electrolyte frame design, the falling film design yielded stable process conditions with a Faraday Efficiency to CO of up to 90 % at 100 mA cm−2 and a cell voltage of 5.5 V. The presented design presents a pathway for scaling CO2 electrolyzers in height and sustains a stable long-term process