Effects of Electrode Support Structure on Electrode Microstructure, Transport Properties, and Gas Diffusion within the Gas Diffusion Layer

Abstract

The effects of gas diffusion layer (GDL) and electrode microstructure, which influence the catalyst layer and catalyst–membrane interface on the performance of a membrane electrode assembly (MEA) for gas-phase electrolysis and the separation of CO 2 were experimentally characterized. Several types of GDL materials, with and without a microporous layer (MPL), were characterized using scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area analysis. The diffusion of reactants through the GDL materials was measured to determine the effects on the microstructure and chemical properties on mass transport. The effects on the GDL structure and chemistry were determined through evaluation of Pt–IrO 2 MEAs with different GDL materials using constant-current measurements. Increasing the thickness of the MPL and hydrophobicity within the GDL assist with retaining water within the membrane and catalyst layers, which results in greater performance at high current densities.

Systematic screening of gas diffusion layers for high performance CO2 electrolysis

“…The hydrophobicity of the GDE is clearly a critical parameter, as indicated by several earlier studies 11 , 17 , 36 . To investigate whether a highly hydrophobic CFL can be sufficient for selective CO 2 RR, we studied the effect of the PTFE content on the CO 2 RR in the Toray carbon papers subgroup (Fig.…”

“…The effects of the physical parameters of the GDL (thickness, CFL, MPL) and PTFE content of the CFL and/or MPL on the mass transport of the reactants into and out of the catalyst layer have also been studied 36 . The general conclusion from these scarce studies was that the wetting properties of different GDLs affect the flooding of the GDEs during CO 2 RR, that is the accumulation of water in the GDE, leading to decreased selectivity and/or cell performance 22 , 37 .…”

Carbon corrosion in low-temperature CO2 electrolysis systems

“…70 On the anode, Schwartz et al found that thicker GDLs exhibited superior performance and attributed this to the their ability to retain water within the membrane and catalyst layers. 72 Further research in this area is needed to develop structure-performance relationships for GDLs and rationally design anodes for CO 2 electrolysis. It is possible that carbon-based anode GDLs with reasonable lifetimes could be developed in the future, but they are not currently on the market today.…”

Non-invasive current collectors for improved current-density distribution during CO2 electrolysis on super-hydrophobic electrodes

“…Contrary to ePTFE electrodes, carbon GDL’s have the advantage of being conductive (albeit with a much higher through-plane conductivity than the in-plane conductivity) 25 , 26 . The disadvantage of these electrodes, however, is the flooding of the micro-porous layer.…”