The Effects of Catalyst Layer Deposition Methodology on Electrode Performance

Abstract

The catalyst layer of the cathode is arguably the most critical component of low‐temperature fuel cells and carbon dioxide (CO2) electrolysis cells because their performance is typically limited by slow oxygen (O2) and CO2 reduction kinetics. While significant efforts have focused on developing cathode catalysts with improved activity and stability, fewer efforts have focused on engineering the catalyst layer structure to maximize catalyst utilization and overall electrode and system performance. Here, we study the performance of cathodes for O2 reduction and CO2 reduction as a function of three common catalyst layer preparation methods: hand‐painting, air‐brushing, and screen‐printing. We employed ex‐situ X‐ray micro‐computed tomography (MicroCT) to visualize the catalyst layer structure and established data processing procedures to quantify catalyst uniformity. By coupling structural analysis with in‐situ electrochemical characterization, we directly correlate variation in catalyst layer morphology to electrode performance. MicroCT and SEM analyses indicate that, as expected, more uniform catalyst distribution and less particle agglomeration, lead to better performance. Most importantly, the analyses reported here allow for the observed differences over a large geometric volume as a function of preparation methods to be quantified and explained for the first time. Depositing catalyst layers via a fully‐automated air‐brushing method led to a 56% improvement in fuel cell performance and a significant reduction in electrode‐to‐electrode variability. Furthermore, air‐brushing catalyst layers for CO2 reduction led to a 3‐fold increase in partial CO current density and enhanced product selectivity (94% CO) at similar cathode potential but a 10‐fold decrease in catalyst loading as compared to previous reports.

Gold Nanoparticles on Polymer‐Wrapped Carbon Nanotubes: An Efficient and Selective Catalyst for the Electroreduction of CO2

“…We performed these tests in a previously reportedm icrofluidic CO 2 electrolysis cell (Figure 1), [16] using gas diffusion electrodes (GDEs) that were covered with the different catalysts,a ll at identical metal loading (0.17 mg Au cm À2 ), andd epositedu sing an automated airbrush method. [17] The resultsinFigure 3show that under ambient conditions the different Au-based catalysts yield different partial current densities for CO production.T he lowest current densities for CO are found with the Au particles deposited directly onto the GDE surfaces. Increasingly higherp artial current densities for CO are achieved for the Au-based catalysts supportedo nC B( CB/Au), supported on polymer-wrapped CB (CB/ PyPBI/Au), and supported on polymer-wrapped MWNT (MWNT/PyPBI/Au).…”

“…The Faradaic efficiencya nd partial current density calculations were performed according to the procedure described earlier. [17] …”

“…At cathode potentials exceeding À1.5 V, ad rop in the selectivity for CO is apparent for all Aubased samples.I np art, this can be explained by the increased evolution of H 2 ,w hose production is known to be catalyzed by carbon supports at these potentials. [17] Also, large amountso f gaseous CO and H 2 are produced at these cathode potentials leadingt ot he formation of bubbles in the flow cell, possibly lowering the amount of reaction products that is recorded in the GC analysisoft he product mixture.…”

Review—Electrochemical Growth of Carbon Nanotubes and Graphene from Ambient Carbon Dioxide: Synergy with Conventional Gas-Phase Growth Mechanisms

“…Catalysts such as Hg, Pb, metal oxides, metal organic frameworks, and Sn have demonstrated the ability to produce formic acid with respectable faradaic efficiencies, 47,48 while copper catalysts uniquely produce hydrocarbons 49 and silver catalysts are state of the art for CO production. 6,50 Whereas methanol is arguably the most desirable chemical produced through the hydrogenation of CO 2 due to its wide range of applications including direct use as fuel, its production is severely limited by the low faradaic efficiencies. 51,52 The rationale for CO 2 -derived production is also undermined by an extremely low current cost of a few USD/gallon.…”

Composition and Manufacturing Effects on Electrical Conductivity of Li/FeS2Thermal Battery Cathodes

“…We apply techniques from previous studies, such as microcomputed tomography (MicroCT) for three-dimensional (3D) microstructure characterization [9][10][11][12][13][14][15] of highly irregular geometries for use in numerical models. [16][17][18][19] Our approach differs from prior research on FeS 2 thermal battery cathode materials because we perform an integrated investigation of the process-microstructureprocess-performance relationship without relying on empirical data.…”