Jason Keonhag Lee

University of Victoria | UVIC · Department of Mechanical Engineering

To enable gigawatt-scale deployment of proton exchange membrane water electrolysers (PEMWEs), drastic reductions from current iridium loadings of 2–3 mg Ir cm ⁻² to less than 0.4 mg Ir cm ⁻² must occur due to iridium's high cost and scarcity. State-of-the-art systems use these high loadings to compensate for degradation experienced over prolonged o...

Heterogeneity within electrochemical devices, such as fuel cells, influences their performance and durability in ways that are not fully understood. 4-dimensional (4-D; 3 spatial dimensions and time) operando visualization techniques such as X-ray (1-2) and neutron (3) tomography are powerful tools to probe heterogeneity within operating electroche...

The performance of electrochemical energy devices, such as fuel cells and batteries, is dictated by intricate physiochemical processes within. To better understand and rationally engineer these processes, we need robust operando characterization tools that detect and distinguish multiple interacting components/interfaces in high contrast. Here, we...

The limited availability of iridium in the Earth’s crust poses severe challenges to establishing gigawatt-scale electrolyzers that are needed for energy storage; this problem urgently calls for reduced iridium loadings. Reducing iridium loadings requires catalyst structure optimization, but to date, little attention has been paid to the characteriz...

Proton-exchange-membrane (PEM) water electrolyzers are promising technologies for generating clean hydrogen for use in a variety of sectors. The anode catalyst layer/porous-transport layer (CL/PTL) interface plays a vital role in determining performance of proton-exchange-membrane (PEM) water electrolyzers. This interface impacts ohmic, kinetic, an...

Water management in a fuel cell is an essential prerequisite for achieving high cell performance, where sufficient water is required for membrane hydration while excess liquid water leads to undesired mass transport losses. Existing heterogeneity within the fuel cell, such as those created by flow-field lands and channels create three-dimensional (...

Developing clean energy technologies, such as polymer electrolyte membrane electrolysis (PEMWE), is essential to mitigate the negative impacts of climate change. However, one persistent barrier to PEMWE uptake is high catalyst costs, which can account for up to 47% of total stack costs [1]. This makes the catalyst a key target for cost savings via...

Electrolytic carbon dioxide (CO2) reduction is becoming increasingly promising for managing anthropogenic CO2 emissions; however, issues related to unstable performance and ineffective gas management are still not fully accounted for in the field. Here, we identify two instability modes that are directly linked to the electrolyte layer gas saturati...

The operating temperature is a critical parameter for improving the performance of a carbon dioxide electrolyzer. Specifically, the power density reduced by up to 35% (at 215 mA/cm²) when increasing the operating temperature from 25 °C to 60 °C, and increasing the cell temperature led to significantly lower ohmic resistances and mass transport limi...

PEM Electrolysis In article number 2100630, Aldo Sau Gago and co-workers develop novel porous transport layers for proton exchange membrane water electrolyzers, allowing operation under extreme conditions of current density, temperature, and pressure. By optimizing the water/gas transport properties of this component, a flow field in the bipolar pl...

A prominent technology for green hydrogen generation is the polymer electrolyte membrane (PEM) electrolyzer. However, the energy efficiency of PEM electrolyzers must improve dramatically to become economically competitive. Here, we engineer the wettability of commercial porous transport layers (PTLs) to make them superhydrophilic. We find that the...

Hydrogen produced via water electrolysis powered by renewable electricity or green H2 offers new decarbonization pathways. Proton exchange membrane water electrolysis (PEMWE) is a promising technology although the current density, temperature, and H2 pressure of the PEMWE will have to be increased substantially to curtail the cost of green H2. Here...

Carbon dioxide (CO2) reduction flow cells, coupled with renewable energy sources, are a promising means of curtailing anthropogenic CO2 emissions by reducing CO2 to generate useful carbon fuels. However, unstable mass transport overpotential due to gas evolution impedes high current density operation (>200 mA cm-2), preventing wide-scale commercial...

Tailoring the catalyst layer interface is paramount for high performance electrochemical energy conversion, from fuel cells to carbon dioxide electrolyzers. Here, we tailored the catalyst layer (CL) interfacial contact in a polymer electrolyte membrane (PEM) water electrolyzer with bilayer titanium mesh porous transport layers (PTLs). In contrast t...

Bubbles are bad news for electrolysis due to undesired overpotentials, though their impact may be even further reaching than previously understood. In a recent report in Energy & Environmental Science, Kempler and researchers control the microstructure of electrodes to minimize overpotentials caused by bubbles in a photoelectrochemical cell.

Polymer electrolyte membrane water electrolysis (PEMWE) is the most promising technology for sustainable hydrogen production. However, it has been too expensive to compete with current state-of-the-art technologies due to the high cost of titanium bipolar plates (BPPs) and porous transport layers (PTLs). Here, we report a high-performance, durable...

Decarbonizing society’s energy infrastructure is foundational for a sustainable future and can be realized by harnessing renewable energy for clean hydrogen and on-demand power with fuel cells. Here, we elucidate how graded porous transport layers (PTLs) are instrumental for high performance gas evolving electrochemical energy conversion devices, w...

Despite the advantages of CO2 electrolyzers, efficiency losses due to mass and ionic transport across the membrane electrode assembly (MEA) are critical bottlenecks for commercial-scale implementation. In this study, more efficient electrolysis of CO2 was achieved by increasing cation exchange membrane (CEM) hydration via the humidification of the...

Mass transport losses ultimately suppress gas evolving electrochemical energy conversion technologies, such as fuel cells and carbon dioxide electrolyzers, from reaching the high current densities needed to realize commercial success. In this work, we reach ultrahigh current densities up to 9 A/cm2 in a polymer electrolyte membrane (PEM) water elec...

The mass transport in porous transport layers (PTLs) with pores exclusively in the through-plane direction was investigated using concurrent in operando X-ray radiography and electrochemical performance analysis. We observed via synchrotron X-ray imaging that through pores situated under the lands are inaccessible to liquid water. We thereby observ...

Reaching high current densities is absolutely imperative for electrochemical energy conversion, from fuel cells to CO2 reduction. Here, we identify the existence of a performance indicator for gas-evolving electrochemical energy conversion devices: the critical current density. The critical current density pinpoints a performance inflection point w...

In this work, we investigated the impact of temperature on two-phase transport in low temperature (LT)-polymer electrolyte membrane (PEM) electrolyzer anode flow channels via in operando neutron imaging and observed a decrease in mass transport overpotential with increasing temperature. We observed an increase in anode oxygen gas content with incre...

The need for capturing CO 2 has become urgent with a record-breaking concentration of CO 2 in our atmosphere (average of 407.4 ppm in 2018 [1]). CO 2 electrolyzers are a promising technology capable of achieving a net-negative CO 2 cycle when coupled with renewable energy sources. Aqueous electrolyte-based alkaline CO 2 electrolyzers have recently...

The electrochemical reduction of CO2 is promising for mitigating anthropogenic greenhouse gas emissions; however, voltage instabilities currently inhibit reaching high current densities that are prerequisite for commercialization. Here, for the first time, we elucidate that product gaseous bubble accumulation on the electrode/electrolyte interface...

Here, we elucidated the dynamic gas transport behavior in the anode porous transport layer (PTL) of polymer electrolyte membrane (PEM) electrolyzers via in operando synchrotron X-ray imaging. The imaging results showed that the gas saturation in the PTL reached steady state more rapidly with a steep current density ramp-up and a shallow ramp-down (...

In this work, we designed sintered titanium powder-based porous transport layers (PTLs) for polymer electrolyte membrane (PEM) electrolyzers by tailoring the powder diameter and porosity via a new approach. We examined how the PTL powder diameter and porosity influence reactant transport and PTL-catalyst layer (CL) interfacial contact by using a st...

We investigate the temperature-dependent gas saturation in the porous transport layer (PTL), and the subsequent impact of this gas saturation on the mass transport overpotential of a polymer electrolyte membrane (PEM) electrolyzer. Via in operando neutron imaging of a PEM electrolyzer, we observe that increasing the operating temperature results in...

A novel analytical model was derived for the first time to predict the substrate oxygen transport resistance as a function of local saturations in the substrate region under the channel (region C) and the substrate region under the land (region L). Prior to this work, the state-of-the-art was limited to correlating bulk substrate oxygen transport r...

Optimizing the porous transport layer (PTL) structure is crucial for high current density operation of polymer electrolyte membrane (PEM) electrolyzers. Previous studies from the literature demonstrated that PTL structures, mainly porosity and titanium powder diameter, can be strategically chosen to improve the performance (1-3). However, transport...

The porous transport layer (PTL) is a key component in the polymer electrolyte membrane (PEM) electrolyzer for transporting reactant liquid water to the active sites while facilitating oxygen gas removal. Most current PTL designs use an expanded foam structure with uniform porosity. The interactions between the PTL and flow fields typically leads t...

Intermittency of renewable energy sources, such as wind and solar, remains as a major barrier to the establishment of a sustainable energy infrastructure (1). Balancing the supply of intermittent energy with demand requires an energy storage technology capable of operating under dynamic conditions. Over the last decade, polymer electrolyte membrane...

A stochastic modelling technique for simulating sintered titanium powder-based porous transport layers (PTLs) of the polymer electrolyte membrane (PEM) electrolyzer was developed and used to generate PTLs with varying structures and transport properties. Two stochastic parameters (seeding parameter and the filling radius) were introduced in the mod...

For the first time, pore network modelling is applied to polymer electrolyte membrane (PEM) electrolyzers. Realistic sintered titanium powder-based porous transport layers (PTLs) are generated via stochastic modelling, and we determine the influence of PTL-catalyst coated membrane (CCM) contact, pore and throat sizes, and porosity on two-phase tran...

Novel materials for gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFCs) are increasingly under investigation to improve high current performance. Metal gas diffusion layers are of interest as they provide high thermal and electrical conductivity as well as offering the possibility of integration of the flowfield and gas...

Through-plane in operando neutron radiography was used to differentiate between anode feed water and cathode water (transported through the membrane) to resolve oxygen gas bubbles in the anode. In this work, we investigated the impact of cathode purging on the electrochemical performance of polymer electrolyte membrane (PEM) electrolyzers as well a...

One of the factors leading to a decrease in the efficiency of polymer electrolyte membrane (PEM) electrolyzers is the blockage of water transport pathways through the porous transport layer (PTL). The oxygen bubbles generated from the electrochemical reaction at the catalyst layer accumulate in the PTL, impeding the transport pathways and reaction...

The stochastic modeling of sintered titanium powder-based porous transport layers in polymer electrolyte membrane (PEM) electrolyzers using information gathered from microscale computed tomography (μ-CT) is proposed. The stochastic reconstructions were compared to the μ-CT reconstruction in terms of surface morphology and structural properties. See...

Over the last century, polymer processes involving a gas or supercritical fluid (SCF) have attracted significant attention. The attributes of a gas/SCF in polymers benefited many polymer processing applications. In polymer applications, the solubility and diffusivity of the gas/SCF in polymers are important parameters. This review discusses experim...

This paper describes an innovative fiber reinforcement technology for cementitious composite structures that employs in situ shrinking microfibers to provide supplemental strength-enhancing compressive stresses. Reinforced concrete is one of the most commonly used structural materials in construction industry, primarily due to its cost, durability,...

In recent decades, electrospinning using a molten poly (ε-caprolactone) resin has gained attention for creating fibrous tissue scaffolds. The topography and diameter control of such electrospun microfibers is an important issue for their different applications in tissue engineering. Charge density, initial nozzle-exit-channel cross-sectional area,...

Encapsulated structures of poly(ε-caprolactone) microfibers were successfully fabricated through two distinct melt electrospinning methods: melt coaxial and melt-blending electrospinning methods. Both methods resulted in encapsulated microfibers, but the resultant microfibers had different morphologies. Melt coaxial electrospinning formed a dual, s...

The 14k, 45k, and 70k Mw PCL have different crystallization temperatures and therefore have slightly different characteristics affecting the fiber diameter. To observe these behaviors, the fiber was produced at every step of 10^{\circ}C for each molecular weights and the diameter was measured. Moreover, the fiber was fabricated over the cooled grou...

Development of manufacturing industry and demand for producing complex and sophisticated objects have brought up the necessity of accurate measurement, inspection, and quality control of manufactured parts. Three-dimensional scanning is a process which actualizes these requirements by registering the physical and geometrical information of the obje...

Hydrophobic surface properties are sought after in many areas of research, engineering, and consumer product development. Traditionally, hydrophobic surfaces are produced by using various types of coatings. However, introduction of foreign material onto the surface is often undesirable as it changes surface chemistry and cannot provide a long lasti...