Discovering Reactant Supply Pathways at Electrode/PEM Reaction Interfaces Via a Tailored Interface‐Visible Characterization Cell

Abstract

electrolyzers can produce high-purity H 2 with rapid response time, which is very suitable to be integrated with intermittent renewable energy sources. PEM fuel cells can efficiently convert H 2 and O 2 to electric power for driving the next generation vehicles. CO 2 electrolyzers convert electric power to various fuels and chemical feedstocks.Many SPE electrochemical energy conversion devices involve heterogeneous reaction, which calls for efficient multiphase transport in porous transport electrode (PTE) materials. In one aspect, bad mass transport cause insufficient reactant supply and product blockage on the reaction interfaces, finally leads to a depressed energy conversion efficiency. [12][13][14] Although, some publications reported that the gas product may introduce local microconvection to enhance the reactant supply in liquid electrolyte system. [12,15,16] Considering the solid state of SPE, the micro-convection impacts are supposed to be limited. In another aspect, mass transport in PTE materials has great impacts on reaction selectivity in some competing reaction. [17] For example, Xia et al., found that increasing the local O 2 concentration can greatly enhance the Faraday efficiency of H 2 O 2 production. [18] Optimizing porous transport materials is a good way to enhance mass transport in SPE electrochemical energy conversion devices. Researchers develop various porous transport layers (PTLs) or gas diffusion layers (GDLs) to enhance the multi-phase mass transport from the flow field to the reaction interface, including fiber based GDLs/PTLs, [19] powder based GDLs/PTLs, [20] mesh based GDLs/PTLs, [21] or some tailored GDLs/PTLs. [22,23] In addition to mass transport in PTLs/GDLs, the mass transport in PTE/SPE interface is more essential for SPE based energy conversion devices. Because the PTE/SPE interface is closer to reaction sites. However, due to the limited in situ mass transport characterization methods, the mass transport at PTE/SPE interface is overlooked. In situ electrochemistry characterizations, including polarization curve measurements, electrochemical impedance spectroscopy, or high frequency resistance measurements, are widely used to characterize the overall performance of PEMECs, and reflect some overall mass transport properties. But these characterizations can't describe

Universal Approach to Direct Spatiotemporal Dynamic In Situ Optical Visualization of On‐Catalyst Water Splitting Electrochemical Processes

“…[42][43][44] Zhang et al performed the micro-scale investigation of electrochemical cells and provided insights on reaction interface optimization and mass transport optimization by visualizing the gas bubbles during the water-splitting reaction. [45][46][47] Despite these research efforts and advancements in the field during the past decades, scarce efforts have been made toward the chemical moiety-specific visualization/imaging of the water-splitting electrochemical reactions. It is to be realized that in this work fluorescence imagining of the electrochemical cell has been performed which gives insights about the chemical changes in the electrochemical system rather than relying on the "optical visualization" which is blind to any chemical changes in the system.…”

“…[42][43][44] These in situ experiments provided insights on reaction interfaces and mass transport optimization by visualizing the gas bubbles during the water-splitting reaction. [45][46][47] However, it is to be realized that this "bubble-based" visualization of water splitting reaction is limited due to the blind nature toward any chemical change happening in the electrochemical cell and thus necessitates innovative avenues that can visualize any chemical changes "even selectively" during any electrochemical reaction. In this work, for the first time, direct spatiotemporal dynamic in situ optical visualization of on-catalyst water splitting processes is performed under neutral conditions by exploiting the exceptional fluorescent properties of the HPTS probe.…”

Recent advances in proton exchange membrane water electrolysis

“…55 Through transparent modification of cell components, an interface-visible characterization cell was developed using HMVS to display the vivid electrochemistry phenomena and mass transport in electrode/PEM interfaces. 56 The visible water/gas dynamics (such as gas blockage in LGDL and additional water dynamics on the PEM) would advance the interface chemistry in the PEMWE. It is noted that efforts are still required to perform the operando characterizations under real working conditions.…”