Bipolar membranes (BPMs) are the enabling component of many promising electrochemical devices used for separation and energy conversion. Here, we describe the development of high-performance BPMs, including two-dimensional BPMs (2D BPMs) prepared by hot-pressing two preformed membranes and three-dimensional BPMs (3D BPMs) prepared by electrospinning ionomer solutions and polyethylene oxide. Graphene oxide (GO x ) was introduced into the BPM junction as a water-dissociation catalyst. We assessed electrochemical performance of the prepared BPMs by voltage–current (V–I) curves and galvanostatic electrochemical impedance spectroscopy. We found the optimal GO x loading in 2D BPMs to be 100 μg cm–2, which led to complete coverage of GO x at the interface. The integration of GO x beyond this loading moderately improved electrochemical performance but significantly compromised mechanical strength. GO x -catalyzed 2D BPMs showed comparable performance with a commercially available Fumasep BPM at current densities up to 500 mA cm–2. The 3D BPMs exhibited even better performance: lower resistance and higher efficiency for water dissociation and substantially higher stability under repeated cycling up to high current densities. The improved electrochemical performance and mechanical stability of the 3D BPMs make them suitable for incorporation into CO2 electrolysis devices where high current densities are necessary.

Bipolar membranes (BPMs) have proven useful in numerous electrochemical energy conversion and storage applications, including fuel cells and electrolyzers. However, water dissociation in bipolar membrane electrolysis cells (BPMECs) is a complicated phenomenon that occurs via several different pathways. In this work, we develop a model based on the Poisson-Nernst-Planck system that includes a multistep water-dissociation mechanism to observe the fundamental processes that contribute to BPMEC performance. The model, which is validated to in-house experimental data, demonstrates that the junction potential is the most significant contributor to the total electrolysis voltage. We investigated the effects of water-dissociation catalysts and found that the optimal catalyst pK a depends on how the catalyst is integrated into the BPM (although values near 7 are typically best, in accordance with conventional wisdom). We also simulated the water content across the BPM and found that dry-out is not a significant issue when the membrane is in contact with liquid water on both sides. The species conservation approach taken here leads to a physical understanding of the system without using any fitting parameters.

For a proton exchange membrane electrolyzer cell (PEMEC), conditioning is an essential process to enhance its performance, reproducibility, and economic efficiency. To get more insights into conditioning, a PEMEC with Ir-coated gas diffusion electrode (IrGDE) was investigated by electrochemistry and in situ visualization characterization techniques. The changes of polarization curves, electrochemical impedance spectra (EIS), and bubble dynamics before and after conditioning are analyzed. The polarization curves show that the cell efficiency increased by 9.15% at 0.4 A/cm2, and the EIS and Tafel slope results indicate that both the ohmic and activation overpotential losses decrease after conditioning. The visualization of bubble formation unveils that the number of bubble sites increased greatly from 14 to 29 per pore after conditioning, at the same voltage of 1.6 V. Under the same current density of 0.2 A/cm2; the average bubble detachment size decreased obviously from 35 to 25 μm. The electrochemistry and visualization characterization results jointly unveiled the increase of reaction sites and the surface oxidation on the IrGDE during conditioning, which provides more insights into the conditioning and benefits for the future GDE design and optimization.

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In practice, the proton exchange membrane electrolyzer cell (PEMEC) is considered to be one of the optimal hydrogen production devices with its superior compact design, high efficiency, preeminent hydrogen purity, and great compatibility with PEM fuel cells (PEMFCs). [13][14][15][16][17][18] Although the advantages of PEMECs are apparent, the high cost has been holding back its large-scale application. Precious platinumgroup metals such as Ir and Ru are mostly used as anode catalysts to withstand the aggressive anode working environment in PEMECs. [19][20][21][22][23][24][25][26][27][28][29] As reported by Ayers et al., for a practical stack with a daily production of 13 kg H 2 , the membrane electrode assembly (MEA) accounts for one quarter of the stack cost. [30] Therefore, decreasing the anode catalyst loading, simplifying anode fabrication, and cutting down electrode cost are effective strategies to reduce a PEMEC's cost and boost its commercial application.At present, a catalyst-coated membrane (CCM)/porous transport layer (PTL) design is most widely employed in PEMECs. [31,32] The great progress has been made in the research and development of CCMs to reduce catalyst loadings and to enhance long-term durability. [33,34] However, Mo et al. discovered that a large portion of the catalyst on the membrane is underutilized in the CCM/PTL design due to the conductivity limit of the ionomer mixed catalyst layer (CL). [35] They An anode electrode concept of thin catalyst-coated liquid/gas diffusion layers (CCLGDLs), by integrating Ir catalysts with Ti thin tunableLGDLs with facile electroplating in proton exchange membrane electrolyzer cells (PEMECs), is proposed. The CCLGDL design with only 0.08 mg Ir cm −2 can achieve comparative cell performances to the conventional commercial electrode design, saving ≈97% Ir catalyst and augmenting a catalyst utilization to ≈24 times. CCLGDLs with regulated patterns enable insight into how pattern morphology impacts reaction kinetics and catalyst utilization inPEMECs. A specially designed two-sided transparent reaction-visible cell assists the in situ visualization of the PEM/electrode reaction interface for the first time. Oxygen gas is observed accumulating at the reaction interface, limiting the active area and increasing the cell impedances. It is demonstrated that mass transport in PEMECs can be modified by tuning CCLGDL patterns, thus improving the catalyst activation and utilization. The CCLGDL concept promises a future electrode design strategy with a simplified fabrication process and enhanced catalyst utilization. Furthermore, the CCLGDL concept also shows great potential in being a powerful tool for in situ reaction interface research in PEMECs and other energy conversion devices with solid polymer electrolytes.