Three-Dimensional Numerical Simulation of the Performance and Transport Phenomena of Oxygen Evolution Reactions in a Proton Exchange Membrane Water Electrolyzer.

Proton exchange membrane (PEM) water electrolysis, which is one of methods of hydrogen production with the most potential, has attracted more attention due to its energy conversion and storage potential. In this paper, a steady state, three-dimensional mathematical model coupled with the electrochemical and mass transfer physical fields for a PEM water electrolyzer was established. The influence of the different operation parameters on the cell performance was discussed. Moreover, the different patterns of the flow field, such as parallel, serpentine, multi-serpentine, and interdigitate flow fields, were simulated to reveal their influence on the mass transfer and current distribution and how they consequently affected the cell performance. The results of the numerical modeling were in good agreement with the experimental data. The results demonstrated that a higher temperature led to a better mass transfer, current distribution, and cell performance. By comparing the polarization curve, current, velocity, and pressure distribution, the results also indicated that the PEM water electrolyzer with a parallel flow field had the best performance. The results in this study can help in optimizing the design of PEM water electrolyzers.

Discovery of true electrochemical reactions for ultrahigh catalyst mass activity in water splitting.

Better understanding of true electrochemical reaction behaviors in electrochemical energy devices has long been desired. It has been assumed so far that the reactions occur across the entire catalyst layer (CL), which is designed and fabricated uniformly with catalysts, conductors of protons and electrons, and pathways for reactants and products. By introducing a state-of-the-art characterization system, a thin, highly tunable liquid/gas diffusion layer (LGDL), and an innovative design of electrochemical proton exchange membrane electrolyzer cells (PEMECs), the electrochemical reactions on both microspatial and microtemporal scales are revealed for the first time. Surprisingly, reactions occur only on the CL adjacent to good electrical conductors. On the basis of these findings, new CL fabrications on the novel LGDLs exhibit more than 50 times higher mass activity than conventional catalyst-coated membranes in PEMECs. This discovery presents an opportunity to enhance the multiphase interfacial effects, maximizing the use of the catalysts and significantly reducing the cost of these devices.