Development of advanced anion exchange membrane from the view of the performance of water electrolysis cell

Green hydrogen produced by water electrolysis combined with renewable energy is a promising alternative to fossil fuels due to its high energy density with zero-carbon emissions.Among water electrolysis technologies,the anion exchange membrane(AEM) water electrolysis has gained intensive attention and is considered as the next-generation emerging technology due to its potential advantages,such as the use of low-cost non-noble metal catalysts,the relatively mature stack assembly process,etc.However,the AEM water electrolyzer is still in the early development stage of the kW-level stack,which is mainly attributed to severe performance decay caused by the core component,i.e.,AEM.Here,the review comprehensively presents the recent progress of advanced AEM from the view of the performance of water electrolysis cells.Herein,fundamental principles and critical components of AEM water electrolyzers are introduced,and work conditions of AEM water electrolyzers and AEM performance improvement strategies are discussed.The challenges and perspectives are also analyzed.

Amplitude gradient-based metasurfaces for off-chip terahertz wavefront shaping

Metasurfaces provide an effective technology platform for manipulating electromagnetic waves,and the existing design methods all highlight the importance of creating a gradient in the output phase across light scattering units.However,in the emerging research subfield of meta-waveguides where a metasurface is driven by guided modes,this phase gradient-oriented approach can only provide a very limited emission aperture,significantly affecting the application potential of such meta-waveguides.In this work,we propose a new design approach that exploits the difference between meta-atoms in their light scattering amplitude.By balancing this amplitude gradient in the meta-atoms against the intensity decay in the energy-feeding waveguide,a large effective aperture can be obtained.Based on this new design approach,three different wavefront shaping functionalities are numerically demonstrated here on multiple devices in the terahertz regime.They include beam expanders that radiate a plane wave,where the beam width can increase by more than 900 times as compared to the guided wave.They also include a metalens that generates a Bessel-beam focus with a width 0.59 times the wavelength,and vortex beam generators that emit light with a tunable topological charge that can reach-30.This amplitude gradient design approach could benefit a variety of off-chip light shaping applications such as remote sensing and 6G wireless communications.