No abstract

The increasing use of intermittent renewable energy sources calls for novel approaches to large-scale energy conversion and storage. Hydrogen can be readily stored and produced from renewable sources using polymer electrolyte membrane water electrolysers (PEMWEs). Mass transport of water and product gas in the liquid-gas diffusion layer (LGDL) is critical for PEMWE performance, particularly at high current densities. In this work, neutron radiography is deployed to measure the spatial distribution of water within three different LGDLs, while X-ray micro-computed tomography (XCT) is used to characterize the microstructure of the LGDL materials. The combination of these two techniques yields valuable insight into water transport within the LGDL. Significant local water heterogeneity is observed and a link between flow-field geometry/location and LGDL mass transport is identified. It is further shown that the pore volume in these LGDLs is significantly under-utilized, pointing the way towards design optimisation of LGDL materials and architectures.

No abstract

Polymer electrolyte membrane water electrolysers (PEMWE) are a key technology for producing clean ('green') hydrogen for decarbonisation of the transport sector and grid stabilization utilising increasing levels of renewable energy. Understanding the complex interplay of factors that affect device operation is key to improving the technology and advanced diagnostic techniques have a major role to play. In this work, acoustic emission analysis is used as a non-destructive, operando diagnostic tool to provide information about the relative number and size of gas bubbles generated locally within a PEMWE, providing effective characterization of the local flow regime. An optically transparent single-channel PEMWE is used to investigate the relationship between the acoustic signals obtained and the two-phase flow conditions inside the cell. Results show good correlation between the number of acoustic 'hits' and the number of bubbles passing through the flow channel. The size of bubbles is also shown to affect the average frequency of the hits. Consequently, the transition between flow regimes can be identified by acoustic emission analysis, paving the way for a simple, low-cost, nondestructive means of mapping flow inside commercial-scale PEMWEs.

In academic labs, most oxygen evolution reaction studies are carried out in conventional three-electrode cell set-ups; however, this configuration may not accurately represent conditions experienced under practical electrolyser conditions.