EDX Array Tomography: 3D Imaging With Chemical Sensitivity and Submicron Resolution Through Ultramicrotomy and SEM-EDX Mapping

Elemental contrast from energy-dispersive X-ray spectroscopy (EDX) provides valuable insights into various materials and samples. However, this surface-mapping technique suffers from poor depth resolution, which prevents a straightforward application to tomographic reconstruction. Additionally, due to charge artifacts or beam damage, this technique is often limited to electrically conductive samples, which does not allow its use on multiphase samples with low conductivity and complex 3D geometries. We developed an adaptation of array tomography using an automated tape-collecting ultramicrotome (ATUMtome) and scanning electron microscopy with EDX mapping to enable tomographic imaging of polymer-containing multiphase samples at submicron resolution. Hence, this method overcomes the limited depth resolution of EDX mapping, and by surface-coating the sections before imaging, charging artifacts are mitigated. Recently, we demonstrated the utility of the technique by applying it to a multiphase microporous layer encountered in a CO2 electrolyzer gas diffusion electrode, which could not be imaged using conventional tomographic approaches. A digital model of the full electrode was obtained in combination with focused ion beam scanning electron microscopy tomography and X-ray microtomography. Here, we describe the process of EDX array tomography in detail and elucidate the advantages of the technique in the field of energy materials.