  As hydrogen is touted as a key player in the decarbonization of modern
society, it is critical to enable quantitative H analysis at high spatial
resolution, if possible at the atomic scale. Indeed, H has a known deleterious
impact on the mechanical properties (strength, ductility, toughness) of most
materials that can hinder their use as part of the infrastructure of a
hydrogen-based economy. Enabling H mapping, including local hydrogen
concentration analyses at specific microstructural features, is essential for
understanding the multiple ways that H affect the properties of materials,
including for instance embrittlement mechanisms and their synergies, but also
spatial mapping and quantification of hydrogen isotopes is essential to
accurately predict tritium inventory of future fusion power plants, ensuring
their safe and efficient operation for example. Atom probe tomography (APT) has
the intrinsic capabilities for detecting hydrogen (H), and deuterium (D), and
in principle the capacity for performing quantitative mapping of H within a
material's microstructure. Yet the accuracy and precision of H analysis by APT
remain affected by the influence of residual hydrogen from the ultra-high
vacuum chamber that can obscure the signal of H from within the material, along
with a complex field evaporation behavior. The present article reports the
essence of discussions at a focused workshop held at the Max-Planck Institute
for Sustainable Materials in April 2024. The workshop was organized to pave the
way to establishing best practices in reporting APT data for the analysis of H.
We first summarize the key aspects of the intricacies of H analysis by APT and
propose a path for better reporting of the relevant data to support
interpretation of APT-based H analysis in materials.
