Atomic-scale quantification of hydrogen in metal hydrides by electron ptychography.

Direct visualization of hydrogen-the smallest and lightest element-in complex materials remains a fundamental challenge. Owing to its extremely weak electron scattering, high mobility, and the resolution limits of conventional transmission electron microscopy, the atomic-scale occupation sites and spatial distribution of hydrogen have remained largely inaccessible. Here, we demonstrate atomic-resolution imaging and quantitative analysis of hydrogen in metal hydrides using energy-filtered multislice electron ptychography (MEP). By applying MEP to a complex high-entropy alloy (HEA) hydride, we resolve previously inaccessible structural details, including picometer-scale hydrogen displacements and pronounced three-dimensional inhomogeneity. Statistical analysis further reveals that hydrogen incorporation unexpectedly suppresses the intrinsic lattice distortion present in the pristine HEA. These results establish MEP as a powerful platform for quantitative hydrogen imaging at the atomic scale and provide direct insight into the structural role of hydrogen in phenomena ranging from hydrogen embrittlement and hydrogen storage to emergent electronic phase transitions.