Nature Energy, Published online: 10 June 2026; doi:10.1038/s41560-026-02089-4

Electrocatalytic surfaces are dynamic, but few methods correlate nanometre-scale current with structure across large areas. Interferometric electro-optical microscopy now images electrochemical currents at 50 nm and 10 ms resolution, revealing that hydrogen evolution on MoS2 initiates and propagates along specific crystallographic directions.