Direct Observation of Tantalum Nitride Photoelectrode Degradation by Environmental Transmission Electron Microscopy

This multistimulus configuration enables real-time atomic-scale imaging of PEC materials under conditions closely resembling operation. Applying this platform to Ta₃N₅, we directly capture its structural evolution under combined stimuli and reveal a previously unresolved degradation pathway involving nanocrystal detachment, migration, and inward-propagating amorphization. These processes lead to the growth of amorphous surface layers that are directly associated with performance loss in operating photoanodes.

More broadly, this work establishes a mechanistic framework linking nanoscale structural transformations to macroscopic device degradation, providing concrete targets for stabilization strategies in Ta₃N₅ and related metastable PEC materials. In addition, the results demonstrate the broader potential of multistimulus ETEM for investigating complex degradation phenomena in functional energy materials.