Incidental\nand Intentional Transformation:\nTransition Metal Pnictide and Chalcogenide\nElectrocatalysts for Alkaline Hydrogen Evolution

Transition metal pnictides and chalcogenides (X-ides)\nhave been\nstudied as promising electrocatalysts for the alkaline hydrogen evolution\nreaction (HER). These materials often undergo dynamic transformations,\neither on their surface or within their bulk, occurring “incidentally”\nduring the HER or “intentionally” through electrochemical\nactivation. Current research shows that X-ides can remain unchanged,\nundergo oxidation or reduction, or transform into different X-ides\nwith reduced X-ogen (i.e., chalcogen or pnictogen) to metal ratios\ncompared to their original forms. In this Focus Review, we explore\nexamples of these transformations for incidental and intentional cases,\nidentify gaps in current knowledge, discuss divergent views on the\nnature of catalytically active species, and provide recommendations\nfor more accurate identification of the active HER species in future\nstudies.